GEO'98 Abstracts

GEO'98 Abstracts

Integration of Geology and Geochemistry into Basin Modeling and Exploration Risk Analysis: Case Study from Central Saudi Arabia

Mahdi A. Abu-Ali, James E. Lacey, Adry K. Bissada Houston Advanced Research Center and Jim G. McGillivray, Saudi Aramco

This study involves a new approach for play/prospect James E. Lacey has been a Senior evaluation that combines basin modeling technology with Research Scientist for the Houston risk analysis. In this method geologic and geochemical data Advanced Research Center since are integrated to develop a probabilistic estimation of oil September 1995. He previously and gas reserves. worked for 28 years for Texaco in exploration research and for three The process estimates oil and gas generated and expelled years as a development geologist for by comparing the organic richness, maturity, kerogen type Chevron. James received his BSc and and other factors with the results of a very large number of MSc degrees from the University of basin modeling runs. The hydrocarbon charge arriving at Pittsburgh and a PhD degree from the the trap is computed by subtracting from the expelled University of Illinois. His current interests include the hydrocarbons the amounts leaked, retained by the carrier, application of risk analysis to exploration and or dissolved in the formation water. Due to the inherent the development of geochemical techniques to allocate uncertainties in estimates of the relevant data, the technique commingled production streams to specific sources. inputs most likely values and probable ranges. Finally, the volume of hydrocarbons trapped is set equal to the lesser Adry K. Bissada is a Senior Research amount of either trap capacity or hydrocarbon charge. Scientist and Director of the Results are expressed as the mean and median reserves, the Geochemistry Unit at the Houston probability of reserves greater or less than critical economic Advanced Research Center. He holds thresholds, and the possible range of reserve values. This an MSc degree in Geology/ process can provide a powerful tool for high-grading Geophysics and a PhD in Geology/ exploration prospects in terms of the desired combination Geochemistry, both from Washington of reserves potential and exploration risk. In this paper, University in St. Louis. He has 30 details of the process will be highlighted and illustrated by years experience in the petroleum examples from Central Saudi Arabia. industry. Adry has published numerous papers on principles and practice of geochemistry Mahdi A. Abu-Ali is a Geologist/ in exploration and production operations, and lectured Geochemist with the Regional extensively around the world on many aspects of petroleum Mapping Group of Saudi Aramco. geochemistry. He has developed a variety of geochemical He has 13 years of experience in tools and processes for which four patents have been issued. exploration and basin analysis studies. His areas of interest include Jim G. McGillivray is currently in- hydrocarbon generation and charge of the Regional Mapping migration modeling, geologic Group with Saudi Aramco. He has 27 mapping and exploration risk years of petroleum and exploration analysis. Mahdi is affiliated with the industry experience represented by AAPG, EAOG, and ACS. He holds BSc and MSc degrees in 12 years with Chevron Standard Industrial Chemistry and Geochemistry from King Fahd Limited and Wainoco Oil and Gas University of Petroleum & Minerals, Saudi Arabia and the Limited in Canada, and 15 years with Colorado School of Mines, USA, respectively. Mahdi has Saudi Aramco. Jim has BSc and MSc published and presented several papers on the Paleozoic degrees in Geology from McGill petroleum system of Saudi Arabia. University.

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Geological Reconstruction of the Jean-Luc L. Rudkiewicz is Project Leader for Pilot Studies in Basin Paleozoic Hydrocarbon System, Evaluation with Institut Français du Central Saudi Arabia Pétrole (IFP) in Rueil-Malmaison, France. He completed a PhD from Mahdi Abu-Ali, Saudi Aramco the Paris School of Mines in 1989. Jean-Luc L. Rudkiewicz, Starting in 1987, his initial research Institut Français du Pétrole focused on stochastic modeling of Jim G. McGillivray, Saudi Aramco heterogeneous reservoirs. Since and Françoise Behar 1992, Jean-Luc has been involved in Institut Français du Pétrole compositional modeling of generation and migration of hydrocarbons in sedimentary basins. He currently applies In this paper an integrated geochemical model is developed IFP’s basin modeling tools to basins worldwide, in for the Paleozoic oil and gas system of Saudi Arabia. The cooperation with industrial partners. generation and migration history has been reconstructed through geologic time to assess gas and oil expulsion, Françoise Behar is Project Leader migration, entrapment and future exploration potential. with Institut Français du Pétrole for compositional modeling of The Paleozoic oil and gas system in Central Saudi Arabia hydrocarbon generation and consists of the Lower Silurian Qusaiba Hot Shale as the degradation in sedimentary basins. major source rock and the Permian Unayzah sandstone as She completed a PhD in Geology the main regional reservoir. To reconstruct the hydrocarbon from the University of Paris in 1978 generation, immature and mature source rock samples were and a PhD in Chemistry from the recovered, and their compositional kinetics were determined. University of Strasbourg in 1982. The gas potential of the most immature sample amounts to Françoise joined IFP in 1982 and 101 mg/g Total Organic Carbon (TOC), compared to an oil currently works on kinetics of oil and gas generation in potential of 384 mg/g TOC. The thermal regime and source rocks and thermal stability of the hydrocarbons in migration directions were reconstructed through time using reservoirs. a 3-D data set comprising the major formations from Paleozoic to Cenozoic over the 480 by 550 kilometer study area. Present day bottom hole temperatures and past maturity indicators were used for calibration. The 3-D data First Results of 3-D Seismic Prospecting, set was then backstripped to reconstruct paleoslopes for all Onshore Azerbaijan Republic layers, with special emphasis on the Unayzah and Qusaiba formations. Ibrahim D. Akhundov Socar The expulsion history of the Qusaiba source rock shows a peak expulsion younger than 52 million years, with a The Azerbaijan Scientific Research Institute of Geophysics significant amount of gas being created from secondary has developed a new technique for seismic prospecting cracking of oil retained in the source rock. Paleostructure which was tested in Jafarly and Nasibbeyli in onshore of the Unayzah reservoir and associated capture areas were Azerbaijan. The technique is suitable in conditions of computed at different times, especially after peak expulsion. complex topographic relief and is based on a non-standard The expelled amounts of hydrocarbons from the Qusaiba system for areal observations on profiles of arbitrary form. source rock were then added up to rank the different The processing of the data includes 3-D time migration and structures according to their charge volume and the nature the data is presented in depth. of trapped components. This highlighted the most promising structures for more detailed review of future exploration. In the areas of Jafarly and Nasibbeyli, the exploration play is a stratigraphic trap in the top of the Mesozoic which Mahdi A. Abu-Ali and Jim G. McGillivray (see abstract pinches out below a thick series of Miocene-Pliocene "Integration of Geology and Geochemistry into Basin deposits. The play was initially defined with 2-D seismic Modeling and Exploration Risk Analysis: Case Study from lines acquired by Azneftegeofizika which imaged the top of Central Saudi Arabia" on page 38 for biographies and the Mesozoic pinch out. The distribution of the pinch-out photographs) was mapped using the new technique on 3-D seismic data. The 3-D survey also increased the areal distribution of the exploration target.

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Ibrahim D. Akhundov is currently Head of the Laboratory of Total The Heavy Oil /Tar Mat in Minagish Field, Seismic Prospecting at Azerbaijan Kuwait: Detection, Characterization and Geophysical Scientific Research Impacts on Reservoir Performance Institute of the state oil company of Azerbaijan Republic. Ibrahim Hamad Al-Ajmi, Ram S. Gaur graduated from Azizbekov Industrial Kuwait Oil Company Institute, Azerbaijan, in 1957. He has and Andrew Brayshaw 40 years experience in formulation British Petroleum, Kuwait techniques and processing 2-D and 3-D seismic surveys. He is a member of the National In common with many giant oil fields worldwide, the Committee of Azerbaijan Geophysicists. Minagish field (Minagish Oolite Formation) in Kuwait has an areally extensive and variable thickness, heavy oil zone at the base of the oil column. The heavy oil zone, or tar mat, is thought to represent a partial permeability barrier between The Impact of 3-D on the aquifer and oil leg, but its fieldwide effect and properties Field Development: Case History from are unknown. As the Minagish field undergoes full-field the Warad Field, Oman waterflood, understanding the distribution and properties of the heavy oil zone is critical to planning whether to inject Talib A. Al-Ajmi water above the tar mat - with unavoidable reserve losses - Petroleum Development Oman or inject into the aquifer directly beneath where the tar mat is poorly developed. Full field 3-D modeling was undertaken to enhance the understanding of the reservoir architecture of complex Difficulty in discriminating between cemented and sandstone reservoirs in the Warad field of south Oman. The bituminous intervals on electric logs has lead to the adoption 3-D modeling has investigated the major geological of new geochemical techniques (Iatroscan) to detect the uncertainties associated with the calstic reservoirs of the presence and thickness of the heavy oil zone. Analyses sheetflood Mahwis and the glacial Al Khlata formations. indicate that the tar mat is characterized by a high proportion Scale and continuity of calcite cemented zones and shales of asphaltenes, but low concentration of saturates, polars including faulting have been tested through multiple and aromatics. The Minagish heavy oil zone/tar mat is scenarios in various simulation models to assess aquifer interpreted to be the result of de-ashphalting as opposed to pressure support. Modeling has revealed that low gravity segregation. Compositional variations through the productivity characterizes the vertically heterogeneous oil column have been mapped in Minagish using Mahwis reservoir sands. These sands are dominated by geochemcial parameters measured on samples. A predictive vertically stacked stochastic shales with low vertical model for API gravity and live oil viscosities has been permeability. High production associated with high water established for Minagish, together with a model for tar mat cut is typical of the homogeneous lower member of Al Khlata occurrence and thickness. New understanding of the tar mat, Formation and is due to the high vertical and horizontal its genesis and spatial distribution has helped in developing permeability of the reservoir sands and conductive fractures. a water injection strategy that maximizes recoverability in As a result, the field development plan includes 12 horizontal Minagish. This information will also play a key role in multi-lateral wells in areas of high Kv/Kh and 10 deviated determining ways to liberate oil held within the heavy oil (high angle) wells in areas of low Kv/Kh to ensure zone. penetration of the full suite of reservoir units. Hamad Al-Ajmi is currently a Talib A. Al-Ajmi is currently a Geologist with Kuwait Oil Company Production Geologist for Petroleum with 6 years experience. He holds a Development Oman, working on the BSc in Geology from Kuwait Amin and Warad fields. He holds a University and has worked on a BSc degree in Geosciences from the range of fields in Kuwait as a University of Arizona. Talib has been Petrophysicist and later as a working with Petroleum Development Geoscientist. He also Development Oman for the last seven has experience working in the North years. He is an SPE member. Sea, playing a role in the Bruce field development whilst on secondment to British Petroleum. His primary area of expertise is in field development, formation evaluation and permeability modeling. He is an active member of the AAPG.

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Ram S. Gaur has 37 years Impact of 3-D Seismic Surveys on experience in development geology and reservoir engineering. He is a Minagish and Umm Gudair Fields Senior Development Geologist with Development, Kuwait Kuwait Oil Company (KOC) since 1979. Ram holds an MSc from BHU Alaa M. Al-Ateeqi and Dave G. Foster India. Prior to joining KOC he Kuwait Oil Company worked for ONGC India for 19 years in the Petroleum Research Institute In 1996 Kuwait Oil Company started to acquire a massive teaching graduates in development program of both 2-D and 3-D seismic data, believed to be geology and reservoir engineering developing new oil fields. one of the largest in the region. The 2-D survey was aimed At KOC he has worked on reservoir and development studies at defining possible prospective areas, while the 3-D surveys of all producing reservoirs, geological operations and are aimed at achieving increased productivity of the existing training of Kuwaiti professionals. He is an active member oilfields. The 3-D surveys acquired over the Minagish and of the SPE. Umm Gudair fields in the west region of onshore Kuwait were two of the first 3-D surveys to be completed. Andrew Brayshaw is currently a Senior Technical Advisor for BP The 3-D data is of excellent quality, showing very high Exploration, seconded to Kuwait Oil signal-to-noise ratios, and having stable phase and amplitude Company. He has 13 years characteristics. The rapid interpretation of these 3-Ds has experience with BP in exploration, been enabled by state-of-the-art interpretation and development geoscience and visualisation software at Kuwait Oil Company, and has commercial evaluation of reservoir already had a considerable impact on the perception of the developments. He has worked subsurface geology of the mainly Cretaceous reservoirs. variously in Qatar, Egypt, Papua Fault patterns have been reliably defined on both fields for New Guinea, Norway, Azerbaijan the first time. Accurate depth maps have been achieved and Alaska. His primary area of expertise is new field through the superior 3-D image, together with careful developments and reservoir management. He holds BSc attention to statics corrections and depth conversion. This and PhD degrees from the University of London, and a allows accurate well placement. Acoustic impedance fellowship in engineering at the University of Florence, Italy. inversion is being used to define reservoir and aquifer porosity. The impact of the 3-D surveys is to enable optimum development decisions to be made, thus maximizing the value of Kuwait’s valuable oil resources. 3-D Seismic Survey Design Parameters Alaa M. Al Ateeqi received his BSc Habib Al-Alawi in Geology from Kuwait University Bahrain National Oil Company in 1993 and joined Kuwait Oil Company in September of the same The design stage is an important step in planning the year. Alaa worked as a well-site acquisition, processing and interpretation of a 3-D seismic geologist for one year before joining survey. A computer program was written to calculate design the Geophysics Division as a seismic parameters such as fold, bin size, maximum and minimum interpreter, where he was initially offsets, vertical and lateral resolution. The program was seconded to Exxon working on used to evaluate survey design on the Bahrain field. exploration assignments. He is currently part of the West Kuwait Fields Seismic Habib Al-Alawi acquired a BSc Interpretation Team, focusing on the Umm Gudair field. degree in Physics from Bahrain University in 1989. Habib worked Dave G. Foster has worked for as a Teaching and Research Assistant British Petroleum since 1981 when with the same University between he received his BSc in Geology with 1989 and 1994. He joined Bahrain Geophysics from Leicester National Oil Company's Exploration University. He has extensive 2-D and Team in July 1994 as Exploration 3-D seismic interpretation Geophysicist, working mainly on the experience, and has occupied posts interpretation of seismic data. in Tunisia, the North Sea, onshore UK, Egypt, Canada, and the . Dave is currently seconded to the Kuwait Oil Company, where he is West Kuwait Fields Seismic Interpretation Team Leader. 42

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Integrating Fluid Flow and George A. Grover is a Reservoir Geologist in the Geological Borehole Imaging Data in Fracture Department at Saudi Aramco. Characterization, Hanifa Reservoir, George was previously a Research Abqaiq Field, Saudi Arabia Geologist with Chevron Petroleum Technology Company, La Habra, Haider H. Al-Awami, George A. Grover, California (1985-1990), and an Rick Davis, Saudi Aramco Exploration Geologist with Gulf Oil Sait I. Ozkaya and Joerg E. Mattner Company, Texas (1981-1985). He Western Atlas International holds a PhD in Geology (1981) from Virginia Tech. The Hanifa reservoir at Abqaiq field, eastern Saudi Arabia, consists of microporous lime-mudstone (average porosity Rick Davis earned a BSc in Geology 17%) with low matrix permeability (average 1 mD). from the University of Texas at Austin Borehole (core, image log, flow profile) studies, in and did graduate work at Colorado conjunction with 3-D seismic interpretations, indicate that School of Mines. Rick worked both the Hanifa reservoir is pervasively fractured. Recent on exploration and development integration of fluid flow profiles with detailed interpretations projects in the Rocky Mountains, mid- of borehole image logs, from seven horizontal wells and one continent and eastern US for 13 vertical well, indicate that two conductive fracture types can years. Since 1986 his work has be distinguished. (1) Fracture swarms are from 100 meters centered on reservoir characterization up to several kilometers long, have a dominant east-northeast and modeling, working on the strike and an average spatial separation of 600 meters between Anschutz Ranch East field (Utah-Wyoming Thrust Belt) for swarms. (2) Stylolitic-fractures are densely-clustered, the Anschutz Corporation, and working on the Ghawar and centimeter- to decimeter-high, tension gashes, emanating Abqaiq fields for Saudi Aramco. from stylolites, with an areal density of at least 7 million fractures per square kilometer. The former are called 'super Sait I. Ozkaya holds a MSc degree fractures' since they contribute 75% to 100% of wellbore in Computer Science, Mining fluid flow when encountered. The latter stylolitic fractures Engineering and a PhD in Geology. occur mainly in the upper and lower parts of the reservoir. His experiences include field geology The density of the stylolitic fractures shows an inverse and regional tectonics, statistical and relationship with porosity. Production logs suggest that only computer studies in geology. He has a minor flow is contributed from stylolitic fractures. developed computer software for various applications such as Fracture length distributions reveal that 30% of the 'super balanced cross-section construction, fractures' could extend through the overlying Jubaila and finite element solution of fluid Formation and into the Arab-D reservoir. Well test analysis, flow and stress. At present Sait is working on fractured numerical reservoir simulations using both dual- and single- reservoir characterization. In particular, he is interested in porosity models, 3-D seismic mapping of faults at various modeling fracture networks and simulation of fluid flow horizons and horizontal drilling have confirmed the existence through fractures. of fault communication between the Arab-D and Hanifa reservoirs. The implications of this faulting on depletion Joerg E. Mattner is currently strategies of the Hanifa reservoir in conjunction with the Manager of Western Atlas depletion of the overlying Arab-D reservoir are discussed. Geoscience Center in Bahrain. He graduated in Geology in 1986 and Haider H. Al-Awami is General received his PhD in 1990 from Supervisor, Abqaiq Area Reservoir Clausthal University, Germany. Management with Saudi Aramco. He During his studies and subsequent joined Saudi Aramco in 1976 and teaching assignment, Joerg worked worked in production, drilling and mainly on geological projects in reservoir engineering until 1980 Europe, South America and Northern when he had a one year overseas Canada. He joined the Petrophysical Evaluation Group of assignment with Exxon Production Western Atlas International in London in 1990. Joerg was Research Company in Houston. He assigned to Syria to establish a log analysis center in 1991, became General Supervisor of and in 1994 he became the Chief Geologist for the Middle Reservoir Engineering in 1985. Haider received a BSc East. degree in in 1977. He is professionally interested in Reservoir Engineering, Economics and Geology. 44

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numerous mature fields on Alaska’s North Slope and around Sedimentology to 3-D Geological Model, the world. Currently, he is leading the multi-disciplinary Impact on Reservoir Development team that is focusing on the development plans of the Upper Upper Burgan Reservoir, Burgan reservoir in Kuwait. Northern Kuwait Roger Davies has 17 years Ahmad J. Al-Eidan, Kuwait Oil Company experience in the oil industry. He was William B. Wethington, BP Kuwait employed by British Petroleum as a and Roger Davies Sedimentologist from 1980 to 1994. Badley, Ashton and Associates, UK Since 1994, Roger has worked as a Consultant, and is an associate of The Aptian-Albian Upper Burgan reservoir is a major Badley, Ashton & Associates and the productive interval in both the Raudhatain and Sabriyah Energy Resource Alliance. He has fields, located in northern Kuwait. This reservoir represents been involved in the description of a complex series of heavily bioturbated shallow marine clastic and carbonate reservoirs in sandstones and nested valley fill channels. many parts of the world including the North Sea, Alaska and the Middle East. Roger has a PhD from the University The Upper Burgan reservoir is targeted to increase its current of Southampton. production by more than five times, culminating with a plateau rate of 120,000 bopd. The dramatic increase in production will be achieved through the application of a Dual-Sensor Bottom Referenced fieldwide waterflood development program. Phase 1 is scheduled to begin in 1999. Acquisition and Processing Results

A comprehensive and focused geological study has been Issam Al-Esmar, Mahfoudh Al-Ginaibi conducted on the reservoir. The study includes petrographic Abu Dhabi National Oil Company analysis, core description, image log analysis, 3-D seismic and Abu Baker Al-Jeelani and sequence stratigraphy which has been integrated with Abu Dhabi Company for Onshore Oil Operations all available dynamic data to best define the reservoir architecture and therefore, flow units. A fine grid 3-D The dual-sensor technique employs sea-bed located receiver geological model has been built to further aide in stations containing co-located hydrophones and geophones. visualization, data quality and for input into simulation. The combination of signals recorded from the co-located bottom referenced hydrophone/geophone pairs has resulted The geological analysis has had significant impact on the in an increase in the bandwidth of the recorded seismic reservoir development strategy by influencing waterflood wavelet relative to that achieved with towed streamers. This strategy, pattern orientation and expected performance. resolution is derived from an increase in both the low and high frequency content of the wavelet resulting from the Ahmad J. Al-Eidan received a BSc dual-sensor combination. degree in Geology from Kuwait University in 1992 and joined Kuwait The increased wavelet resolution is maintained through the Oil Company in January of 1993. acquisition process by acquiring the data through a stationary Ahmad worked as Wellsite Geologist receiver spread. Compared to streamer acquisition, where for three years, after that joined Field cable feather acts to produce mid and far offset midpoints Development Department as from out of the plane of a 2-D line, the midpoints generated Development Geologist. from shooting into a fixed receiver spread are more tightly clustered along the axis of the line. This clustering acts to reduce the effect of wavelet “smearing” which occurs when traces in a Common Mid-Point (CMP)gather are distributed William B. Wethington received a along dipping surfaces. BSc degree in Geology in 1985 and a MSc degree in Energy and Mineral A fixed receiver spread also allows a great deal of flexibility Resources from the University of in acquisition geometry design and thus control of the Texas at Austin in 1989. William's geometric attributes of the traces incorporated into each major interests include development CMP location. This flexibility allows survey designs to meet geology applications to field the spatial sampling requirements for wave equation-based development and reservoir data processing such as Dip Moveout and migration. management. He has worked in

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A test line was recorded with dual sensor seismic data for Squeezed Integral DMO for the ADNOC/A/B tie line project in the autumn of 1996. The line extended for 45 kilometers in water depths ranging Depth Variable Velocity: from 3 to 23 meters. The two main objectives of the project A Case History in Saudi Arabia were an evaluation of any apparent increase in seismic bandwidth from the combination of hydrophone and Mohammed N. Al-Faraj, Peter C. Green geophone signals and the use of seismic first break and Anthony A. Sirtautas information to determine the sea-floor location of the dual- Saudi Aramco sensor packages. In seismic data processing, the dip moveout (DMO) process Examination of the receiver positions computed from the is known to be relatively insensitive to velocities, especially seismic first breaks show that, on average, the receivers were when velocity does not change rapidly with depth. In fact, within 5 meters of the drop positions with an average in- the DMO process is totally velocity-independent when the line difference of about 3 meters. Processing of the seismic medium velocity is constant, a situation not likely to occur data shows that there is an increase in bandwidth and in nature. [Deviation from constant velocity, is a measure whitening of the signal spectra for the dual sensor data that can determine the reliability of constant-velocity DMO relative to data recorded from hydrophones only. (CV-DMO) processing.] When velocity varies moderately with depth, CV-DMO will typically produce reasonable Issam Al-Esmar received his MSc results. This could explain why the popular CV-DMO has degree in in been successfully applied in different areas of the world for 1977 from the Institute National des many years. Hydrocarbon, Algeria. He is currently Exploration Geophysicist with Abu In this paper, we modify Hale’s CV-DMO integral method Dhabi National Oil Company to approximately handle velocity variations with depth by (ADNOC). Prior to joining ADNOC, squeezing the CV-DMO operator. We first present synthetic Issam worked with , examples comparing CV-DMO with squeezed DMO. We Algeria between 1977 and 1983. He then show the results after applying this squeezed DMO is a member of the SEE. algorithm to a 3-D seismic dataset in Saudi Arabia, and compare them to results obtained without squeezing. Mahfoudh Al-Ginaibi received a BSc degree in Geophysics from United We conclude that the DMO process must be “velocity- Arab Emirates University in 1983. tweaked”, in some areas of Saudi Arabia, in order to improve He has been with Abu Dhabi National data imaging. A cheap and efficient way of achieving this Oil Company since 1983 where he is is to apply the Hale’s squeezing method to an existing Geophysics Supervisor of 2-D/3-D constant-velocity integral method. In our case, we conclude Acquisition and Processing. that squeezed DMO was able to enhance data quality, in Mahfoudh is a member of the SEE areas of interest, where CV-DMO failed. and EAG. Mohammed N. Al-Faraj received a BSc degree in Electrical Engineering Abu Baker Al-Jeelani received a BSc from the University of Wisconsin- in Geophysics from United Arab Milwaukee in 1983, and an MSc and Emirates University in 1983. He a PhD in Geophysics from the worked with Abu Dhabi National Oil Colorado School of Mines in 1987 Company as Geophysics Supervisor and 1993, respectively. Since 1984, between 1983 and 1996. Abu Baker Mohammed has been with Saudi is currently a Team Leader with Abu Aramco, Saudi Arabia. His interests Dhabi Company for Onshore Oil include seismic data processing, Operations. He is a member of the vertical seismic profiling, reservoir characterization, and SEG, SEE and EAG. working in multi-disciplinary teams. Currently, Mohammed is in charge of all 3-D seismic processing in Saudi Aramco, and is the president of the Dhahran Geological Society. He is a member of the SEG, DGS and EAGE.

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Peter C. Green is Geophysicist with campaign, acquiring some 6,000 kilometers of seismic data Saudi Aramco's Geophysical and, in 1983-84, drilling two wells. The first, Riquah-2 was Processing Division. He was a dry hole with only shows of oil; the second, Jlayah-1, employed by Digicon Geophysical, recovered a maximum of 420 bopd on test from the Ratawi Houston, Texas from 1983 to 1985 Formation. and also held the position of Processing Manager with Tensor In order to establish an integrated sequence-stratigraphical Geophysical, Cairo, Egypt from 1986 framework for the prospective Lower to Middle Cretaceous to 1990. Peter received his BASc in interval, a quantitative biostratigraphical study was made. Geologic Engineering (Geophysics) Some 790 biostratigraphical analyses (10% core samples; from the University of British Columbia, Canada in 1983. 90% cuttings) from eleven wells were carried out by He is a member of the EAGE, SPE and SEG. His Robertson Research International Ltd. (micropaleontology) professional interests are seismic processing and image and Varol Research (nanno-fossils). The nanno-fossil data processing. were particularly important in providing accurate chronostratigraphical calibration, and this data has been used Anthony A. Sirtautas holds BSc and to constrain a preliminary “Time-Rock Synopsis”. MSc degrees from the Colorado School of Mines in Geophysics and KOC’s lithostratigraphical nomenclature proved to be has been an Applications Analyst basically sound and has been maintained as the basis for the with the Geophysical Applications present stratigraphical framework. However, the study Division of Saudi Aramco in revealed the existence of two substantial and hitherto Dhahran for the last 7 years. unsuspected hiatuses: one between the Ratawi and Zubair Anthony has had over 15 years formations, of Early Valanginian to Mid-Hauterivian age; experience in the and the other, representing the whole of the Early Albian, working with , Digicon within the Burgan Formation. This latter result, if it can be and Multiflow Computers. further substantiated by more exhaustive study in the onshore area, would neccessitate a redefinition of the Burgan Formation and the erection of a new formation to describe A New Look at the Middle-Lower the clastic sequence of Late Aptian age which was deposited before the Early Albian hiatus and after the Shu'aiba Cretaceous Stratigraphy, Offshore Kuwait Formation, and which has hitherto been included within the Lower Burgan Formation. Abdul Aziz Al-Fares Kuwait Oil Company Abdul Aziz Al-Fares graduated from Pete Jeans and Mark Bouman Kuwait University with a BSc degree Shell International Exploration and Production B.V. in Geology in 1992, and in the same year he joined Kuwait Oil Company In September 1995, a joint study was initiated between Shell as a Wellsite Geologist. In 1994 International Exploration & Production B.V. and Kuwait Abdul Aziz was assigned to work as Oil Company (KOC) whereby an integrated team of Shell a Geophysicist at KOC, and from and KOC geologists and geophysicists, based in The Hague November 1995 to December 1996 (The Netherlands), undertook to review the hydrocarbon he was a member of the KOC/Shell potential of offshore Kuwait, including Kuwait Bay and Joint Study Team. He is currently Bubiyan Island. working as a 3-D Seismic Interpreter.

Offshore exploration in Kuwait commenced in 1961 with Pete Jeans is currently a Regional the award of a 5,600 square kilometer offshore concession Business Advisor in Shell EP to Shell. Some 6,300 kilometers of 3-fold analogue seismic International Ventures’ New Business were acquired in 1961, and 3 wells were drilled in 1962-63. Development Group. Prior to this, The most encouraging results were obtained from the first he was Senior Geologist and then well drilled, Riquah-1, which tested at an initial rate of 720 Project Leader of the Kuwait Joint ° bopd of 38-40 API oil from Lower Cretaceous Ratawi Study Team. Pete graduated with a limestones. Hamuur-1 had minor oil and gas shows, whilst PhD in Geology from Birmingham a minor gas influx was noted in Zubeidi-1. All three wells University in 1973, and worked in were abandoned. In the same period, KOC also drilled their Oman, Jakarta, Houston, and Brunei first offshore exploration wells: Bubiyan-1 (which bottomed before returning to the Hague in 1989. His particular in Jurassic salt at 14,251 feet), Bahrah-5, and Failakah-1. In interest is prospect and play generation. 1981, KOC embarked upon a second offshore exploration

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Mark Bouman gained a MSc in Sargelu formations have approximately similar facies from Stratigraphy from the University of north to south. Whereas, the Lower Liassic petroleum system Utrecht, and joined Shell in 1982. of Alan, Mus and Adaiyah are composed mainly of Following assignments in Peru, evaporites in the north, to pseudo-oolitic and tight limestones London, and Cairo, he returned to the in the south. Hague in 1995 and was Senior Stratigrapher in the Kuwait Joint Mohammad Al-Gailani is currently Study Team. Mark is currently Managing Director of GeoDesign Course Director for Geosciences in Limited, a consultancy based in the Shell Learning and Development London specialising in databases of Centre, Noordwijkerhoud, in The Netherlands. His areas of the Middle East. He graduated from expertise include sequence stratigraphy, basin analysis, and Baghdad University in 1972 with a stratigraphical computing. BSc degree in Geology and worked briefly for the Iraqi National Oil Company in Baghdad. He won a Jurassic Petroleum System scholarship in 1973 for Post- Graduate studies in where he obtained in Southern Iraq first his MSc in 1974 from University of Aberdeen and then PhD and DIC in January 1979 from Imperial College, Mohammad Al-Gailani London. Mohammad worked as an independent consultant GeoDesign Limited on several projects both in the Middle East and the Parana Basin in South America where he worked for Pauli Petro in Most of the developed hydrocarbon reserves in Iraq lie Sao Paulo, Brazil. He has published several papers on the within the Tertiary and Lower Cretaceous petroleum diagenesis and reservoir characteristics at unconformities systems. However, in the past decade, deep drilling activities and on the exploration potential of Iraq. He has been an in the fields of North Rumaila and West Qurna have proven active member of the AAPG and a member of the PESGB. the existence of a Jurassic pay zone producing very light crude with high API, low sulfur accompanied by some sour gas. Sulfur versus API-Gravity Relationships The Jurassic petroleum system in southern Iraq comprises of Iraqi Crude Oils two major rich source rocks laid as part of two different depositional cycles. An early Bathonian-Liassic cycle Mohammad Al-Gailani depositing the Sargelu Formation and a Lower Kimeridgian GeoDesign Limited to Oxfordian cycle depositing the Naokelekan Formation. Michael D. Lewan and Thomas S. Ahlbrandt Both hydrocarbon source kitchens and reservoir seal US Geological Survey combinations existed within the Middle to the Upper Jurassic basin. This basin was developed over two tectonic regimes, It has long been recognized that sulfur content of genetically the Platform Flank of Mesopotamian Foredeep and the North related crude oils increases with decreasing API-gravity. Eastern Slope of the African-Arabian Platform. Plots of this relationship have been used as a typing tool to differentiate between high- and low-sulfur crude oils The distribution and the possible syntectonic deposition of irrespective of the maturity level at which they were the various Jurassic formations over growing structures has generated. Although more sophisticated typing methods created various lithofacies. These range from carbonate mud employing gas chromatography/mass-spectrometry accumulation to oolitic shoals, and lagoonal evaporatic to currently exist, sulfur and API-gravity data are more readily bedded anhydrite acting like source kitchens / reservoir trap available and allow for more global typing of crude oils as and seal capping facies favorable for hydrocarbon generation a first approximation. In this study, 330 oils from 34 fields and entrapment conditions. in Iraq were used to determine whether a genetic sulfur versus API-gravity relationship existed. Several fields with It is concluded that the best reservoir targets for the Jurassic Mesozoic and Cenozoic oils that have not been significantly petroleum system are the Upper Jurassic Najmah and Upper altered by water washing or biodegradation and that span a Liassic Mus formations. Both of these formations exhibits wide range of API gravities and sulfur contents gave a high- oolitic to pseudo-oolitic lithofacies with good porosities, sulfur genetic relationship. Cenozoic and Mesozoic crude covered by tight evaporites and underlain by good quality oils from Kuwait, Iran, Qatar, and Saudi Arabia also follow source rock kitchens. It is evident from the lithofacies this relationship, which suggests a common regional source description of the various Jurassic formations that the Upper rock for the Arabian Gulf basin. Sulfur/API-gravity Jurassic petroleum system of Najmah, Naokelekan and relationships of high-sulfur oils in Alberta, Nevada,

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California, Wyoming, Gulf Coast, and Venezuela indicate Geological Evaluation and Hydrocarbon that differences in the depositional conditions of their source rocks results in significant differences in the slopes and Potential of the Middle Jurassic intercepts of their sulfur/API-gravity relationships. Oils Araej Formation in Abu Dhabi, from the Smackover of the Gulf Coast and from the United Arab Emirates Mesozoic and Cenozoic of the Arabian Gulf basin have essentially the same relationship, which suggests that Abdulrahman S. Al-Habshi, Ahmed A. Taher, depositional conditions of their source rocks were similar. Mohamed M. Abd El-Sattar and Omar Suwaina Their similar relationships also have the highest intercepts Abu Dhabi National Oil Company (S = 6.8 to 7.0) and slopes (S/API = -0.151 to -0.148) of the regions studied. In addition to the high-sulfur relationship, The Middle Jurassic Araej Formation is an exploration target Paleozoic oils from the Akkas field in Iraq and those from in offshore Abu Dhabi. It was deposited on prevailing Saudi Arabia give a low-sulfur genetic relationship. This shallow to very shallow warm and clear water shelf distinctly different relationship indicates the existence of a conditions. Epeirogenic movements during the Middle Paleozoic petroleum system in Iraq, similar to that observed Jurassic period caused fluctuations in water depths and in Saudi Arabia. consequently produced a variety of limestone types represented by the alternations of lime-mudstones, Mohammad Al-Gailani (see abstract "Jurassic Petroleum wackestones and packestones/grainstones. Sedimentation System in Southern Iraq" on page 49 for biography and of the Araej Formation was controlled by several structural photograph) factors, the most important of which was the Qatar Arch which was subject to uplifting at the early Jurassic and Michael D. Lewan is Leader of the through the Araej time, particularly at the end of the Middle Hydrocarbon Processes Group for Jurassic (basal Diyab Unconformity and extensive erosion the Energy Resources Program of the of the Qatar Arch). US Geological Survey, where his research efforts for the last 7 years The regional electric log correlations coupled with have been on developing a lithofacies interpretation revealed the presence of seven quantitative understanding of acceptable lithostratigraphic units (two in the upper Araej petroleum expulsion and kinetics. Member and five in the lower Araej Member) for the Araej Prior to this, Michael spent 13 years Formation. The integration of lithofacies and seismic at the Amoco Production Co. modeling reveals that the high energy shelfal highstand Research Center, where he pioneered the development of grainstones having the highest porosities occur in northern, hydrous pyrolysis for simulating natural petroleum central and western offshore Abu Dhabi. generation. He also worked for three years as an exploration geologist for Shell Oil Co. in the Gulf Coast offshore. Good reservoir development is found in the shallow water Michael received his PhD from the University of Cincinnati shoal pellety and/or oolitic packestones/grainstones in and MSc from Michigan Technological University. offshore Abu Dhabi fields, where hydrocarbon accumulations have been discovered at depths ranging from 9,100 and 12,500 feet subsea in the Upper Araej (Unit 1), Thomas S. Ahlbrandt is the Project Uweinat and Lower Araej (Units 1 and 2). Contribution of Chief of the World Energy Project low-maturity oil from the Diyab Formation is likely and the and Coordinator for Region 2, the available geochemical analyses suggest that the predominant Middle East. He received a BA and a gas charge is derived from a source developed within the PhD in Geology at the University of pre-Diyab Mesozoic section. Wyoming. Thomas served on the Executive Committee of the American Abdulrahman S. Al-Habshi is Association of Petroleum Geologists currently Supervisor of the Review and on the US National Committee Geology Section with Abu Dhabi for the World Petroleum Congress. National Oil Company (ADNOC). From 1965 to 1988, he worked for Exxon, USGS, Amoco, He has 25 years of experience in Amerada, MRO and Associates and was partner in Petrostat geology of which six and a half years Consultants. Thomas rejoined the USGS in 1988 and has were with the French company held various energy positions in Reston, Virginia and in BRGM in Jeddah, Saudi Arabia, four Denver, Colorado. and a half years with the Petroleum Department in Abu Dhabi and 14

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years with ADNOC. Abdulrahman is Vice Chairman of the of several diagenetic features such as mechanical Society of Explorationists in the Emirates and a member of compaction and development of pressure solution, compact the SPE. He obtained his BSc in Geology from Baghdad cementation with silica, corrosion of quartz grains, University in 1971. dissolution of feldspar and rock fragments and development of oversize pores, replacement of detrital grains by Ahmed A. Taher is a Senior authigenic carbonates, alteration of feldspar into clays. For Geologist with the Abu Dhabi reliable interpretation of provenance, the diagenetic history National Oil Company (ADNOC) of the rock must be considered. Based on conventional types since 1982 and has worked as an of point counting, quartzarenite is dominated by mature Explorationist for the ADNOC quartzose grains. However, when the dissolved grains are concession areas. He received his considered a different provenance is indicated. BSc in Geology from United Arab Emirates University. Ahmed is a Omar A. Al-Harbi is currently member of the Society of Associate Professor of the Natural Explorationists in the Emirates. He Resources and Environment is particularly interested in the statistical modeling of source Research Institute at King Abdulaziz rocks and its maturation regime. City for Science and Technology. Omar is a member of the AAPG and Mohamed M. Abd El-Sattar is a the Saudi Arabian Society for Earth Senior Exploration Geologist with Science. Abu Dhabi National Oil Company. He has 21 years of petroleum and exploration experience in the Middle East, of which 11 years were with Gulf of Suez Petroleum Co., Egypt. Reservoir Description: Use of Core Data Mohamed holds BSc and MSc to Identify Flow Units for a degrees in Geology from Ain Shams Clastic North Sea Reservoir University, Egypt. He is a member of many professional societies and has published several O.B. Al-Mahtot and W.E. Mason papers on structural geology and basin evaluation. Robert Gordon University, Aberdeen, UK

Omar Suwaina is currently Senior An effective and sufficient description and characterization Seismic Interpreter within the of the reservoir are ultimately essential to successful Onshore Geophysics Group in Abu reservoir engineering management. The integration of Dhabi National Oil Company sufficient core analysis data is the primary target of reservoir (ADNOC), Abu Dhabi, UAE. He has description to permit identification of zones (Flow Units) worked in the processing and with similar fluid-flow characteristics. The identification of interpretation of 2-D and 3-D seismic flow units is the aim of integrated core analysis program. data of ADNOC surveys. Omar is a The flow units technique is a method of characterizing a member of the Society of reservoir, and the route to flow unit and reservoir description Explorationists in the Emirates and is dependent on the core data available. SEG. He obtained his BSc in Geological Engineering in 1990 from the Colorado School of Mines. This paper presents a practical application of the flow units technique to a clastic North Sea reservoir using a statistical analysis for flow zone indicator (FZI) to differentiate flow Diagenetic Evolution and its Effects on units. All laboratory work was conducted using one-inch Provenance Interpretation of Devonian long cores. Core analysis porosity and permeability data from 410 core plugs was used to work out the porosity- Tawil Formation, Central Saudi Arabia permeability relationship using the flow units technique. After flow unit characterization, six flow unit groups have Omar A. Al-Harbi been selected, and samples of each individual flow unit were King Abdulaziz City for Science and Technology selected for mercury injection analysis using injection pressures up to 50,000 pounds/square inch. Finally the pore Diagenesis of quartzarenite of the Tawil Formation was size distribution and mean flow radius were calculated. In studied to characterize its effects in provenance studies. The this paper the applicability of this technique is discussed to main framework of this sandstone is quartz, feldspar and examine how an improved reservoir description can be rock fragments. The petrographic study reveals the presence achieved for a specific reservoir.

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This paper describes a new attempt to apply this technique Application of Multi-Seismic Attributes to a North Sea reservoir. The technique is more complex than either the depositional or layer model, but is also the in Estimating Reservoir Properties most realistic because it takes account of a wide variety of geological and petrophysical characteristics present. The Maher I. Al-Marhoon properties used to derive flow units in this reservoir were Saudi Aramco the core-porosity and permeability measurements for small, medium and large pore-throat radii. The general porosity- Seismic attributes can be used in seismic interpretation. As permeability cross-plot shows a large scatter, indicating poor seismic data quality improves, interpretation of seismic overall correlation between porosity and permeability. attributes becomes more reliable. Seismic attributes reveal However by using the flow units technique a reasonable information that often cannot be detected in conventional relationship between porosity and permeability can be shown seismic displays. The attributes can be used for both to exist for each individual flow unit. quantitative and qualitative interpretation of any zone of interest. The flow unit technique provides a comprehensive reservoir description. Six flow units are defined; three of these exhibit The main goal of this study is to estimate porosity, water good-to-excellent reservoir quality, one is good reservoir saturation, and volume of silt using several seismic attributes quality and two are poor reservoir quality. It can be said and then arrive at one conclusion based on the quantitative that this technique has been applied successfully to this and the qualitative analyses. particular North Sea reservoir. In the quantitative analysis, nine seismic attributes are used O.B. Al-Mahtot graduated from Al- to estimate the reservoir properties mentioned above. These Fateh University, Tripoli, Libya with attributes are calculated and averaged over the zone of a degree in Petroleum Engineering interest, from Base Khuff to the pre-Unayzah Unconformity, in 1987. He worked as Science compared to the log-derived reservoir properties from 19 Teacher in the Ministry of Education wells. Multi-variant regression is used to approximate a between 1987 and 1988, as linear transformation between seismic attributes and Production Engineer with Oxy Oil reservoir properties. Then the transformation is applied to Company between 1988 and 1980, the whole seismic data. then joined Nasar University as Assistant Teacher in Petroleum In the qualitative analysis, spectral attributes are studied in Engineering in 1990. He received his MSc in Offshore addition to the nine seismic attributes discussed in the Engineering from Robert Gordon University in 1994. He is quantitative analysis. Attributes are related to the reservoir currently a PhD candidate at Robert Gordon University and properties qualitatively. Both the quantitative and the his research focuses on the effect of porosity type, overburden qualitative interpretation are in agreement. pressure and experimental conditions on electrical properties of sandstone and carbonate rocks. I preserved two wells for validation purposes. The estimated reservoir properties of these two wells using a multi-seismic W.E. Mason graduated from attributes approach are in agreement with the well driven Imperial College, London with a reservoir properties. The multi-seismic attributes driven degree in Chemical Engineering. He reservoir properties method was compared to the single- received his PhD from Imperial attribute method and to a method utilizing simple kriging College in 1966. He worked in of well information. government research on problems of mining safety. He joined the Maher I. Al-Marhoon has a BSc in University of Malaya as Lecturer in Geophysics (1990) and MSc in Chemical Engineering in 1969 and Geology (1997) from King Fahd transferred to the University of University of Petroleum and Singapore in 1976 and was appointed Head of the Minerals, Dhahran, Saudi Arabia. Department of Chemical Engineering in 1979. He joined Maher is currently with the the Robert Gordon University in 1983. His current research Geophysical Technology Division of interests are in and thermodynamics. Saudi Aramco. He is a member of the SEG and Dhahran Geological Society.

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A Regional Sedimentological Study Zuwena Al-Rawahi received her MSc in Clastic Sedimentology from of the Lower Cretaceous Shu'aiba McMaster University, Hamilton, Formation in Oman Ontario, Canada in 1993. Zuwena is currently working on her PhD Zuwena Al-Rawahi and Neil A. Harbury project on the Sedimentology of the Birkbeck College and University College London Upper Kahmah Group in Oman at Birkbeck College, University of The Aptian Shu'aiba Formation (80-300 meters thick) crops London. out extensively in Oman and forms a major hydrocarbon reservoir in the subsurface throughout northern Arabia. In the studied area, Shu'aiba sediments represent deposition Neil A. Harbury received his on a broad shallow ramp or open shelf platform and comprise undergraduate degree from Imperial predominantly of low energy open marine subtidal carbonate College in 1982 and completed his muds characterised by an abundance of Requieniid “clinger” PhD in Geology from University rudists and algae. College, London in 1986. Neil started lecturing at Birkbeck College A study of both outcrop and the subsurface data provides in 1985 and has been the Course an excellent opportunity to examine the Shu'aiba regionally. Director of the MSc program in Outcrops in the Huqf region of central eastern Oman, and Sedimentology since 1989. His in the salt cored structures of Jebel Madar and Salakh as research interests include well as selected outcrops in the Oman Mountains have been sedimentation in areas of active tectonics and he is currently studied. These are compared with subsurface data. conducting research projects in the Middle East and Mediterranean (Oman, Yemen, Italy, Bulgaria) and In northern Oman, lithofacies identified range from southeast Asia (Sumatra, northeast Borneo). calcareous shales of the inner neritic zone to stromatoporoid- algae-rudist facies representing shallow marine shelf deposition, and skeletal-rich redeposited facies of the Application of Potential Field Data platform edge. in Oman The carbonate sediments are characterised by bioclastic wackestones to packstones forming small-scale shallowing- Salim Y.S. Al-Rawahy upward cycles with syndepositional hardgrounds and have Petroleum Development Oman an abundance of lime mud, peloids and coated grains. Sedimentation was predominantly in a subtidal environment In the past, potential field measurements, i.e. magnetic and with localised grainstones representing storm deposits. gravity data, were used in Oman, as elsewhere in the oil Facies are generally discontinuous and a complex industry, solely to map the extent of sedimentary basins and interfingering of facies over short lateral distances is major fault zones. Such geological features perturb the commonly observed. Earth's gravity and magnetic fields and may cause anomalies of a few tens of milligals and a few tens of nanoteslas, In contrast, the Shu'aiba in east-central Oman is thinner and respectively. For a given set of geological conditions, the comprises shallow marine subtidal and intertidal carbonates limitation in how small features could be resolved was which are cyclic with ferruginous hardgrounds. Several imposed by the precision of the measurement instruments incursions of fine-grained marls suggest a terrigenous and the resolution. In recent years, however, the advances source. This is in agreement with the regional in the potential field measurement instruments, accuracy in paleogeography and implies that sediments in this area are the geographical positioning and computers have allowed more proximal from those to the north. more accurate, and higher precision and resolution data to be recorded and readily analysed. These have paved the Although these carbonates were deposited in different way to the application of magnetic and gravity techniques paleogeographic areas, a broad facies correlation of the in detecting intra-sedimentary features that cause only a Shu'aiba Formation will be attempted utilising the excellent fraction of a milligal or of a nanotesla. Compared with biostratigraphic zones previously established for this seismic, these techniques are cheaper and, due to the fact stratigraphic unit. that they are measuring different rock properties from those measured by seismic, can provide extra subsurface information.

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In Oman, Petroleum Development of Oman has carried out In order for misties caused by FDS to be eliminated when a number of high resolution gravity and aeromagnetic blocks are merged during processing, we propose a solution surveys to validate or supplement seismic data. which must be implemented at the surveying phase. We Aeromagnetic data have been used to complement the simply recommend that an additional leeway (on top of the seismic interpretation in the areas of poor seismic data proposed acquisition area) be surveyed. The selection of quality and/or lack of acoustic impedance contrast between this leeway is entirely determined by the planned future the successive formations of interest. Gravity data have surveys. Stated differently, when the seismic data of a block been used to constrain the seismic interpretation over salt is acquired at a given time, a small part of the block adjacent diapirs where seismic imaging is poor. Here we present to it (the block to be acquired next) must be simultaneously some examples of these data including acquisition, surveyed in order for the FDS to be the same in the overlap processing and their analysis. zone, thus eliminating the artifact of misties.

Salim Y.S. Al-Rawahy received his Khalid Al-Rufaii holds a BSc in BSc in Geophysics from Liverpool Geophysics from King Fahd University in 1990, and MSc and University of Petroleum and PhD degrees in Geophysics from the Minerals, Saudi Arabia in 1988, a University of Durham in 1991 and MSc in Geophysics from Colorado 1995, respectively. Salim is currently School of Mines in 1992. Khalid working with Petroleum Development joined Saudi Aramco in early 1993 Oman in a team that is responsible for working in 3-D processing. His carrying out VSP interpretation and interests are simultaneous solutions quantitative seismic interpretation. to velocity and statics, and relative He is also responsible for non-seismic data and their amplitude processing. interpretations. Such data include gravity and aeromagnetic measurements. Stephen Bremkamp received his BSc in Geophysics from Colorado School of Mines. He worked with Western Optimal Merging of Large 3-D Geophysical in Denver, Colorado Seismic Surveys and Midland Texas. Stephen joined the geophysical processing division of Saudi Aramco in 1990. Khalid Al-Rufaii, Stephen Bremkamp and Ramzy Al-Zayer Saudi Aramco Ramzy Al-Zayer has been working in Processing large 3-D seismic surveys can be challenging. 3-D seismic processing since 1994. Due to acquisition limitations and/or software and computer Before that he was working on resources, large surveys are usually subdivided into rotational assignments in the multiblocks prior to processing. Each block undergoes a Exploration Organization. Ramzy separate processing flow up until a certain stage, usually joined Saudi Aramco in 1988 after the DMO stack, before different blocks are merged into a receiving his BSc in Geophysics from single giant block. Prior to merging, the different blocks King Fahd University of Petroleum would typically have identical processing flows and and Minerals. He is currently parameters. In our case, each individual block would span working on his MSc in Mathematics. an area of about 200 square kilometers. Merging separately- His interests are optimization and signal processing. processed blocks does not necessarily yield a smooth product; misties might arise at block boundaries due to improper merging. Oil Families of Oman Here, we analyze the mistie problem by identifying the various factors leading to misties. Of all the factors Nashwa Al-Ruwehy and Neil L. Frewin contributing to misties, we find that the Floating Datum Petroleum Development Oman Statics (FDS) is of utmost importance. If FDS in the overlap zone between two blocks is different, then the statics and In the identification of new prospectivity in mature areas, velocities will also be different for each dataset (in that knowledge of oil families and their oil source rock overlap zone), thus giving rise to misties. correlation is the key element. This is particularly important in Oman as the potential source rocks range from Precambrian to Cretaceous in age and all have probably contributed to the producible hydrocarbons. 54

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Four end member oil families have been identified within Neil L. Frewin is currently Senior Oman: Natih, Tuwaiq, 'Q' and Huqf. These end members Petroleum Geochemist for Petroleum have been identified by their detailed geochemical signatures Development Oman (PDO). Prior to using biomarkers, carbon isotopes, and migration distance being posted to PDO in 1997, he indicators. These tools have given us hard data which worked for Shell International in The constrains our models of the petroleum system of Oman. Netherlands as a Research Geochemist. He holds a BSc in The Natih sourced oils are characterised by having a Geology from the University of Wales relatively high C27 sterane abundance, and greater than 35% and a PhD in Geology/Geochemistry C28 sterane relative to sterane abundance, ∂13C measured from the University of London. Neil at -27‰. Pure end members have been identified in the spent a post-doctoral year researching biomarker Natih and Shibkah fields. technologies at Delft University, The Netherlands.

The Tuwaiq reservoired oils are recognised by having equal ∂13 amounts of C28 and C29 total sterane abundance and C A Practical Method of Estimating measured at -26.5‰. Pure end members have been identified in Mazhour-1 and Lekhwair-B fields. Permeability Distribution in Tight Gas Reservoirs of Saudi Arabia The 'Q' sourced oils are recognised by having a high C27 sterane abundance of greater than 50% in total relative to Ghiyath Al-Sabeq other steranes and ∂13C measured at -30.4‰. Additionally, Saudi Aramco the 'Q' oils have a distinctive and as yet unidentified compound which is not found in other oils. This peak has Permeability is one of the most important reservoir yet to be identified in a known source rock. Pure end parameters that petroleum engineers use. In the oil and gas members have been identified in Haima and Natih reservoirs industry, it is used as part of the process to identify well in Saih Rawl and Bahja fields. completions, to determine whether a well should be completed and brought on-line, and to help to choose optimal The Huqf source rocks produce Huqf typed oils which are reservoir management and development parameters such as recognised by having high abundances of C29 steranes, production rate, perforation design and drainage points. (greater than 50%) relative to other steranes and ∂13C Several permeability measurement and estimation measured at -37.1‰. Pure end members have been techniques are used in the oil and gas industry such as identified in Dhulaima, Jebel Madar and Jazal. Within this wireline-log measurents (including RFT method), core broad group, the Huqf is comprised of three end members analysis, well testing, and empirical correlations. It is the which can be distinguished in south Oman using triaromatic special interrelationship between these techniques and the steroids: (a) the Precambrian Buah & Shuram; (b) the procedure used to arrive at a permeability estimate that Cambrian Athel; and (c) the Cambrian "U". makes this method a practical one. This method: (1) uses modified Kozeny and Carman empirical correlation (that Both Huqf and 'Q' oils contain common compounds known uses core data) to classify permeability based on the as 'X' peaks (isomers of methyl and dimethyl alkanes. identification of hydraulic units (facies). This also requires basic classical statistical techniques such as histograms and The undisputed classification of Oman's hydrocarbons is frequency diagrams; (2) well test permability data is related hindered by the extensive mixing of oils during migration to core permeability data by a fitted transform(s) using from their respective source rocks along sometimes long regression analysis; and (3) the porosity distribution distance pathways. Furthermore, until the actual source of available from cores/logs/lithology (in the form of net the 'Q' is penetrated, the search for the enigmatic 'Q' source porosity-thickness) can now be used along with the available will continue. transform(s) (well test permeability thickness versus core permeability thickness) to distribute well test permeability. Nashwa Al-Ruwehy has been employed by Petroleum Development Ghiyath Al-Sabeq is a Petroleum Oman since 1981. Nashwa holds a Engineering Specialist in Reservoir BSc Sciences degree from Management at Saudi Aramco. His Portsmouth in 1977 and obtained an previous position was as a Specialist MSc in Palynology, from Sheffield in the Division University in 1990. Nashwa is at Saudi Aramco where he worked on currently employed as a Geochemist different aspects of reservoir in the Regional Studies Team. simulation modeling studies covering model construction, history

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matching, and performance predictions of various fields in Salem H. Al-Sabea received his BSc Saudi Arabia. Ghiyath holds a BSc degree in Engineering degree in Geology from Kuwait Sciences with honors from King Fahd University of University in 1990 and joined Kuwait Petroleum & Minerals, and an MSc degree in Chemical Oil Company in December 1991 as Engineering from Oklahoma State University. a Well-Site Geologist. Salem has worked as a Petrophysicist since 1994. Log Data Normalization, the Greater Burgan Field, Kuwait

Mariam Al-Saied, Salem H. Al-Sabea Kamal E. Osman is currently a and Kamal E. Osman Senior Petrophysicist with Kuwait Kuwait Oil Company Oil Company. He joined Chevron Overseas in 1980 and has been a Over 50 years, 768 wells were drilled in the Greater Burgan Formation Evaluation Specialist with field. During this period, different vendors and several since 1989. He received his BSc in vintages of logging tools were used to acquire openhole log Geology from Khartoum University data. Significant systematic variation exists between in 1979. Kamal is a member of the measurements made by different generations of logging tools SPWLA and SPE. from the same vendor and between tools from different vendors. These variations lead to major errors and inconsistencies in petrophysical evaluation results. Field- wide data normalization was necessary to reduce these errors The Impact of Reservoir Characterisation and to establish consistency in full-field petrophysical on Field Management: Minagish Oolite evaluation. We normalized gamma ray, density, sonic, and neutron data to obtain consistent results. Reservoir, Umm Gudair Field, Kuwait

Cumulative frequency histograms were used for Nawaf S. Al-Salem, Ram S. Gaur normalization. Modern wireline log (1990’s vintage) data Kuwait Oil Company were used to establish the normalization standard. The and Clive D. Bishop Mauddud carbonate formation, Wara and Burgan shale zones BP Exploration, Kuwait were selected as reference points. The cumulative frequency histograms for each zone were examined to determine The Umm Gudair field is located on the southwest flank of common cumulative frequency percentile and log value pairs the Kuwait Arch, adjacent to the Burgan field. Oil is that were consistent in the reference wells. The selected reservoired at several levels within the Jurassic and reference pairs were then compared with corresponding Cretaceous intervals but initial development has focused on values obtained from the other wells to determine the the Lower Cretaceous Minagish Oolite reservoir. The field magnitude of change required for normalization. extends southwards into the Kuwait/Saudi Arabia Partitioned Neutral Zone, where it is referred to as the South Umm About 60% of the wells required significant normalization. Gudair field. The discovery well was drilled in 1962 and Data normalization resulted in average shifts of 3.0 MS for initial development drilling continued through to 1967. sonic data, 5.0 PU for neutron, 0.15 g/cm3 for density and Drilling resumed in the 1980s, with a major expansion of 7.0 API for gamma ray. activity in 1993 which is continuing at present. 120 wells have been drilled to date and approximately 400 million Mariam Al-Saied received her BSc barrels of oil have been produced. degree in Geology from Kuwait University in 1982. She joined The recent renewal of development drilling has provided Kuwait Oil Company in February the opportunity for collection of new core, wireline, pressure 1995 as a Petro-physicist/Geologist. and fluid data on which to base an updated description of the Minagish Oolite reservoir. The 450-foot thick Berriasian-Valanginian interval was deposited on a homoclinal carbonate ramp. Three systems tracts are defined, representing 3rd-order sea level cyclicity, each comprising a series of 4th-order parasequences. The dominant rock types are high permeability inner-mid ramp skeletal packstones and grainstones plus inner ramp oolitic

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sandsheets. Flooding events, associated with the 3rd-and Bridging Gaps Between Surface Seismic Data 4th-order cyclicity resulted in deposition of thin mid-outer and VSP Data for the ramp bioturbated peloidal packstones and wackestones, which form extensive low permeability units. Increased Improvement of Subsurface Imaging frequency of sea level fluctuations and relative deepening towards the top of the reservoir results in an upwards increase Riaz Alá’i in the proportion and continuity of these deeper water facies. Delft University of Technology, The Netherlands

Integration of Repeat Formation Test pressure data with the Vertical Seismic Profiling (VSP) has proven amongst many static description has shown that the fine-grained units other geophysical techniques, to be extremely useful to associated with flooding events have the potential to impact obtain a more detailed seismic view on subsurface imaging fluid flow through the reservoir. Pressure barriers up to by investigating the characteristics of imaged structures from 700 psi are observed and an upper unit has been defined nearby. For optimal interpretation and identification of the which is isolated from the main part of the reservoir. This structures at a reservoir, it is fundamental to tie the VSP new understanding has to be reflected in modifications to measurements with the unmigrated surface seismic data the field development plan. (time-axis in common) as well as with the migrated seismic data (depth-axis in common). Due to the acquisition Water coning is a key issue for reservoir management. The geometry for the VSP measurements it may be that the data reservoir has bottom water across its entire area and the high is not recorded at all the depths one is interested in (e.g. the Kv/Kh ratio, within the main part of each parasequence, target level). In this paper some field data examples will be has been enhanced in the near wellbore area by repeated presented in which the missing data in VSP data at particular acid stimulation. Identification of the thin low permeability depth levels can be interpolated by “virtual” VSP data which layers and placement of Injectrol and cement plugs at these is determined from the unmigrated surface seismic data and levels have proved successful in holding back water cones, an estimated model of the subsurface. The use of “virtual” reducing water cuts from 50% to 2% over sustainable VSP data can be used for improving the quality of real VSP periods. data together with its use in the prediction ahead of the drillbit. An additional advantage of this method is that Nawaf S. Al-Salem graduated in Amplitude Versus Offset (AVO) behavior of structures at Geology from Kuwait University in reservoirs intersecting the well can be investigated by 1996. He has worked with Kuwait Oil enlarging the offsets of the source with respect to the well. Company for 2 years with experience Summarizing, some field data examples emphasize the in reservoir studies and wellsite optimal illumination and subsurface imaging by bridging operations. gaps between surface seismic data and VSP data. Moreover, the method allows optimal design of VSP acquisition geometries to accurately define attributes which could be used to estimate reservoir properties and thus defining the reflectivity as one progresses away from the well.

Ram S. Gaur (see abstract "The Heavy Oil / Tar Mat in Riaz Alá’i received his MSc degree Minagish Field, Kuwait: Detection, Characterization and in 1991 from Delft University of Impacts on Reservoir Performance" on page 42 for Technology in Electrical Engineering biography and photograph ) specializing in Control Engineering. In 1992 he started his PhD research Clive D. Bishop has 20 years at the Delft University of Technology, experience as a Geologist and has Centre for Technical Geoscience, worked as a Senior Geologist with BP Department of Applied Physics, Exploration since 1981. He is where he was a staff member of the currently seconded to the Kuwait Oil Internationally sponsored DELPHI Company, working in the Umm (DELft PHilosophy on Inversion) Consortium at the Gudair field team and assisting with Laboratory of Seismics and Acoustics. Riaz received his PhD the development of Kuwaiti degree in 1997 and towards the end of 1997 he joined the professional staff. Clive graduated Atlantic Richfield Company (ARCO) in Plano, Texas, USA. from the University of Wales in 1977 He is affiliated with the SEG and EAEG. His areas of and has worked in the North Sea, Egypt and Australia. Prior professional interest include wave theory and VSP to moving to Kuwait he also worked on a wide range of processing. reservoir characterisation projects at BP's research centre in the UK.

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Geostatistical Integration of 3-D Seismic well control, portrayed the east flank as a simple monocline dipping gently towards the east; the line of injector wells with Gravity and Wellbore Data to Identify are situated on this monocline just above the oil-water and Estimate Additional Reserves contact and thus provided no clue to the secondary structural in the Ghawar Field, Saudi Arabia high immediately to the east.

David W. Alexander David W. Alexander is currently a Saudi Aramco Senior Geophysicist in the Southern and Robert W. Jeffrey Area Reservoir Geology Division of Forcenergy Saudi Aramco, Dhahran, Saudi Arabia. He has 20 years of A previously identified structural closure - satellite to Saudi exploration and reservoir Arabia's Ghawar field - has been delineated using a development experience in both geostatistical integration of 3-D seismic, wellbore and geophysics and geology and has gravity data. Time and initial depth mapping of Ghawar's worked for Phillips Petroleum and main reservoir reflection (Arab-D), over the central part of Tenneco Oil Co. before joining the field's eastern flank, reveals an anomalous structural nose Aramco in 1990. David is an active member of the SEG plunging to the east, normal to the overall Ghawar structural and AAPG and a Certified Petroleum Geologist as well as trend. Conversion of the time structure to depth was a member of the EAGE and the Dhahran Geological Society. subsequently redone by applying revised depth conversion He holds BSc (1976) and MSc (1978) degrees in Geology velocities derived using a bivariate geostatistical approach from Brigham Young University. in which gravity data was used as a guide variable in estimating velocities away from well control. Residual Robert W. Jeffrey is a Geophysicist with Forcenergy, Alaska. gravity maps covering this area exhibit a strong visual Prior to joining Forcenergy, Robert worked as a Research correlation (and a statistical correlation of 0.76) with depth Geophysicist with Saudi Aramco, and prior to that, with conversion velocities calculated using well control. This Unocal. Robert attended the University of Washington and updated depth map shows significant closure in the satellite the University of British Columbia (Geological and structure and points to what could be a considerable amount Geophysical Sciences). He is a member of the AAPG, EAGE of Arab-D reservoir above the local oil-water contact. This and SEG. structure, as well as the presence of oil within the prospective area, have been subsequently confirmed by a well drilled on its south flank. Mechanism of Mid-Clysmic Event and its Having demonstrated the existence of the closure and the Effect on the Pre- and Post-Miocene presence of hydrocarbons, an assessment of the reserve Structure of Ras Budran Field, potential within the prospective area required an estimate Gulf of Suez, Egypt of the Arab-D pay-thickness above the local oil-water contact. Here again geostatistics proved an invaluable tool Ramadan Ali and Ali Mahmoud Khairy for integrating seismically derived reservoir porosity- Suez Oil Company thickness with porosity-thickness measured in wells. Top Arab-D seismic amplitudes were used as a guide variable The structural configuration of Ras Budran field which lies in a cokriging program which not only provided a reliable in the northeastern offshore side of the Gulf of Suez is Arab-D porosity-thickness prediction but also yielded the beyond controversy, considered as a complex pre-Miocene relative uncertainty in porosity-thickness. model.

Results from the geostatistically derived Arab-D structure Oil is produced from a "northeast" dipping Cretaceous and and porosity-thickness maps were combined to arrive at the Paleozoic Nubian sandstone reservoirs which are delimited reservoir porosity volume within the prospective area and to the east and to the west by a set of non-clysmic "northeast- above the oil-water contact. A volumetric calculation, which southwest" cross Gulf faults, most likely contemporaneous accounts for vertical as well as lateral variability in porosity, with the Gulf of Aqaba, and transferred the older set of shows this structure to contain a significant amount of net antithetic and synthetic gravity faults across, these pore volume. "northeast-southwest" trending boundaries, structurally shaped Ras Budran field into parallel segments. 3-D seismic supported by residual gravity, geostatistically integrated with standard borehole reservoir data, offers a The intensive phase of mid-clysmic tectonism during the more accurate interpretation of the east flank of Ghawar. Intra-Rudeis time produced uneven topography governing Previous structural and reservoir interpretations, using only the successive deposition of the overlying sediments and was responsible for the field present day structure anomaly.

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From the tectonic point of view, the Lower Miocene SUCO. Ramadan has also worked structural new model is very tempting to explain to what as Field Geophysicist with Western extent the structural set up controls the pre-Miocene trap Arabian Geophysical Company, a within the field and helps solving many geologic and Mud Logger with Geoservices reservoir uncertainties. International S.A., and as a Production Geologist with Deminex The Nukhul and Rudeis formations are of prime interest in Egypt. He received his BSc in the study area where the thickness distribution of these Geology from Al Azhar University in formations is widely differentiated and varies throughout 1980. the field due to the variation in rates of tectonic subsidence and uplifting during the Miocene times. However, this paper Ali Mahmoud Khairy is currently is an attempt to present the tectonic framework and its Development Geology Department relationship to Intra-Rudeis Event which in essence played Head with Suez Oil Company, Egypt. an effective role on the field remodeling. He has more than 18 years experience in the oil business and has Ramadan Ali is currently Head of Development Geology published papers in Development and with Suez Oil Company (SUCO), Egypt. He started as a Production Geology. Ali received his Well Site Geologist and Mud Logger and a Subsurface and BSc in Geology from Ain Shams Development Geologist with the Development Team of University, Cairo in 1979.

GEO’98: Short Course No. 2

Fractured Reservoirs Characterization and Modeling 18-19 April, 1998

Content: The lecture series integrates subjects from geology, geophysics, reservoir engineering and laboratory testing. The lecturers will define and illustrate how fractures may be used to build a comprehensive fracture network. The upgrading of such a model for reservoir simulation purposes and the description of a dual porosity simulator will be described. Participants will have the opportunity to gain a sound background on all the specific features of fractured reservoirs and to consequently be more able to limit the risk when managing them.

Topics include: specific features of a fractured reservoir, fracture families, fracture attributes, fracture characterization, seismic and fractures, modeling of fracture networks, numerical simulation, specific problems in fractured reservoir simulation among others.

Instructors are Research Scientists from the Institut Français du Pétrole: Bernard Bourbiaus, Marie- Christine Cacas, Jean-Marc Daniel, Francis Faure, Laurence Nicoletis and Jean-Claude Sabathier.

For more information please contact: Mr. Eric Gross IFP Arabian Gulf P.O.Box 3282 Manama, Bahrain Tel: (973) 214-778; Fax: (973) 217-908; e-mail: [email protected]

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Sedimentology, Diagenesis and Charge west flank. Modelling suggest this later charge to migrate mainly to the east into Haima structures along the western History of the Haima Deep Gas margin of the Ghaba Salt Basin. Gas expelled from source Reservoirs in North Oman: An Integrated rocks in the Fahud Basin charged structures across the Fahud Approach to Play Evaluation basin and reached the Makarem High (80 Ma - present day).

Joachim E. Amthor, Jos J.M. Terken Due to down-building of salt in the Ghaba Salt Basin gas Petroleum Development Oman charge from the western flank never reached structures and Marietta Vroon-ten Hove located near the eastern margin of the Ghaba Salt Basin. Shell International E&P Lack of ‘recent’ west flank charge, together with an adverse timing between structuration and early charge from the salt Exploration in the Ghaba Salt Basin of North Oman found basin provide each similar Haima structure in the Central substantial gas and condensate in sandstones of the Barik Ghaba Salt Basin with a charge risk. Sandstone Member (Andam Formation, Cambro-Ordovician Haima Supergroup) at depths between 4,200 and 5,200 These results of the interdisciplinary studies were translated meters. The observed play variations and uncertainties into better risks constraints for prospect ranking, reservoir highlighted the need for a interdisciplinary approach to the evaluation and calculation of reserves volumes. evaluation of this play. Joachim E. Amthor received a PhD A number of critical success factors were identified in a series in Geology from City University of of interdisciplinary studies: (1) The depositional environment New York Graduate School in 1990. determines the net sand content of the Andam Formation After two years as a Post-Doctoral sandstones. Fluvial/tidal reservoir sands grade towards the Fellow at McGill University in north into non-reservoir (marginal) marine heteroliths. (2) Montreal he joined Shell Research in The main diagenetic controls on reservoir quality distribution The Netherlands in 1992 as a are depth and the timing of liquid hydrocarbon charge. Early Research Geologist. In 1996 cementation by dolomite and depth-related compaction and Joachim was posted to Petroleum cementation (mainly by quartz) reduce porosity by 0.5% per Development Oman where he is 100 meters, whereas processes related to liquid hydrocarbon currently working as a Geologist in the exploration unit. charge improve or preserve porosity. The main diagenetic His work involves mainly reservoir-quality prediction in both factors were translated into an empirical function for clastic and carbonate rocks, with emphasis on how reservoir quality prediction. (3) Two different source rocks diagenetic processes affect hydrocarbon reservoirs on both have sourced most of the movable oils, condensates and gases the exploration and production scales. in the Haima in the Ghaba Salt Basin. Both source rocks are linked to areas of salt deposition and are thought to be located Jos J.M. Terken joined Shell in 1982 within and at the top of the Ara Salt. (4) The timing of the and has worked in exploration in The initial oil charge into the reservoir relative to the diagenetic Netherlands, Brunei, New Zealand and burial history is also a critical factor. Basin modeling and Indonesia. Since 1993 he has indicates three periods of hydrocarbon generation, during been with Petroleum Development Haima (Andam-Safiq) deposition (520-375 million years ago Oman as a Senior Review Geologist (Ma)), during Akhdar-Kahmah deposition (270-100 Ma) and and Basin Modeller in the regional during Aruma/Tertiary deposition (80-0 Ma). In the Fahud studies team. He received his MSc in Salt Basin, Early Ordovician/Silurian oil charge from the Geology and Sedimentology from the Ghaba Salt Basin was converted to bitumen through University of Utrecht in 1982. biodegradation either immediately after emplacement as a result of the shallow depth of the reservoir, or upon Marietta Vroon-ten Hove joined Carboniferous uplift. The resulting pore-filling bitumen has Shell International E&P in 1989 after downgraded the reservoir quality in older structures in this receiving her MSc in Geology from area. In the Ghaba Salt Basin, Barik reservoirs were charged the University of Utrecht. After her during Akhdar-Kahmah deposition (270-100 Ma). The first assignment as Seismo- greater burial depth (>3,000 meters) of the Barik reservoirs stratigrapher in Shell Research, she prior to charge resulted in significant pre-charge compaction was transferred to Shell Madagascar and porosity reduction by quartz cements, it safeguarded as Team Geologist. In 1994, Marietta the oil from biodegradation. (5) Gas charge and evolution joined Petroleum Development of migration pathways: gas was generated in the Ghaba Salt Oman to study the deep gas Basin as early as 510-375 Ma from Huqf source rocks and reservoirs as Sedimentologist. Currently, she is working as during Sahtan/Kahmah deposition from source rocks on the Seismic Interpreter for Shell’s Research and Technical Services Division in Rijswijk, The Netherlands.

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The Athel Play in Oman: efficiently expelled from the source rock and can remain intimately associated with the immobile source material. Controls on Reservoir Quality The calculation of bulk densities for the petrophysical evaluation of downhole porosity can therefore be hindered Joachim E. Amthor, Tom Faulkner, by the presence of hydrocarbons in as yet undefined phases. Neil L. Frewin, Jean-Louis Alixant Petroleum Development Oman During burial, the silicilyte most likely did not undergo the Albert Matter and Karl Ramseyer same dissolution/reprecipitation processes that characterize University of Bern Monterey Formation siliceous rocks, and which cause orders of magnitude reduction in porosity (up to 30% during opal- The intrasalt Athel silicilyte is a unique source and reservoir A to opal-CT transition alone). The early precipitation of a rock found in the South Oman Salt Basin, where slabs of stable silica phase helped to preserve some of the high Athel silicilyte are entrapped in salt at 4 to 5 kilometer depth. primary porosity. Most porosity loss after formation of the Discovered in the early 1990's, the play is characterized by microquartz framework occurred through mechanical and light sour oil, hard over-pressures, and a high porosity, low chemical compaction. permeability silica matrix rich in organic matter. The first two Al Noor wells encountered over 300 meters of pay with Porosity in hydrostatically-pressured silicilyte generally a permeability-thickness product of 8 to 9 microDarcy meter decreases with increasing depth. Overpressured wells depart 6 3 permeability. Reserves of 15.0 x 10 m oil were established from this porosity-loss trend by having higher porosity for 6 3 from expectation oil-in-place of 210 x 10 m . Production an equivalent burial depth, probably because overpressures tests have shown both the challenges and the opportunities retard/inhibit compaction and/or cementation. Fluid to produce from the unique reservoir. The play has no direct inclusion data indicate the presence of early hydrocarbons geological analogues, hence understanding the depositional in fracture-filling quartz cements at temperatures of 70- environment and the development of reservoir quality were 80°Centigrade. These temperatures correlate with the amongst the critical success factors which were addressed modelled temperatures at which hydrocarbon generation in a multi-disciplinary study. started in the silicilyte. The loss of overpressures at any stage in the burial history of a silicilyte slab resulted not only in The Athel silicilyte is part of the Athel Formation (Vendian loss of hydrocarbons but also in a resumption of porosity to Early Cambrian Huqf Supergroup) of South Oman. The loss by compaction and cementation. paleogeographic setting at the time of deposition was a restricted shallow-marine basin, most probably a rift-basin The results of the multi-disciplinary study greatly improved setting, bounded by carbonate platforms along the rift the understanding of the depositional environment and the margins. The deeper parts of the basin were periodically development of reservoir quality and were used to refine anaerobic, resulting in the preservation of substantial prospect evaluation and to optimize field development. amounts of organic matter and the formation of hydrocarbon source rocks of exceptional quality and thickness, one of Joachim E. Amthor (see abstract "Sedimentology, which is the Athel Formation silicilyte. Present-day thicker Diagenesis and Charge History of the Haima Deep Gas (distal) silicilyte sections tend to have a higher average Reservoirs in North Oman: An Integrated Approach to Play porosity than thinner (proximal) sections. The highest rates Evaluation" on facing page for biography and photograph) of accumulation are likely to have been in the distal parts of the silicilyte half-graben setting away from the source of Tom Faulkner is a Senior Seismic clastic and carbonate input. Interpreter in the Exploration Department at Petroleum Typically for the silicilyte are finely laminated, porous Development Oman (PDO). Tom’s lithofacies which can reach thicknesses of over 300 meters. main responsibilities are prospect The rock matrix consists of up to 80% of microcrystalline evaluation, applied sedimentology quartz with high amounts of microporosity (up to 30 pu). and integration with seismic data. The very small modal crystal size of 2-3 microns explains Before joining PDO in 1994, he was the microDarcy permeability. The silica matrix is considered employed as Sedimentologist by Shell to have been biochemically precipitated as primary micro- International and Shell Research in crystalline quartz at low temperatures. The Netherlands. Tom has a BA (Honors) in Geology from Oxford University and a PhD from Bristol University. The Athel silicilyte is also a world-class source rock, with total organic carbon (TOC) values up to 6 wt-% and Neil L. Frewin (see abstract "Oil Families of Oman" on hydrogen indices in excess of 400 mg HC/g TOC. However, page 55 for biography and photograph) traditional TOC evaluation methods do not readily apply, mainly due to the presence of the significant liquid oil phase during increased maturation. Furthermore, the oil is not

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Jean-Louis Alixant is currently exploitation tool. A large (7 OCS blocks) 3-D vertical cable responsible for Athel petrophysics in survey was acquired in the Gulf of Mexico, processed Petroleum Development Oman through Pre-Stack Depth Migration, and compared directly (PDO). Jean-Louis joined Shell with a conventional 3-D horizontal streamer survey. Both International as a Petrophysicist in were acquired and processed for the purpose of making a 1990, and worked initially on controlled comparison. Care was taken to make the quantitative seismic inter-pretation processing of the two distinct data sets as close to each other and pore pressure evaluation at Shell as was possible. The only processing differences allowed Research. He was then assigned to were those necessitated by the fundamental differences of Shell Gabon where he held positions the two data sets. This paper describes the processing as Economics Engineer, Technology Planner, and performed on the data with emphasis on those aspects of Petrophysicist. He joined PDO’s exploration team in 1996. vertical cable processing which contrast with conventional Jean-Louis graduated from Institut Industriel du Nord (1986) streamer survey processing. and Institut Français du Pétrole (1987), and earned a PhD in Petroleum Engineering from Louisiana State University There are several inherent operational advantages to vertical in 1989. He has a keen interest in reservoir surveillance, cable acquisition when compared to streamer acquisition. nuclear magnetic resonance, measurement while drilling, The receiver cables are anchored to the water bottom well and resolving complex reservoir characterisation problems below the water surface so that towing noise is eliminated through data integration. and surface wave noise is reduced. The small horizontal extent of the cables allows easier deployment near obstacles Albert Matter received his PhD in such as platforms or drilling rigs (Paul Krail; personal Geology from the University of Bern, communication). Switzerland, in 1964. Following post- doctoral appointments at Rice The basic acquisition unit of the vertical cable operation University and Johns Hopkins was a cable containing 16 hydrophones spaced 45 meters University, he returned to Bern in apart anchored at the end to the water bottom and buoys at 1966, where he is now a Professor. the other end to maintain vertical tension on the cable. A His major research interests are in second floating buoy carried the recording system and a tape clastic sedimentology and diagenesis drive for storage of the seismic data. The vertical cable applied to petroleum exploration. survey at any given time had 12 live cables positioned in a Albert and his students are currently working in 3 by 4 array. The inline and crossline spacing of the cable collaboration with petroleum companies in Germany, array were 1,600 meters and 1,800 meters respectively. The Hungary, the Sultanate of Oman and Switzerland. source vessel shot a series of inlines with shot spacing of 50 meters and line spacing of 40 meters over the array with the Karl Ramseyer received MSc (1977) far line of receiver cables being rolled along the survey was and PhD (1983) degrees in Geology extended in the crossline direction. In the end, 99 cable from the University of Bern, positions had been occupied in an area of 14 by 16 Switzerland. After two years as a kilometers. post-doctoral fellow at the University of California, Santa Barbara, he The horizontal streamer survey was a multi-streamer two returned to Bern in 1985 as Assistant boat operation with two vessels towing three cables each. Professor. His research is The length of all receiver cables was 3 kilometers. The two concentrated on quantifying vessels proceeded in aline at a distance of 6 kilometers, so diagenetic reactions and the effect of that the second vessel towing the source array recorded organic matter on mineral diagenesis. offsets out to 3 kilometers and the first boat recorded offsets 3 kilometers to 6 kilometers.

Relatively large scale acquisition of vertical cable seismic 3-D Vertical Cable Processing data is operationally viable in the Gulf of Mexico deep water area. From preliminary analysis of the data, it is clear that John Anderson, Ilkka Noponen, the vertical cable method based on a sparse receiver array Wenying Cai, Helen Delome and dense source pattern yields processed seismic data that PGS Tensor are remarkable similar in amplitude and character to data Dwight Sukur and Sandra Boyd acquired more conventionally by towing streamer cables. Texaco E&P (biographies and photographs for John Anderson, Ilkka A new method of seismic data acquisition, the vertical cable Noponen, Wenying Cai, Helen Delome, Dwight Sukur, marine survey, has been verified as a viable exploration- Sandra Boyd are unavailable)

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Subsalt Depth Imaging Using 3-D VSP The final migrated 3-D volumes of both walkaway VSP surveys were loaded on a workstation and interpreted. The Technique in the Ras El Ush Field, data allowed the mapping of reliable horizons beneath the Gulf of Suez, Egypt evaporite section which absorb most of the reflection energy. Three key horizons have been picked and structural maps Mohammed A. Badri have been derived in depth. Key faults affecting the reservoir Wireline & Testing geometry were identified and included in the maps. The Taha M. Taha derived maps have significantly improved the definition of Gebel El Zeit Petroleum Company the field and helped in detecting promising blocks. and Robert W. Wiley Company Mohammed A. Badri is based in Egypt and is Schlumberger's Senior Subsalt imaging in the Gulf of Suez is a difficult problem. Geophysicist for the East Although 3-D surface seismic data has significantly Mediterranean Region covering improved our understanding of the structural and Egypt, Turkey, Syria, Jordan and stratigraphic elements dominating a given reservoir, Sudan. He graduated from the however, in certain cases it proved to be limited. In the Ras University of Minnesota, USA, in El Ush field, Gulf of Suez, hydrocarbon was discovered in 1985 with a PhD degree in the pre-Miocene section in the Matulla and Nubia sandstone Geophysics. He worked for King formations based on an aeromagnetic anomaly high in which Saud University, Saudi Arabia, as a the basement appeared to come close to surface. The Professor of Geophysics from 1985 to 1990. In 1990 he reservoir showed a dip magnitude of about 42 degrees to joined Schlumberger Wireline and Testing Services in Saudi the southwest. After drilling several delineation wells based Arabia. Currently, he is in charge of borehole seismic and on geological modeling it was observed that the field was sonic services including data acquisition, processing, far more complex than originally anticipated due to the interpretation and development. His main interests are presence of a thick South Gharib salt section and two tectonic reservoir imaging technology, anisotropy, permeability and trends breaking up the field into several titled and rotated shear waves. He is a member of the SEG and EAGE. compartmental blocks. Since the reservoir is less than 2,000 meters deep and part of the field resides in shallow water, Taha M. Taha is the Geophysical the acquisition and processing of 3-D surface seismic would Sector Manager for Gebel El Zeit be costly, with long turnaround time on processing and may Petroleum Company, Cairo, Egypt. not produce the desired results for understanding the He graduated from the University of structural settings and support successful development well Alexandria in 1966 with a BSc in drilling. Geology. He obtained a Diploma of High Studies in Geophysics and a A delineation well was drilled but it did not encounter the Diploma of High Studies in reservoir due to the presence of a fault which was not Petroleum Geology in 1970 and anticipated. A 2-D walkaway VSP profile was acquired 1972, respectively, from Ain Shams and clearly revealed the presence of a cross element fault. University. He worked with several oil companies including This success lead to the acquisition of the first 3-D VSP Marathon Petroleum Egypt, Bahrain National Oil Company, survey in Egypt and the Middle East in two different wells ALGEO in Algeria, Sonatrach Exploration in Algeria and with deviation of about 60 degrees. A multi-component General Petroleum Company in Egypt. He is a member of downhole seismic array was used in the 3-D VSP acquisition. the SEG and AAPG. Both surveys were successfully acquired and processed in a remarkably short time. The 3-D VSP migration process Robert W. Wiley is an Advanced required the building of an accurate velocity model. 3-D Senior Geophysicist with Marathon depth model building is based on geometric elements Oil Company. Bob has worked with represented by formation boundaries and faults which Marathon since 1973. He started in delimit each volume. A volume unit can be assigned the Production Technical Services properties such as velocity, density and dip. Layer Department, moved to Research, and tessellation, a process which divides the layered velocity was recently transferred to Technical model into tetrahedra, was performed. Interval velocities Support. Bob holds a BSc degree in were assigned to each subvolume and stored at each corner Math (1971) from Colorado School of every tetrahedra. Ray tracing was then performed for of Mines and a PhD in Geophysics several lines and look up tables were generated for input to (1980) also from Colorado School of Mines. His current the Kirchhoff depth migration algorithm. Migration control interests are seismic modeling and inversion, VSP processing parameters such as dip and aperture were carefully selected and imaging. to produce optimum results.

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In our paper we will present outcrop data, satellite imagery, Foreland-Basin Development and and plate and cross-section reconstructions that illustrate Petroleum Migration in the key features in the development of the Zagros and Oman Zagros and Oman Mountains foredeeps. The development of these foredeeps and the thermal effects their creation had on source rocks in the Ian R. Baron, Conoco Middle East Ltd., Paleozoic, Mesozoic and Tertiary, created a complex Robert J. Hooper and Mehdi Alavi hydrocarbon system in which different hydrocarbon phases Conoco Inc. were generated at different levels at different times in different places! The application of modern concepts of The concept of the foreland-basin system has evolved foreland-basin development, combined with paleo- considerably in recent years. Of particular significance to reconstructions of the Arabian Plate and modeling of the petroleum system analysis is the recognition that foreland thermal history, provide the first step in defining optimal basins are dynamic systems and that there is considerable areas for future exploration. overlap and interaction between the orogenic wedge and its associated foreland-basin system. Early-formed strata in Ian R. Baron is Vice President and the foreland basin, can be progressively incorporated into Manager of Conoco's Middle East the orogenic wedge. The recognition of distinct phases of Business Development office, based foredeep development associated with the Late Cretaceous in Dubai. Apart from a brief spell to present day shortening in the Zagros and Oman Mountains working in the North Sea and is critical to understanding the petroleum system of the Australia, most of his career has been eastern Arabian Plate. spent working in the Middle East. For the last 10 years he has worked The northern margin of the Arabian Plate stabilized with DPC, Conoco's operating unit following the Permo-Triassic break-up of Gondwana and in Dubai, and with Conoco's Mideast carbonate deposition persisted over most of the platform. New Ventures Group. He obtained a BSc (Honors) in Development of the foreland-basin systems began in the Geology from the University of Manchester in 1977. Ian is Cenomanian/Turonian as a northeastward-directed a member of the AAPG, SEE and the Geological Society of subduction zone, within Neo-Tethys, began to impinge upon London. promontories on the Arabian margin. Emplacement of the orogenic wedges depressed the margin and created a series Robert J. Hooper has been with of foreland-basin systems, the effects of which were widely Conoco in the capacity of Senior felt over the platform. Continued encroachment onto the Research Scientist since 1991. His Arabian margin ultimately caused the emplacement of primary function is to serve as a ophiolite suites Ð the ophiolites of Kermanshah, Neyriz, consultant to worldwide exploration and the Oman Mountains Ð into the embayments on the groups on matters of structural Arabian margin. In Iran, the carbonate bank retreated rapidly geology, the interpretation of to the southwest, and a flysch/shale apron developed in front structures in seismic data, and regional of the advancing allochthons. For the first time since the tectonics. He is also involved in breakup of Gondwana, the dominant source for siliciclastic research into structural development deposition on the northern margin of the Arabian platform in a wide variety of tectonic settings, and monitors several was from the north-northeast, a situation that would remain external research programs. Prior to joining Conoco, Robert to the present day. The margin gradually stabilized following was an Assistant Professor at the University of South Florida the emplacement of the allochthons and the early foredeep (1984-1991). He received a PhD in Geology from the progressively filled. The flysch/shale/carbonate system University of South Carolina in 1986. He is a member of the retracted towards the allochthons and the carbonate bank GSA and the Geological Society of London. once more built-out over the earlier foredeeps. By the Neogene the northeast margin of the Arabian platform had Mehdi Alavi is a Structural/Tectonic fully docked with Eurasia and the intervening Geologist and Basin Analyst with microcontinents of Central Iran. In Iran, rocks deposited in Conoco’s Advance Exploration the Late Cretaceous foredeeps became progressively Organization. He received a BSc imbricated and incorporated into the developing Zagros fold from Tehran University, a MSc from belt. Evaporitic and molassic sedimentation eventually the City University of New York, and succeeded the stable-platform carbonate facies as the new a PhD from the University of foredeep which developed in association with the developing Massachusetts at Amherst. He has Zagros orogenic wedge progressively advanced from the carried out several research projects northeast. concerning various aspects of the

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orogenic belts in the Middle East and the Appalachians of First, the single T2 cutoff approach is an over simplified North America. He established the Research Institute for interpretation strategy. Second, obtaining a thorough Earth Sciences of the Geological Survey of Iran (GSI) and interpretation requires using the core and log data within was Deputy General Director of GSI between 1995 and the context of the reservoir formation. In other words, solid 1996. Mehdi is a member of the GSA and the International interpretation strategies must employ a certain amount of Association of Structural/Tectonic Geologists (IASTG). upscaling.

One way to upscale is to package a sequence into units based on a set of uniform criteria. Sedimentologists use this Getting Maximum Value from NMR Data: approach to perform facies analysis. The NMR signal New Developments in contains both pore size and fluid distribution. We therefore Core-to-Log Calibration reasoned that vertical changes in wireline-log NMR distributions also reflect changes in rock properties. We Paul B. Basan call these packages NMR Facies to distinguish them from Applied Reservoir Technology facies used by sedimentologist.

The fundamental NMR response is a measure of the proton NMR distributions, especially those generated from log data, decay in fluids confined within the rock. NMR instruments are not easy to interpret from visual inspection. produce a distribution of echoes from the decay of signal Consequently, developing NMR facies requires a reliable amplitude, over a period of time, commonly called the time- way first to identify similarity or dissimilarity and, second, domain data. Few petrophysicists work with these data a reliable way to package the units into facies. Statistical preferring instead to interpret rock properties from processed techniques, especially principle component analysis and echo trains. Processing procedures use an inversion (fitting cluster analysis, provide the tools required to interrogate and smoothing) algorithm to produce the familiar frequency NMR data and develop NMR facies. patterns, known as T -domain data. 2 Going from an individual NMR distribution to a set of Fitting data sometimes creates distributions where no similar distributions, and then packaging them into units is meaningful signal actually exists. However, virtually any a useful upscaling procedure for comparing the NMR response to core descriptions, borehole images, other petrophysical interpretation made using T2-domain data can also be made using time-domain data (e.g. porosity and wireline logs and, ultimately to reservoir-scale models. BVI). The advantage of using time-domain data is that the However, NMR facies analysis (NFA) serves an even more interpretation depends on the actual quality of the signal. important function for log interpretation. Changes in the Using this approach not only furnishes an interpretation but characteristics of the NMR signal usually reflect changes in also a QC/QA check. pore geometry, fluid content, and other parameters that may signify a change in the T2 cutoff needed to interpret BVI. NMR core analysis databases provide a way to determine NFA identifies these changes, and therefore provides the basis to develop a T cutoff customised to the individual both the range of the T2 cutoff, and its dependency on other 2 petrophysical parameters, in formations having different facies. rock and pore types. Previously the NMR interpreters placed considerable emphasis on substituting a single core-derived Paul B. Basan received his BSc in cutoff for the default cutoffs used by the wireline companies. 1965 from Indiana University and an Logically, given the amount of variability shown in NMR MSc in 1970 from SUNY Binghamton. Upon completion of his databases, the idea of measuring the T2 cutoff in a series of core plugs, taking the central tendency of the data, and using MSc Paul worked for Texaco as an it in place of the default cutoff was a nice idea, but one that Exploration Geologist. In 1971 he seldom provides the best interpretation. We now recognise attended the University of Georgia that log analysts cannot use core data directly for deriving where he received a PhD in Geology an interpretation. and again returned to the industry as a Research Geologist for Amoco. Matching the NMR signal from a core plug to the rock Since 1978, Paul has held several positions in exploration formation requires a thorough understanding of the signal, and management and founded Applied Reservoir Technology the response to rock formations, and the variations imposed in 1988. by pore geometry and fluid type. Any log interpretation based on default, or core analysis parameters usually lacks precision without taking these factors into consideration. These complications lead to some unavoidable conclusions.

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Geological-Geophysical Prognosis of Oil Gulara A. Bayramova graduated from Azerbaijan State University. and Gas Potential of Mesozoic Volcanites She has a PhD degree in Geology and in the Kura Depression Mineralogy. Gulara is a Geological and Petrological Engineer with the Gulara A. Bayramova Geology Institute of Azerbaijan Geology Institute of Azerbaijan Academy of Sciences academy of Sciences. Her main areas of scientific interest are studying the In the Kura depression, the major prospects for the increase specific features of geological in hydrocarbon reserves are tied to the Mesozoic structures by interpreting geophysical deconsolidated volcanogenic reservoir rocks. In this work, materials, describing oil and gases from the point of view of search for ways of forecasting such type reservoir rocks in geochemistry and the geochemical and geophysical methods a sedimentary section, as well as of localizing within those of searching for hydrocarbon deposits in sedimentary basins. oil and gas-bearing zones, with regard to the central part of She has published numerous papers and is a member of the the Kura depression in Azerbaijan, were carried out by EAGE and Azerbaijan Petrologist and Geologist Society. employing geological-geophysical and gas-geochemical data.

On correlation between the anomalies of the gravitational Development Drilling of the Tawila Field, and magnetic fields, and the findings of seismic and electrical Yemen, Based on Three-Dimensional prospecting, the depths and spatial contours of protrusions Reservoir Modeling and Simulation of the Mesozoic volcanites are determined. We have substantiated a complex of gas-geochemical characteristics Craig I. Beattie, Brian R. Mills with respect to the areas where in the section the Mesozoic and Virginia A. Mayo deconsolidated volcanogenic rocks occur (including the Canadian Petroleum International Resources Ltd. Muradkhanly oil field). The presence of contrasting high values for the near surface anomalies of heavy and light Canadian Petroleum International Resources Ltd. and hydrocarbons, above the volcanogenic reservoir rocks, is a partners in the Yemen Masila Block have successfully used sign of likely presence of oil and gas in individual areas. A detailed three-dimensional reservoir modeling and reservoir number of factors such as basement protrusions, velocity simulation to optimize the development of the larger oil inversion, the high electric conductivity of the section, and fields in the Masila area. The models were used to predict gravitational and near surface hydrocarbon anomalies, has reservoir performance and plan additional development established certain regularities for the occurence of the drilling which subsequently demonstrated that the models Mesozoic volcanites, as well as non-traditional oil and gas accurately predicted drilling results. traps associated with them. The main producing horizon in the Masila area is the An area characterized by low values of the velocity of the Cretaceous Upper Qishn Formation, a clastic-dominated longitudinal elastic waves has been detected in the site of transgressive depositional sequence with fluvial sediments Saatly super-deep well (near Muradkhanly) at the depth at the base, tidal dominated estuarine sediments in the range 3,540 to 4,060 meters. This interval with the velocity middle, and marine shoals at the top. This variable array of decrease of 0.6 kilometer per second, from 5.3 kilometers facies presents modeling challenges but the resulting per second to 4.7 kilometers per second within 710-740 heterogeneous models provide a realistic representation of meters depth range, is related to the roof of the volcanites actual reservoir characteristics. This paper describes the of the Mesozoic basement. This velocity inversion interval approach used to stochastically distribute both facies bodies corresponds to the deconsolidated roof of the Cretaceous and petrophysical parameters, and to upscale the model for Volcanites of the Mesozoic Basement. These anomalous reservoir simulation, while preserving the complex reservoir volcanogenic rocks form a new type of reservoir Ð description. Muradkhanly oil field Ð and trap the bulk of the field's oil reserves. The nature and extent of the fluid saturation in The Tawila field was the first Masila field to have wells these reservoir rocks can be mapped by the amplitude of drilled on the basis of the modeling effort, with very the seismic reflection. encouraging results. For these new well locations, the model successfully predicted both reservoir development and oil- Based on the results of the data interpretations, the maps water contact movements resulting from production from and profiles of the prospective oil- and gas-bearing zones existing wells. This paper presents key conclusions and for individual areas (Muradkhanly, Agdam-Khachinchay predictions from the modeling and reservoir simulation, and etc.) were made and exploration well sites identified.

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compares them to the results from subsequent drilling. As Improved Modeling of Matrix-Fracture a result of the successful development drilling, these models are now an integral part of reservoir management and Transfer Terms in development planning for all Masila fields. Dual Porosity Simulators

Craig I. Beattie is the Reservoir Bernard Bourbiaux and Jean-Claude Sabathier Engineering Manager for the Yemen Institut Français du Pétrole Operations Group of Canadian Petroleum International Resources The long-term behavior of naturally-fractured reservoirs Ltd. (CPIRL). Prior to assuming his during exploitation mainly depends on the flow exchanges current position he was the Project occurring between the high-capacity matrix medium and Leader for the Masila Modeling the high-conductivity fracture medium. Dual-porosity Project and Reservoir Engineer for simulators have been designed to simulate this specific flow the Tawila field. Craig has 17 years behavior. They involve the use of two superposed grids, a of reservoir engineering experience, matrix grid and a fracture grid, with matrix-fracture transfers primarily in reservoir management, reservoir simulation, being computed at each gridlock location. and . Prior to joining CPIRL in 1994, he worked for 14 years at a major oil company. He holds To obtain reliable predictions, the physical mechanisms BSc and MSc degrees in Chemical Engineering from the contributing to these transfers must be identified, and an University of Toronto. adequate formulation has to be used at gridlock scale in order to correctly simulate the kinetics of matrix-fracture fluid Brian R. Mills graduated from exchanges as well as the final saturation of matrix blocks. McGill University with Honors in However, these formulations remain very approximate Geological Sciences in 1977. He has because matrix blocks are not discretized. Therefore, pseudo 20 years of experience as a geologist kr-Pc curves, to be input in the dual-porosity simulator, have in the petroleum industry with more to be calibrated from a finely-gridded single porosity model than ten years in the international before running any field-scale simulation. Such an approach sector at Canadian Occidental and is time-consuming and generally not satisfactory for long- Canadian Petroleum International term production forecasts. Actually, the calibration of Resources Ltd. He has worked in a transfer terms through pseudo kr-Pc curves is valid for a variety of roles in Canadian given physical mechanism, whereas the whole field life most Occidental’s international petroleum exploration, business often involves a combination of different mechanisms. development and development endeavors. He is currently a Senior Geoscientist with the Yemen Operations Group and Institut Français du Pétrole has been developing a has been an active participant in the company’s recent three- formulation which improves the representation of flow dimensional geological modeling project for the Masila mechanisms involved in matrix-fracture transfers. In this Block fields in Yemen. paper, we present the water injection case and show how we can accurately simulate the matrix-fracture flow Virginia A. Mayo is a Reservoir exchanges linked to capillary imbibition, including a Analyst in the Yemen Operations possible effect of gravity forces. Group of Canadian Petroleum Inter- national Resources Ltd. (CPIRL). The improved formulation of capillary imbibition takes into She has been working on the Masila account the gradual water penetration in matrix blocks project for 6 years in roles of surrounded by water-filled fractures. At matrix block scale, increasing responsibility. She has results are very consistent with a finely-gridded single- worked on the Tawila field since porosity model, whatever the block shape and rock-fluid 1996, and is currently responsible for data. If significant, the effect of gravity forces can also be all reservoir engineering for the field. implicitly taken into account in the formulation. Prior to joining CPIRL, Virginia worked at the Saskatchewan Research Council. She holds a Certificate Water injection was then simulated in a cross-section of a in Petroleum Technology from the Southern Alberta Institute typical fractured reservoir in order to quantify the practical of Technology. impact of this new formulation. The previous and new formulations of capillary imbibition transfers lead to significantly-different predictions of water-oil ratios, especially in the presence of large matrix blocks. The simulations also indicate that the formulation correctly accounts for the contribution of gravity forces to matrix oil

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recovery, which may be important for intermediate- characteristics match the quantities to be measured, a plot wettability rock-fluid systems. of the predicted characteristics versus along hole depth produces a synthetic or simulated log. This may determine Such results demonstrate that the proposed representation the choice of tools, the required tool specifications, of matrix-fracture transfers, which requires to input only centralized running, cable speed, position of stations, logging the actual petrophysical properties of the matrix medium, is time at stations and many other operational parameters. In worth being introduced in dual-porosity simulators for addition, the synthetic logs may be used to compare predicted reservoir engineering applications. versus real production behavior once logging has commenced. Bernard Bourbiaux is a Research Engineer in the Reservoir Modeling A software package that produces simulated logs based on Group of Institut Français du Pétrole. simple well data, i.e. production history data, deviation or He has been working on various survey data, completion information and fluid PVT topics related to the simulation of properties was used to draft logging programs for 6 wells in naturally-fractured reservoirs since Oman. The package uses a sophisticated two-phase flow 1994. Bernard was in charge of model that has been extensively validated on both pipeline laboratory studies of multi-phase and well data. The software is easy to use and fast so that flows in porous media from 1982 to case studies can be generated quickly and the effect of 1994. Bernard holds a BSc degree various inflow profiles on the simulated logs can be in Geology from ENSG, Nancy and MSc degree in Reservoir evaluated. Sample results from the pre-job planning include Management from ENSPM, Rueil, France. the selection of stations, the choice of and specifications of tools and the generated simulated logs. Jean-Claude Sabathier is Associate Director of Research at Institut Olaf Bousché is currently Français du Pétrole (IFP) in charge responsible at the Shell International of the coordination of projects on E&P Research and Technology reservoir characterization. Before Service Center for contacts with joining IFP in 1993, he was scientific Western Atlas International on manager of Beicip-Franlab for 22 production logging issues. In years, in charge of the supervision of addition, he is part of the team the Reservoir Group. He was also working on the advancement of the attached to the Ministry of Industry, capabilities of production logging in France, as an expert on French oil and gas supplies. Jean- horizontal multi-phase producers. Claude holds a MSc degree in Aeronautical Engineering Olaf joined KSEPL in 1993, starting in the Quality and from ENSAE, Paris and a post graduate degree in Petroleum Production Measurements Section working on a diverse Engineering from ENSPM, Rueil, France. range of subjects. In 1996 he started working on multi- phase flowmeters for surface operations and on capacitance based instruments in particular. He joined the Rock and Pre-Job Planning of Production Logs Fluid Property Evaluation Contract Center in 1997. Olaf holds an MSc in Applied Physics (Non-Newtonian Fluid in Multi-phase Horizontal Wells: Properties) from University of Enschede, the Netherlands Multi-phase Flow Model Assisted (1986) and a PhD in Biophysics (Advanced Infrared Well Log Programming Techniques for Protein Study) from Boston University in 1993. Olaf Bousché, Alex van der Spek Shell International Exploration and Production BV Alex van der Spek received a PhD Hassan A. Al-Nasser, Petroleum Development Oman in Physics (Laser Spectroscopy) from David Chace, Darryl Trcka Eindhoven University of Technology and Crawford Anderson in 1992 after completing a MSc in Western Atlas Logging Services Physics (Theoretical Aerodynamics) at the same institution. Present day The ability to predict generic flow characteristics in multi- prime responsibility of Alex is to phase, horizontal producers (flow regime, liquid hold up, substantially advance the capabilities pressure gradient and actual liquid and gas velocity) which of production logging in horizontal any production logging tool attempts to measure would multi-phase producers. This entails greatly facilitate the planning and programming of both new technology hardware and advanced, multi-phase production logging operations. Since the predicted flow-model assisted interpretation of production logs. Alex

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recently joined the Rock and Fluid Property Evaluation Seismic Imaging of Geologically Contract Center of Shell International E&P to continue working on production logging in horizontal wells. Complex Areas

Hassan A. Al-Nasser graduated with Keith Branham, Kay Dautenhahn Wyatt, a BSc in Petroleum Engineering from Paul Valasek and Brackin Smith the University of Southern California, Phillips Petroleum Company Los Angeles, USA. He joined Petroleum Development Oman There is an increasing amount of exploration work in areas (PDO) in March 1982. After the well- of complex geological structure and strong velocity site period, he worked as a contrasts. Conventional 3-D seismic processing in the time Petrophysicist in various PDO domain has proven inadequate to image these areas. Depth concessions in Oman, covering imaging technology, in the post-stack and pre-stack domain, carbonate and clastic reservoirs. can provide significantly improved images. Obtaining Hassan is currently working as Petrophysicist in the Yibal reliable depth seismic images in areas of complex geology team and is focal point for special production logging requires proper application of techniques in acquisition, applications and cased hole logging in PDO. processing, velocity modeling and imaging. Each of these steps can play a critical role in the quality of the final seismic David Chace is a Project Leader in image. the Engineering Department of Western Atlas Logging Services. Location, orientation and geometry of the acquisition David received a BSc in Physics from equipment can lead to different subsurface images. the University of Rhode Island. He Acquisition geometry type and source-receiver offset has been involved with development distribution can affect subsurface illumination and velocity of pulsed neutron logging instruments estimation. Examples of these acquisition effects will be and interpretation, including C/O, shown. PNC and oxygen activation logging. He worked for several years in To properly image seismic data, both the structure and Malaysia and Saudi Arabia and was responsible for pulsed velocity of a layer are needed. A proprietary velocity neutron and production logging and interpretation. He is estimation package, VEST3D, has been developed to derive currently the Project Leader for the Multi Capacitance 3-D seismic velocity models. We will review the techniques Flowmeter. and application of this technology for real data cases. Case history examples will be shown comparing various post- Darryl Trcka is a Senior Research stack and pre-stack depth imaging algorithms. Physicist in the Nuclear Research Department of Western Atlas Logging Keith Branham received a BSc in Services. He received his PhD in Geology from Southwest Missouri Nuclear Physics from Florida State State University in 1984 and an MSc University and joined Western Atlas in Geophysics from the University of in support of logging programs at the Kansas in 1986. He joined Phillips nuclear test site in Mercury, Nevada. Petroleum Company in 1986 as a He is currently the Project Leader for Processing Geophysicist. Currently the Pulsed Neutron Holdup Imager. he is Team Leader of the 3-D Processing and Advanced Imaging Crawford Anderson graduated with Team where he is active in 3-D model a BSc in Physics from the University building and depth imaging. Keith is a member of the SEG of Birmingham, England. He joined and the Geophysical Society of Tulsa. Western Atlas in 1980 and held various positions in operations and Kay Dautenhahn Wyatt received a technology development. He is BSc in Electrical Engineering from currently in The Hague, Netherlands the University of Tulsa in 1976 and working as Business Development an MSc in Electrical Engineering Manager, responsible for interfacing from Oklahoma State University in with Shell International Exploration 1977. She joined Phillips Petroleum and Production. Company in 1977 as a Research Geophysicist, and began application of signal processing principles to seismic data processing. In 1979, Kay

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began research in vertical seismic profiling and helped by three discrete, intersecting zones of deformation which pioneer VSP imaging techniques, including the VSPCDP have controlled its structural evolution, resulting in transform. In 1982, she began research in 3-D seismic significant differences in development to the main part of imaging, geological modeling, and velocity estimation. the salt basin. From 1988 to 1995, she served as Project Manager for the advanced seismic imaging group at Phillips. Kay is currently To the east, the Huqf Arch has been a persistent high a Research Leader with Phillips. She has published throughout the Phanerozoic. It probably developed initially numerous papers and holds several patents in the area of as the eastern flank of the rift basin and has been enhanced seismic imaging and vertical seismic profiling. She has by continental breakup and transform faulting along the east served in several capacities to the SEG, most recently as coast of Oman. Transpression along this zone has caused the SEG First Vice President for 1996-1997. repeated episodes of uplift and erosion on the east flank of the salt basin throughout the Phanerozoic. Paul Valasek received a BSc in Geophysical Engineering from To the north lie the Oman Mountains which developed in Montana Tech in 1984, a MSc in response to two discrete phases of compression in Late Geophysics from the University of Cretaceous and Late Tertiary time. A west/east oriented Wyoming in 1987 and a PhD in foreland basin formed in the north of the block in response Geophysics from the Swiss Federal to the first compressional phase. In contrast regional uplift Institute of Technology in 1992. Paul and erosion has typified the Late Tertiary phase of joined Phillips Petroleum Company compression. in 1992 where he has conducted research in 3-D seismic imaging. He To the west, the Maradi fault is a major strike-slip zone which is a member of the SEG and GST. has controlled the degree and style of inversion caused by mountain building. Its role was particularly important during Brackin Smith is a Research the Late Tertiary phase of compression when it appears to Geophysicist at Phillips Petroleum have formed the southwestern limit of regional uplift and Company currently applying wave inversion. equation methods to improve seismic imaging in areas of complex geology. As a result of these tectonic events, the salt has been He received a PhD in Physics from repeatedly mobilized. Paleozoic flowage was mainly lateral the University of Texas at Austin in resulting in low relief salt withdrawal basins and turtle- 1991, where he studied X-ray structures. In contrast, strongly pronounced upbuilding emissions from a tokamak plasma. during Tertiary times has resulted in the development of Upon completion of his PhD, Brackin several large domes. Severe erosion, related to thrust- began work with Phillips as a Research Geophysicist, induced uplift, may have been instrumental in this phase of working on crosswell seismology and elastic wave modeling salt movement. of seismic data. He is an active member of the SEG, serving on the Research Committee. He recently organized the SEG The interplay of tectonics and salt movement has constantly Summer Research Workshop, and co-organized a workshop modified basin architecture, controlling sedimentation and, at the Denver SEG on Seismic Data Compression. Brackin more crucially, modifying trap geometries. Previous is also active in the Geophysical Society of Tulsa, serving exploration in the block has mainly targeted young salt as President for 1997-98. structures. As most hydrocarbon generation in the block occurred in the Paleozoic and Mesozoic such structures require re-migration for success. In the present exploration Development of the Northeast phase Nimir is concentrating on older structures, which were present prior to hydrocarbon generation, and have suffered Ghaba Salt Basin, Block 3, Oman minimal subsequent disturbance.

Joseph Brannan and Stephen F. Flanagan The evolution of the basin will be demonstrated by means Nimir Energy Services Ltd. of a regional seismic grid which will also show the range of plays present in the area. Block 3 lies in the northeast of Oman. The northwest corner of the block is underlain by part of the Ghaba Salt Basin Joseph Brannan is an Exploration Geologist with 16 years whilst the rest of the block is dominated by the flank of the experience in the upstream petroleum industry. He joined Huqf Arch. The basin formed by crustal extension during British Petroleum from university in 1982 and spent 10 years Infracambrian times and since then it has been subject to working on a range of major petroleum provinces including numerous tectonic events. Present day it is circumscribed the North Sea, North Slope, Papua New Guinea, the Sub-

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Andean basins and the Middle East. A model for the sedimentary evolution of the Haima He joined Nimir in 1992 and since Supergroup is proposed. This study concludes that cyclicity then his major areas of interest have in the shallow-marine deposits is probably controlled by been North Africa, the Middle East fluctuations in relative sea level, whilst climatically driven and Colombia. He is currently fluctuations in the paleo-water table may control the cyclicity Geological Manager overseeing of facies distribution in the continental part of the Nimir-operated acreage in Yemen, Supergroup. Larger-scale facies changes are probably Oman and Tunisia/Libya. Joe holds controlled by an interplay of climatic change and changes a BSc in Geology from Glasgow in relative sea level. University and a D. Phil. from Oxford University. He is a fellow of the Geological Society and a Rebecca C. Buckley received her BA member of the PESGB. in Geological Sciences from the University of Cambridge in 1993. Stephen F. Flanagan is a Senior This was followed by a Petroleum Geophysicist with over 17 years Development Oman PhD studentship experience in the oil industry. He at Birkbeck College, University of joined Geophysical Services London, on the Sedimentology of the International from university in 1980 Cambrian of east-central Oman. and spent 5 years on interpretation Rebecca currently works as a and processing projects for the client Production Geoscientist for Esso UK. Saudi Aramco. He then joined British Petroleum and spent 8 years working Neil A. Harbury (see abstract "A Regional Sedimentological on a variety of exploration and Study of the Lower Cretaceous Shu'aiba Formation in production licences both internationally and in the UKCS. Oman" on page 53 for biography and photograph) In 1993 he became a consultant working for companies such as Bow Valley (UK), British-Borneo, Mobil, BP and Oryx Henk H.J. Droste joined Shell in Energy. In 1997 he joined Nimir Energy Services Ltd. where 1984 after receiving his MSc in he is responsible for geophysical activities in the Oman. Geology from the University of He holds a BSc in Geological Sciences from Leeds Amsterdam. He worked as a University. Carbonate Geologist with Shell Research in The Netherlands and as a Sedimentologist in the Regional Studies Team of Shell Expro in The Sedimentology of the Haima London. Henk was posted to Supergroup, Oman: Outcrop Study Petroleum Development Oman in in the Huqf Region 1992 where he joined the Exploration Department as a Geologist/Seismic Interpreter. He is currently working as a Rebecca C. Buckley, Neil A. Harbury Production Geologist in the North Oman Development and Birkbeck College, University of London Production Unit. and Henk H.J. Droste Petroleum Development Oman Derivation of Variable T2-Partitioning The Huqf region is situated along the Arabian Sea coast of east-central Oman. The outcrop area is approximately 60 Coefficient when Core NMR Data by 150 kilometers, and has a core of Infracambrian are Unavailable sedimentary rocks which are onlapped from the west by Cambrian and younger sediments. The Cambrian Haima Hasan A. Bunain, Ahmed A. Latif Supergroup outcrops in a strip, trending from southwest to Kuwait Oil Company northeast across the Huqf region. These outcrops are lateral Mehmet Altunbay and Daniel T. Georgi equivalents of the Haima Supergroup in Oman’s salt basins Western Atlas Logging Services to the west of the Huqf region. Extensive study of these outcrops was undertaken to produce integrated lithofacies The accuracy of bulk volume irreducible (BVI) and BVI- schemes and interpretation of depositional setting for each based permeability estimates can be enhanced by processing of four defined formations. A range of depositional the T2-spectrum data with the correct time-slicing. environments are recognised: from braided fluvial, through Magnetization-decay in smaller pores is faster than the larger playa, aeolian and sabkha to marginal-marine and braid- pores. Hence, a more accurate input of T2-cutoff time delta. reflecting the spectrum of pore sizes under investigation

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yields more accurate estimates of BVI and BVI-based Ahmed A. Latif is a Senior permeability values. Petrophysicist with Kuwait Oil Company since 1982, having 24 years Variable T2-partitioning coefficient for processing NMR- of experience in Geology, log data can be derived from the correlation of core-NMR Petrophysics and Operational data with capillary pressure characteristics of the same set Geology including 4 years with of core plugs. However, most of the time, core-NMR data Kuwait Institute for Scientific are not available due to either the physical condition of core Research. He graduated from Kuwait plugs or lack of them or monetary constraints. This study University in 1973 and is an active explains a methodology for deriving variable T2-partitioning member of the SPE and CSPG. curve when core-NMR data are unavailable. Mehmet Altunbay is a Scientist with The proposed technique requires the availability of either the Reservoir Technology Group at historical core permeability (in-situ conditions), or FMT or Western Atlas Logging Services. He RCI permeability data from the pilot well. The actual T2- is working on Petrophysical cutoff time for a specific depth that corresponds to that of Interpretation of NMR log data. the core plug is determined by calculating the ratio of Mehmet is also involved in the movable to irreducible fluid saturations for different T2- reservoir description aspects of cutoff values. These ratios and the NMR-porosity are entered wireline and core data integration. into the Coates equation for calculation of permeability. He holds BSc and MSc degrees in Then, a permeability value is computed with a constant set Petroleum Engineering from the of coefficient and exponents for each ratio (movable to University of Southwestern Louisiana and Middle East irreducible) that was obtained by changing the T2-cutoff Technical University. Prior to his current position he worked time. This interactive process continues until an acceptable for Core Laboratories-Technology Applications Group, Pal- agreement is reached between the computed permeability Mix Inc., and Turkish Petroleum Corporation. Reservoir and the core, FMT or RCI derived values. The residuals description, formation evaluation and formation damage (core permeability - computed permeability) are calculated prevention have been Mehmet's main areas of interest. and plotted. A random distribution is sought. Any systematic departure in the residual plot indicates a poor fit, probably Daniel T. Georgi is Manager of based on improper selection of either the T2-cutoff time or Reservoir Technology with Western the constant and the coefficients in the Coates equation and Atlas Logging Services. Daniel holds requires an adjustment. The T2-cutoff value is decided as an MSc degree in Geophysics and a the actual T2-cutoff time for the subject depth when an PhD degree in Earth Sciences from agreement between the computed and measured Columbia University. Throughout his permeability values and a random distribution in the residual career Daniel has been involved in plot are obtained. This process is repeated for each depth- fundamental research, tool level with core or FMT or RCI data. The derived T2-cutoff development and field studies. He values are correlated with GR, PE, DT, ZDEN to establish a has dealt with many aspects of model equation for generating the variable T2-cutoff curve formation evalution of conventional, fractured and heavy- where there is no core, FMT or RCI data. The model equation oil reservoirs as well as open and cased hole log analysis. yields a variable T2-cutoff curve that reflects the ever- changing characteristic of pore sizes. The variable T2-cutoff curve betters the accuracy of BVI, BVM and consequently, Predicting Permeability: enhances the accuracy of computed permeability values. Using Mechanical Stratigraphy of Hasan A. Bunian is currently Carbonate Rocks in Neural Networks working as Superintendent of the is a Giant Step Closer Geophysics Department at Kuwait Oil Company. He has 19 years of Mohamed N. Bushara petroleum oil exploration experience. Zakum Development Company Hasan received his BSc in Geology and Laura M. Ogden from Kuwait University in 1979. SAS Institute

We present preliminary results of predicting permeability values using two sector models from a carbonate reservoir offshore Abu Dhabi, United Arab Emirates. The sectors were chosen because of their contrasting geology and

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reservoir properties in order to test the strength of the model. companies with such tasks as using Both core and wireline log data were first scrutinized for Time Series Forecasting methods to quality and data redundancy using elementary multivariate develop forecasting procedures and statistics and then standardized to ensure even contribution models and using Neural Networks from all variables. A neural network model was to develop geological prediction obtained using nine well data variables as inputs and six models. Laura holds BSc and MSc hidden neurons. Even though the model showed very good degrees in Industrial Engineering results per sector, predicting very high and very low from Georgia Institute of Technology permeability values was a problem. where she specialized in Production and Logistics Systems and Statistical Next, geomechanical layers, stylolite and open fracture Process Control and Quality Assurance. density codes from cored wells were input into the neural network model. Three-dimensional geomechanical units were constructed using a merged coding system such that all uncored wells in a particular sector will have a common How to Turn the Geological Image geomechanical strata coding with varying corresponding of a Fractured Reservoir into a depths. This remarkably improved predictions and resulted Dual-Porosity Model in correlation coefficient between target and predicted permeability values which is an order of magnitude higher Marie-Christine Cacas, Bernard Bourbiaux than the benchmark model. The predicted values were then and Sylvain Sarda conditioned with test permeability to arrive at the final Institut Français du Pétrole numbers. We regard results of this method to be superior to results obtained by conventional methods, which use Both characterization and simulation of naturally-fractured multiple regression transforms even within predetermined reservoirs benefited from major advances in the recent years. petrophysical rock units. This approach efficiently accounts On the one hand, techniques of data integration and 3-D for the low end matrix permeability caused by diagenesis imaging are available to build representative geologic images or pressure solution and the exceptionally high fracture- of fracture networks. On the other hand, multi-purpose dual- related permeability values. porosity simulators have been developed to deal with any scenario of reservoir exploitation. However, the “sugar Mohamed N. Bushara is a Reservoir lump” representation of the fractured medium used in these Geologist with Zakum Development simulators is actually very far from geologic images. Hence, Company, Abu Dhabi, UAE. He the reservoir engineer remains faced with the difficulty of graduated with a BSc (Honors) from parameterizing the dual-porosity model, and particularly of the University of Khartoum, earned finding correct input data for equivalent fracture an MSc degree from the University permeabilities, and equivalent matrix block dimensions. of Washington, Seattle, in 1987, and a PhD from the University of New and systematic methodology and software have been Wisconsin, Madison, USA, in 1991, developed to compute those equivalent hydraulic all in Geology. Mohamed worked for parameters: (1) a tensor of equivalent fracture permeability ARCO Alaska, Inc., between 1991 and 1996, in development is derived from 3-D flow computations in the actual fracture and exploration of North Slope and Cook Inlet fields. He network using a resistor network method; and (2) the was a summer hire for Exxon Production Research Company equivalent block dimensions in each layer are derived from in Houston, in 1989 and a visiting scholar at the Department the identification of a geometrical function based on capillary of Energy, Washington, D.C. from 1983 to 1984. Other imbibition. experience includes working on IGCP project Pan-African crustal evolution of the Nubian-Arabian shield at the They have been validated on simple fracture networks from Johannes Gutenberg-Universität, Mainz, Germany, 1982, reference fine-grid simulations with a conventional reservoir Tin Tungsten exploration in granitoid ring complexes, and simulator. Their efficiency to process actual complex Wellsite formation evaluation with Chevron Overseas. geological image is also demonstrated. Currently he is working on integrated reservoir characterization, structure and modeling. He is a member With such a methodology and linking software, the reservoir of the AGU, AAPG, GSA, and Sigma Xi. engineer can build a representative dual-porosity model from the geologic images resulting from field fracturing data. This Laura M. Ogden is the Data Mining Program Manager at optimal use of geological data will improve the reliability SAS Institute Dubai Branch office. She is responsible for of dual-porosity reservoir production forecasts. all data mining initiatives and provides consulting expertise to corporations throughout the Middle East. She has assisted

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Marie-Christine Cacas has nine hydrocarbon kitchens: to the east and southwest of the years experience as Research structure. Within the kitchen centers, generation and Engineer at the Institut Français du expulsion of oil began more than 250 million years ago, Pétrole. She received her PhD in wet gas/condensate by the start of the Cretaceous, and dry Hydrogeology from Ecole des Mines gas by the end of the Cretaceous. Early-formed structures de Paris. From 1989 to 1991 she were initially charged with oil, and have subsequently been developed a finite element code for partially to completely displaced by thermally mature gas/ the simulation of the dynamic condensate and, in areas proximal to the kitchen centers, behavior of flexible risers. Her dry gas. Although the gas/condensate reservoirs at Ghawar research deals with the analysis and have been filled for at least the last 100 million years, large the numerical modeling of naturally fractured reservoirs. geochemical variations still exist, even within individual Her areas of professional interest are stochastic and reservoirs. Significant amounts of hydrogen sulfide are only geomechanical modeling of fracture rocks. found in carbonate reservoirs of the Khuff Formation, and result from in situ thermochemical sulfate reduction in Bernard Bourbiaux (see abstract "Improved Modeling of deeper (hotter) parts of the reservoir. Carbon isotopic and Matrix-Fracture Transfer Simulators" on page 70 for gas chromatographic differences reflect slight differences biography and photograph) in the organic facies of the source rock, thermal maturity of the source rock during generation, and separate migration Sylvain Sarda is a Research pathways to the reservoir. The preservation of the Engineer in the Reservoir Modeling geochemical differences indicates the reservoirs are Group of Institut Français du Pétrole compartmentalized, i.e., they are divided into individual non- (IFP). He has been working on communicating sectors separated by permeability barriers. numerical methods for fractured Detailed geochemical characterization of the eastern Saudi reservoir simulation since 1995. Arabian gas/condensates has proven to be a very useful tool Before joining IFP in 1995, he was a to identify hydrocarbon migration pathways, determine Numerical Engineer of the services reservoir filling history, and evaluate the extent of fluid company CENERGYS for 4 years. communication within and between reservoirs. Sylvain holds a MSc degree in Physics from ENSI-ISMRa, Caen, France. William J. Carrigan has been with the R&D Laboratory of Saudi Aramco for the past eight years as a Geochemistry of Eastern Saudi Arabian Research Scientist. His areas of interest are basin evaluation, stable Paleozoic Gas/Condensates isotope geochemistry, and petroleum geochemistry. Prior to joining Saudi William J. Carrigan, Peter J. Jones, Aramco, William was with the Mark H. Tobey, Henry I. Halpern, Geological Survey of Canada and the Lawrence E. Wender, Saudi Aramco University of Ottawa, and specialized Richard Paul Philp and Jonathan Allen in stable isotope geochemistry and mineral geochemistry. University of Oklahoma He received a BSc in Geology from Queen's University and a PhD also in Geology from the University of Ottawa. Major reserves of gas and condensate are found in deep Paleozoic sandstone and carbonate reservoirs at Ghawar field Peter J. Jones is a Research Scientist in Eastern Saudi Arabia. These gas/condensates exhibit at Saudi Aramco's Research and distinct compositional and geochemical differences that Development Center. Prior to joining reflect (1) generation from different source rocks or facies Saudi Aramco in 1991, he worked in variations within a single source rock, (2) differences in exploration and production geology thermal maturity during generation and expulsion, (3) post- for Mustang Production, OKC (1982- generative in-reservoir hydrocarbon alteration processes, and 1986) and Union Pacific Resources (4) reservoir compartmentalization, or a combination of the Company, (1986-1991). Peter above. Correlation studies show that the gas/condensates received his BA degree in Earth were generated from the same source rock as the low sulfur, Sciences from Dartmouth College super light oils found in Paleozoic sandstone reservoirs in and a MSc degree in Geology from University of Oklahoma Central Saudi Arabia - the basal 'hot shale' of the Qusaiba (1986). His areas of interest include basin-wide thermal Member of the Silurian Qalibah Formation. Thermal maturity modeling, hydrocarbon migration timing/path maturity modeling of the Qusaiba shale in the vicinity of assessment, and reservoir geochemistry. the Ghawar structure indicates the presence of two main

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Mark H. Tobey is a Research Jonathan Allen received his BSc Scientist with the Lab R&D Center degree in Chemistry from the of Saudi Aramco. Prior to joining University of Science and Arts of Saudi Aramco, Mark worked with Oklahoma and attended graduate Exxon Chemical Company as a school at the University of Oklahoma Senior Analytical and Process Chemistry and Biochemistry Chemist. He received a PhD degree Department. After leaving graduate in Chemistry from Texas A&M school, he worked for an University. His current research environmental laboratory for a interests include oil fingerprinting couple of years. Since then he has and it applications to petroleum geochemistry. worked for Professor R.P. Philp at the University of Oklahoma Geology and Geophysics Department as a Henry I. Halpern is a Research Laboratory Equipment Technician assisting Professor Scientist with the Lab R&D Center Philp's REsearch Group with various petroleum and of Saudi Aramco. Henry worked with environmental research interests, sample analysis and Sohio between 1981 and 1985, with intrument maintenance. ARCO between 1985 and 1989, and with Shell between 1989 and 1992 prior to joining Saudi Aramco. He Geochemical Simulation of Dolomitization received a BSc degree in Chemistry from Lafayette College in 1977 and in Platform Carbonate Reservoirs a PhD degree in Organic Chemistry from the University of California, Los Angeles in 1981. His Emmanuel Caspard, Etienne P. Brosse, research interests include reservoir geochemistry. Frans S.P. van Buchem Institut Français du Pétrole Lawrence E. Wender is a Geological Gregor P. Eberli, University of Miami Consultant with the Area Exploration and Maurice Renard Department of Saudi Aramco. He Université Pierre et Marie Curie, France was previously with Mobil Oil Corporation and has nearly 20 years Dolomitization modifies and generally enhances the of oil industry experience. He is petrophysical properties (porosity and permeability) of currently involved in the study and carbonate reservoirs. Understanding the hydrological and exploration of the Paleozoic of Saudi geochemical mechanisms of this phenomenon allows for Arabia. Lawrence holds a MSc the quantification and prediction of the dolomitization degree in Geology from the process. We present a geochemical simulation model University of Utah. (DIAPHORE) which is tested on a dataset of Neogene deposits in the Bahamas. Richard Paul Philp is a Professor of Petroleum Geochemistry in the The stratigraphy and mineralogy of the carbonate platform School of Geology and Geophysics in the Bahamas has been studied in great detail (ODP Legs at the University of Oklahoma. He 101 and 166; RSMAS, University of Miami). This large received his BSc degree in Chemistry subsurface dataset permits the study of the dolomitization from the University of Aberdeen, process in a precise stratigraphical and diagenetical frame. Scotland and his PhD in Organic Isotopic data show that dolomitization took place in marine Chemistry in 1972 from the or marine-derived fluids, and is closely related to the University of Sydney, Australia. The hardgrounds. The “coupled reaction-transport” model major theme of his research is DIAPHORE, developed by the Institut Français du Pétrole, directed at the application of organic and analytical uses physico-chemical relations to describe the different chemistry to fossil fuel research, in particular the mechanisms of diagenesis and their interactions. It takes determination of compounds known as biomarkers found in into account numerous parameters such as kinetic constants oils and extracts of source rocks. He has also investigated for carbonate reactions, porosity, permeability, size and the application of pyrolysis gas chromatography and mass reactive surface of the grains, mineralogy, temperature and spectrometry, and gas chromatography-isotope ratio mass pressure, and the composition and velocity of fluids. spectrometry to various aspects of petroleum and reservoir geochemistry.

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After a study of the saturation state of interstitial fluids, tests of which one year was spent with Elf were conducted with DIAPHORE with various initial Aquitaine Production, and 6 years mineralogies, fluid composition, fluid-flow velocity and with the IFP. His specialization is the kinetic coefficients. These DIAPHORE simulations showed study of carbonate petroleum that: (a) aragonite dissolves quickly, which appears to be in systems, including both source rocks good agreement with field data; (b) aragonite dissolution is and reservoir facies. These studies controlled by kinetics, and not by the velocity of the fluid involve the combination of sequence flow; (c) dolomite precipitates in large amounts (upto 100% stratigraphy, sedimentology, organic of the mineralogical composition), which is again in and mineral geochemistry. Frans has agreement with field data: some recifal horizons appear a MSc in Geology and a MSc in entirely dolomitized; and (d) with some specifical fluid Biology from the University of Utrecht, Netherlands (1986), compositions, significant increase of both porosity (of about and a PhD in Geology from the University of Cambridge, 10%) and permeability is observed. The relationships UK (1990). between these two parameters was described by the Kozeny- Karman law. Other laws are also available and future work Gregor P. Eberli is Associate will consist in calibrating these with field data. However, Professor at the University of Miami, our data show evidence of a close relationship between where he is Head of the Comparative permeability and dolomite, with the highest permeabilities Sedimentology and Petrophysics associated with highest amounts of dolomite. Laboratories. His research projects focus on sedimentology and sequence In particular, the rate of dolomitization still remains a stratigraphy of carbonates and mixed problem. Our tests showed times ranging from 10000 years systems, and petrophysics of to 10 million years. This essential parameter needs to be carbonates. He received his PhD in investigated in more detail since it may elucidate the possible 1985 from the Swiss Institute of link between diagenesis and sea-level fluctuations. Technology, Zurich.

Emmanuel Caspard is a first year Maurice Renard is Professor at the PhD student at the Geology- University Pierre et Marie Curie of Geochemistry Division of the Institut Paris, where he is Head of the Français du Pétrole. He works on the Stratigraphy Department. His main integrated study of sequence field of research is the chemio- stratigraphy and diagenesis of stratigraphy with a special focus on carbonates (and most of all carbonate trace-elements and stable dolomitisation), and numerical isotopes. modeling of diagenetic processes. He received a MSc in Geology from the University Pierre et Marie Curie, France in 1997.

Etienne P. Brosse is a graduate from A New Production Logging Service for the Ecole des Mines et de la Multi-phase Horizontal Wells Métallurgie in Nancy (France). In 1982, he defended a PhD on the David Chace, Darryl Trcka geochemistry of black-shales. He Western Atlas Logging Services joined the Organic Geochemistry Olaf Bousché, Alex van der Speck Department in the Institut Français Shell International Exploration and Production BV du Pétrole (IFP) in 1983, where he Hassan A. Al-Nasser has been working on the source rocks Petroleum Development Oman of various basins including the former USSR, Iraq and Italy. Etienne was seconded to A new service specifically designed for production logging Total in 1990-1991 for a basin modeling study on the in multiphase horizontal or deviated oil producers is capable Mahakam basin. He then initiated and developed new of obtaining three phase flow rates in any flow regime, any research activity at IFP on the numerical modeling of watercut, and any gas volume fraction is presented. The mineral diagenesis in reservoirs. service combines interpretation of measurements from new downhole instrumentation and multiphase flow modeling. Frans S.P. van Buchem is Senior Research Scientist at the A new production logging instrument utilizes arrays of Geology-Geochemistry Division of Institut Français du capacitance sensors to make across-the-borehole Pétrole (IFP). He has 7 years experience in the oil industry, measurements of liquid level, hold up, and phase velocity

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while simultaneously making average borehole Unit A (> 50 meters thick) consists of very coarse channel measurements of pressure, temperature, diameter and noise. sandstone bodies interbedded with variegated silty claystone. The sample rate of measurements is such that variations in The sandstone bodies form continuous channel belts and velocity or hold up as they would occur in intermittent flow are interpreted as braided sand sheets. They are considered can be tracked. Flow loop data is presented that as the best reservoirs of the studied sequence. Unit B (0 to demonstrates the tool's capabilities under wide range of 15 meters thick) consists of a complex assemblage of facies conditions. A second instrument utilizes pulsed neutron developed along low-angle accretion surfaces and technology to measure average three-phase holdups across corresponds to an incised valley filled with a system of the wellbore. These instruments are combinable with coalescent argillaceous and sandy estuarine point bars conventional production logging tools and are conveyed on showing weak tidal influences. It shows a much more coiled tubing. complex reservoir geometry than the lower braided channels of Unit A. The valley fill of Unit B is capped by the The volume of data generated by this new service requires transgressive deposits of Unit C (3 meters thick) strict quality control and a means to enforce consistency corresponding to the basal Khuff Formation. These form a between the measured flow characteristics. Three stages of continuous tabular horizon of burrowed argillaceous quality control are defined. First, the redundancy in the sandstone showing a rapid vertical increase in marine fauna data is used to check if the instruments function is intended. and are interpreted as sheetflood deposits in a shallow lagoon Second, the relation between pressure drop, hold up and environment representing the last expression of the fluid velocity as captured by a multiphase flow model is landward-stepping fluvial system. As the transgression used to enforce consistency between these measured continued, storm/wave clastic beds occurred, interbedded quantities or to mark bad data. Third, log data can be with shallow marine carbonate of Unit D. This unit is of compared to previously generated simulated logs. great lateral extent and forms the seal of the Gharif reservoir.

David Chace, Darryl Trcka, Olaf Bousché, Alex van der The studied clastic Permian succession of Oman records an Spek and Hassan A. Al-Nasser (see abstract "Pre-Job overall transgressive trend punctuated by two Planning of Production Logs in Multi-phase Horizontal unconformities. The estuarine valley fill of Unit B is Wells: Multi-phase Flow Model Assisted Well Log separated from the braided fluvial deposits of Unit A by a Programming" on pages 70-72 for biographies and major unconformity expressed by a continuous erosion photographs) surface. The fluvial/estuarine deposits of Unit B are truncated by a transgressive ravinement surface at the base of the burrowed marine sandstone of Unit C. Sedimentology and Reservoir Geometry of the Upper Permian Upper Gharif and Philippe Crumeyrolle is Sedimentologist with Total Oil Lower Khuff Formations in Interior Oman: Company. He has 8 years of Outcrop Study in the Haushi Area experience and has worked on outcrop and subsurface case studies Philippe Crumeyrolle, Total CST in siliciclastics. His main activity Philippe Razin, Jack Roger, Jean-Pierre Platel Bureau consists of reservoir analysis and de Recherches Géologiques et Minières modeling. Philippe received his PhD and Jean Broutin, Universitè Pierre et Marie Curie from the University of Bordeaux in 1987. He is member of the French The Upper Gharif and Lower Khuff formations have been NDP Association. studied in outcrop in order to describe and understand the facies, geometry and stratigraphic pattern of the Upper Philippe Razin received his PhD in Permian transgressive succession of Oman. The studied Sedimentology and Tectonics from outcrop on the western flank of the Huqf Anticline in the the University of Bordeaux in 1989. Haushi area is an analogue to the Gharif oil-bearing His research deals with tectonics and reservoirs farther west in the neighboring Central Oman Salt sedimentation relationships in the Basin. The aim of this study is to reconstruct and understand Pyrenees mountain belt during the architecture and internal heterogeneities of reservoirs in Mesozoic and Cenozoic times. He the vicinity of producing fields. The Upper Gharif and Lower joined the Bureau de Recherches Khuff formations comprise four main successive Gèologiques et Minières in 1990. lithological/geometrical units, informally called Units A, B, Philippe is involved in basin analysis C and D. They correspond to the four main depositional projects in Peritethys areas, mainly France, Morocco and systems of the Late Permian major transgressive event. the Arabian Peninsula (Paleozoic and Cretaceous of Saudi Arabia; Permian, Cretaceous and Tertiary of Oman). He is a member of the French Association of Sedimentology.

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Jack Roger joined the Bureau de Based on detailed studies of outcrops, we first review the Recherches Géologiques et Minières different types of fracture swarms. A particular emphasis in 1976. He has been involved in will be laid on the foredeep of the Northern Oman Mountains many geological mapping projects in where beautiful 3-D outcrops can be compared to carbonate Saudi Arabia and Oman, focusing on reservoirs in the subsurface. We first demonstrate how the stratigraphic and sedimentologic measurements along scanlines, which give the same aspects of Mesozoic and Cenozoic information than image logs, can be used to distinguish the units. Jack graduated from Orsay different types of fracture swarms. We show that the study University. He is affiliated with the of systematic joint sets and normal faults, cutting the top of French Geological Society and the antiforms, help predict some of the geometrical attributes French and International Associations of Sedimentologists. of these swarms, such as direction and length. When applied to reservoir characterization, this means that 3-D seismic Jean-Pierre Platel has been with the can be used as a first approximation, however, horizontal Bureau de Recherches Géologiques wells are required for full descriptions. et Minières since 1975. He is an experienced mapping Geologist, Using the Institut Français du Pétrole fracture modeling involved in the mapping of the software FRACA, we investigate the influence of the Mesozoic of Aquitaine-France and of characteristics of fracture swarms on fluid flow. We show Meso-Cenozoic of Oman. He that both the geometry of the swarms and the characteristics received his PhD from Bordeaux of the underlying systematic fracture sets has to be taken University. He is a member of the into account to improve fractured reservoir management. French Geological Society and of the French Stratigraphical Committee. Mainly because of the characteristic length scale of the fluid flow associated with fracture swarms, our results identify Jean Broutin is Professor of some issues which concern fluid simulation in fractured Paleobotany and Paleoecology at the reservoir. These issues are addressed in the conclusion. University of Paris. He received his Doctoral Thesis from Paris Jean-Marc Daniel has three years University. Jean is a Specialist of experience as Research Engineer at Late Paleozoic micro and the Institut Français du Pétrole. macroflora. He is involved in a Jean-Marc received his PhD in research program focusing on the Geosciences from Pierre et Marie western part of the Tethys (Morocco, Curie University. While preparing his Spain, France, Italy and Arabian PhD Thesis in the Laboratory of Peninsula). Geology of the Ecole Normale Superieure in Paris, he studied the formation of the Tyrrhenian Basin (Western Mediterranean Sea) using structural data and Fracture Swarms in Fractured geomechanical models. During this period he taught Reservoirs: Characterization, Modeling Geology and Geophysics at the Villetaneuse University. His and Influence on Fluid Flow main interests are numerical and analogue modeling of fractured reservoir and structural analysis of fractured rocks Jean-Marc Daniel and Marie-Christine Cacas on outcrops. He is presently developing new methodologies Institut Français du Pétrole for multi-scaled mapping of fracture networks and advanced integrated studies of fractured reservoir. The increasing number of horizontal wells, where image logs and flowmeter profiles are available, has deeply Marie-Christine Cacas (see abstract "How to Turn the improved the description of fluid flow in fractured reservoirs. Geological Image of a Fractured Reservoir into a Dual- In many of these reservoirs, only small intervals account Porosity Model" on page 79 for biography and photograph) for the main part of the production. These intervals frequently correspond to highly-fractured zones, that in some cases, are responsible for early water breakthrough. Therefore, any understanding of the geometry and genesis of these fractured zones, together with an analysis of their dynamic properties, can improve the models of fluid flow within fractured reservoir.

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Open Hole Log Limitations and its Multi-Disciplinary Reservoir Implication in Testing Decision Characterization of Khuff-C Gas Reservoir in 'Uthmaniyah Area of Abdel Rahman R. Darwish, Ali M. Al-Amoudi Ghawar Field, Saudi Arabia and Burhan M. Irshaid Abu Dhabi National Oil Company Shiv N. Dasgupta and Ming-Ren Hong Saudi Aramco When arriving at a decision to test a potential hydrocarbon- bearing reservoir in an exploratory or appraisal well, several Integration of recently acquired 3-D seismic data with factors must be considered. These include hydrocarbon borehole information and reservoir simulation history match shows, descriptions of cores and ditch samples, drilling results has redefined the stratigraphy in the Permian Khuff- problems and, most importantly, open hole log C gas reservoir over central ‘Uthmaniyah field in Ghawar. interpretations. In some wells these factors may result in Amplitude inversion of the 3-D seismic data shows localized conflicting evidence or contradictory interpretations. This high acoustic impedance near the crest of Khuff structure renders the testing decision very restrictive and could result which is interpreted as “an island” of tight Khuff-C reservoir. in a new hydrocarbon-bearing zone being missed. Today On the structural flanks low acoustic impedance values, logs are acquired at high costs and with advanced tools and corresponding to porous, gas-saturated reservoir, were techniques; they are considered the primary factor in derived from . Based on these results, the determining whether to test a zone. Several case studies previously interpreted stratigraphic porosity edge to the east are shown here which are based on the interpretation of open flank in the Khuff-C reservoir has been revised. This could hole logs. The cases show both examples where negative add upto 25% to the delineated gas and condensate reserves and encouraging log indications correspond with in the Khuff-C reservoir. hydrocarbon-bearing tests. The paper also provides the reasons for these contradictory results so that they can be The Khuff-C reservoir in Ghawar field falls within a avoided in the future. sequence of cyclic carbonate-evaporite deposits of the Permian Khuff Formation. The reservoir interval is Abdel Rahman R. Darwish is a comprised of interbedded, tight and porous limestone and Senior Geologist with Abu Dhabi dolomite sandwiched between thicker anhydrite-rich National Oil Company (ADNOC) in intervals. Syndepositional stratiform diagenetic changes the Exploration Division. Prior to influenced by the depositional environment, were joining ADNOC in 1980, Abdel responsible for Khuff-C reservoir porosity. Several wells in Rahman worked with the National the north-central field area penetrated the Khuff-C reservoir. Oil Corporation in Libya between Two of these wells encountered tight Khuff-C reservoir 1975 and 1980. He received a BSc interval. Cores from the Khuff-C in these wells show in Geology from Cairo University in anhydrite cement filling the grainstone matrix and layers of 1974. Abdel Rahman is a member of fine-grained dolomite. From these results, a stratigraphic the SEE. zero-porosity edge was originally interpreted to the east of these two wells and the eastern flank of the Khuff structure Ali M. Al-Amoudi is Senior was condemned for further Khuff-C reservoir development. Geologist with Abu Dhabi National Reservoir simulation history match results, however, suggest Oil Company. He has 17 years extra sources of Khuff-C reservoir energy in the eastern experience in the field of Exploration flank. Additional 700-800 pounds per square inch reservoir Geology in the United Arab Emirates. pressure was computed in the model wells to the east. This Ali received a BSc in Geology from can only be explained with more pore volume, larger reserves Cairo University in 1979 and is a and water invasion from the aquifer. member of the SEE and SPE. The 3-D seismic data in the area show an abrupt termination of amplitude corresponding to the Khuff-C reservoir near Burhan M. Irshaid received his MSc these two tight wells. Model-based seismic amplitude degree in Petroleum Geology from inverse modeling was performed on the data. The amplitude Karachi University in 1970. Burhan inversion was target-oriented, iterative and was constrained worked with Sonatrach for 8 years by acoustic impedance computed from the sonic and density as a Well-Site Geologist. In 1979 he logs at the wells. The results indicate an increase in acoustic joined Abu Dhabi National Oil impedance from known, porous, gas-filled, Khuff-C Company as Senior Operation reservoir to tight Khuff-C. The higher acoustic impedance Geologist and since 1985 has been is interpreted as a tight Khuff-C interval and is seen as an working as Senior Reservoir Geologist. 84

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island with tight porosity localized at the crest of Khuff 3-D Seismic Coherency Attributes for structure. The sharp waveform contrast of amplitude peak associated with porous Khuff-C and the diminishing Improved Imaging of Subtle Faults amplitude, or in some cases, reversal of polarity from peak and Stratigraphic Features to trough for non-porous reservoir, provided a basis for delineating the Khuff-C reservoir using 3-D seismic data. Shiv N. Dasgupta, Christian J. Heine Post-inversion analyses include layering of the acoustic and Thomas T. Hu impedance volume computed from the seismic data and Saudi Aramco transforming them to reservoir properties such as porosity and fluid saturation. The results of seismic amplitude Coherency attributes computed from 3-D seismic data in inversion indicate that the Khuff-C porosity extends to the field areas of Saudi Arabia have demonstrated a significant entire eastern flank of the ‘Uthmaniyah field and thus opens impact on subsurface imaging and have enhanced the quality up a large fairway for porous Khuff-C reservoir delineation. of seismic interpretation. The coherency technique improves the imaging of geologic features in 3-D seismic data that Shiv N. Dasgupta is currently are at sub-seismic resolution. Subtle features like fracture Geophysical Consultant with Saudi swarms, minor faults, and stratigraphic features like channel Aramco. He worked with Continental sands can be mapped by augmenting the conventional 3-D Oil Co. Oklahoma (1974-1976), Seis- seismic data with coherency attributes. mograph Service Corporation, Tulsa (1976-1977) and Amoco Production Coherency is a post-stack statistical process that computes Company in Tulsa and Houston (1977- similarity or dissimilarity between neighboring seismic 1982) prior to joining Saudi Aramco traces in a 3-D data volume. The amplitude data is in 1982. He received a BSc degree transformed into a volume of coherency attributes where in Geophysical Engineering from the continuous reflectors show high coherency, while reflectors Indian School of Mines in 1971, a MSc degree in Geophysics that are locally disrupted due to stratigraphic features like from St. Louis University in 1973 and MBA from Southern porosity edges or faults, show low coherency values. Three- Illinois University in 1975. Shiv also completed graduate dimensional visualization of coherency attributes has created studies in Petroleum Engineering from the University of a new paradigm in the interpretation of subtle geological Houston in 1981. He is a member of the AAPG, SEG, EAGE, features. Images of time slices and 3-D cube displays of SPE and the AGU. His professional interests include multi- conventional seismic amplitude data are compared with disciplinary reservoir characterization, application of new the identical data with coherency enhancements. technology for improved subsurface definition and computer application and database interconnectivity. Shiv N. Dasgupta (see abstract "Multi-Disciplinary Reservoir Characterization of Khuff-C Gas Reservoir in Ming-Ren Hong is currently 'Uthmaniyah Area of Ghawar Field, Saudi Arabia" on this Geophysical Specialist with Saudi page for biography and photograph) Aramco. Prior to joining Saudi Aramco he worked with the Center Christian J. Heine received his MSc for Lithospheric Studies, University in Geology from the University of of Texas at Dallas as Research Tennessee in 1982 and a MSc in Engineer (1982-1984) and Arco Oil Petroleum Engineering from Tulane and Gas Co. as Senior Research University in 1990. Christian was Geophysicist (1984-1991). Ming Associate Professor at Tulane holds a BSc degree in Atmospheric University from 1990 to 1991, and Physics (1973) and a MSc degree in Geophysics (1977) from worked with Mobil Oil from 1982 to the National Central University, Taiwan. He received his 1990. He joined Saudi Aramco in PhD in Geophysics from the University of Texas in 1982. 1991. Christian is a member of the Ming is a member of the SEG and SPE. His professional AAPG and DGS. interests include seismic modeling and inversion, reservoir characterization and integrated interpretation.

GEO’98: Short Course No. 1 Geostatistics in Petroleum Geology 19 April, 1998 For more information please contact: Arabian Exhibition Management WLL, P.O.Box 20200, Manama, Bahrain Tel: (973) 550-033; Fax: (973) 553-288; e-mail: [email protected]

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Thomas T. Hu received his BSc effects seen on the longer offsets. The use of coherency degree in Electrical Engineering technology in the pre-stack data creates an interesting from the National Taiwan University opportunity in the area of amplitude versus offset analysis. in 1973, and MSc and PhD degrees For example, the coherency technique can be used to also in Electrical Engineering in establish the gradient changes of the seismic waveform 1978 and 1981, from the University across the recorded offsets. Calibrating this response across of Houston. Prior to joining Saudi a known anomaly, such as a gas-oil contact, can be used as Aramco, Thomas worked with the diagnostic seismic fingerprint to search for similar Geophysical Systems Corporation, anomalies. This has a major advantage over conventional Geophysical Development amplitude versus offset studies as it is based on waveform Corporation, Marathon Oil Company and Texaco. Thomas response rather than on amplitude alone. is affiliated with Sigma Xi, the IEEE and SEG. His research interests are seismic data visualization and digital signal Shiv N. Dasgupta (see abstract "Multi-Disciplinary processing. Reservoir Characterization of Khuff-C Gas Reservoir in 'Uthmaniyah Area of Ghawar Field, Saudi Arabia" on page 85 for biography and photograph) Application of Coherency Technique Vasudhaven Sudhakar is President on 3-D Seismic Data of Coherence Technology Co. Pulsonic in Canada and is also the Shiv N. Dasgupta, Saudi Aramco co-founder of Coherence Technology Vasudhaven Sudhakar and Anthony J. Rebec Company based in Houston, Texas. Coherence Technology Co. He received his BSc degree in Physics from Madras University, India in Application of 3-D seismic coherency has provided 1979. Vasudhaven has over 17 years improved understanding of structural and stratigraphic experience as a Professional details of the subsurface, leading to revised 3-D geologic Geophysicist in the seismic models. Presented here is a description of the Coherency contracting business, seismic data processing and design, Cube methodology and various new applications with results with over 15 years experience in 3-D seismic. From 1990 from Saudi Aramco fields. It is intended as both an to 1993 he worked in the R&D Department for introduction to the technology, and to demonstrate the power Geophysical Service. Starting his career in 1980 he has of its use as a complementary 3-D volume to the worked for Geophysical Service Inc., Halliburton conventional 3-D seismic volume for 3-D seismic Geophysical Services Inc. and Energy Innovations. interpretation. This technology reveals important geologic information that may be totally overlooked using Anthony (Tony) J. Rebec is conventional processing. Technical Marketing Manager for Coherence Technology Company The ability to measure three-dimensional spatial variations based in Houston, Texas. He received in the seismic waveform, with dip and azimuth his BSc degree in Geology and comprehension, is an extremely powerful capability. The Mathematics from London University basic seismic waveform contains a measure of time, in 1967. Tony has over 30 years frequency, amplitude and absorption quantities. These vary experience in data acquisition and spatially as the recorded seismic responds to lateral design, processing and interpretation variations in the physical and geometric properties and of which 20 years were directly lithologic facies. Measuring these combined changes in the associated with 3-D seismic. His last 10 years have been seismic response allows the interpreter to map these changes involved with integration and exploitation of 3-D seismic if recorded by the seismic technique. The seismic coherency data leading to reservoir characterization. Starting his measurement, as applied here, is an attempt to capture these career in 1967 he has worked for Geophysical Service Inc., changes. This coherency response can be decomposed into Halliburton Geophysical Services Inc. and Western various attributes in order to identify the components that Geophysical. He is a 30-year member of the SEG and has are changing. delivered numerous presentations on various aspects of 3- D reservoir geophysics and interpretation. Tony has a broad The application of coherency to pre-stack seismic data, to base with global experience, including Africa and the Middle optimize the imaging of faults and fractures by selective East, Far East, North Sea and Australia. He is a member of offset contributions based on coherency is presented. The the SEG, EAEG and the PESGB. coherency technique can also be used to separate the imaging of structural effects on the shorter offsets from the pore fluid

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3-D Seismic Porosity Modeling in a Philippe M. Doyen received a Masters degree in Mining Shu'aiba Oil Reservoir Using a Engineering from the University of New Form of Cokriging Louvain, Belgium, in 1982, a MSc in Geophysics from Stanford University Lennert D. den Boer, Philippe M. Doyen in 1984, and a PhD in Geophysics Western Atlas International from Stanford University in 1987. and Heinrich W. Rothenhoefer Upon graduation he joined Western Petroleum Development Oman Geophysical in Houston, as a Research Geophysicist. In December In recent years, there has been considerable interest in the 1989, Philippe was transferred to Western in London where general problem of integrating seismic data in reservoir he is currently managing the Reservoir Characterization modeling applications. The geostatistical approach of R&D Department. cokriging has been of particular interest owing to its flexibility, in that it accounts for the statistical cross- Heinrich W. Rothenhoefer received correlation between a seismic attribute, seen as a secondary a PhD degree in Geology from the variable, and a primary variable to be mapped such as University of Erlangen, Germany, in porosity. However, cokriging is still perceived as a difficult 1984. In the same year he joined technique, since its conventional implementation requires BEB, a Shell/Exxon company, in identification of spatial cross-covariance functions and Hannover, Germany, as a Reservoir solving a system of normal equations more complex than Geologist. Heinrich worked as Head kriging. Here, we use a new form of collocated cokriging, of Production Geology in an equity based on a Bayesian updating of the kriging solution, which team from 1989 to 1990, and as requires neither explicit reference to cross-covariance Section Head of Reservoir Geology functions nor solving a cokriging system. With this new & Operations from 1990 to 1991. Between 1991 and 1994, implementation, cokriging predictions can be directly he was assigned as technical adviser to an arbitration team. computed from kriging estimates in a very efficient manner. Since 1995, Heinrich has been working on several Shu'aiba This is particularly useful for large 3-D grids, when studying oil fields in Central Oman. the sensitivity of cokriging results to the degree of correlation between the primary and secondary variables.

The new form of collocated cokriging is applied to estimate Reservoir Quality and Water Cut the 3-D distribution of porosity and permeability within a Potential Using the CMR Derived tight carbonate oil reservoir in the Shu'aiba Formation in Nuclear Magnetic Measurements Oman. An acoustic impedance volume, obtained by inverting a 3-D seismic dataset, is used to guide the kriged porosity Robert Dennis, Schlumberger Overseas (Muscat) estimates away from the available well locations, based on and Austin Boyd, Schlumberger Overseas (Dubai) the strong negative correlation between porosity and impedance. Porosity is then used to constrain the kriged The Lower-Middle Cretaceous limestones in the Middle permeability, according to the strong relationship between East, are being developed with both vertical and horizontal them. The impact of the seismic data and the sensitivity of wells. The main reservoirs in the region vary from the estimates to the seismic constraint is then assessed in a packstones to mudstones with associated textural and grain dynamic manner. size variations through the vertical sequence. These variations control reservoir quality and saturations that make Lennert D. den Boer is a Research it difficult for engineers or geologists to select the best Geoscientist at Western Atlas reservoir sections. Some of the most important oil and gas International. He received a BSc structures contain fine-grained wackestones with high degree in Geophysics from the irreducible water saturations that cause of the low resistivity University of British Columbia, values of 1.5 ohm-m that are recorded in the hydrocarbon Canada, in 1983. On graduation he zone. joined Western Geophysical in Calgary, Alberta, as a Special To account for this, new logging programs have been Projects Geophysicist. In 1990 he was implemented and integrated with the available core data. transferred to London to join the The new approach involved adding the Combinable Reservoir Characterization R&D Department, where he Magnetic Resonance (CMR) and Modular Formation helped develop the SigmaView geostatistical system. Lennert Testing (MFT) (dual packer) tools to the conventional suite is currently involved in R&D for the EarthGM 3-D system of logging tools. The CMR tool was used to predict water and associated reservoir characterization projects.

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cut potential and reservoir quality. The permeability results Technique and Technology of Deviated from the CMR tool’s pore size analysis were calibrated with the MDT tool’s dual packer drawdown permeability and and Horizontal Wells Survey applied for a continuous measurement. This calibration has Using Special Cable since been validated using core data and confirmed using the MDT tool and core from four additional CMR wells. Rasim N. Diyashev, Renat K. Muslimov The Timur permeability equation, using the bound fluid and Arnold G. Korzhenevskiy volume from the CMR tool’s fast logging pass, was TatNIPIneft Institute, Russia examined and validated. Geophysical and hydrodynamic survey of deviated and The potential for water production in these fine-grained horizontal wells (inclination angles 65° and more) presents reservoir rocks is determined by comparing the bulk volume an urgent and sophisticated problem. water (BVW) from the resistivity with the irreducible bound volume (Bvirr ) from the CMR. These techniques are World practice for delivery of geophysical tools at the discussed and validated examples are illustrated. bottom-hole of such wells involves technology based on application of flexible pipes which contain a geophysical Robert Dennis (Bob) is the Division cable. In Russia such technologies as "Gorizontal 1-5", hard- Petrophysicist for Schlumberger and software-complex "Gorizont", which are rather Wireline of Oman and Pakistan and cumbersome and time consuming, have found wide is currently based in Muscat, Oman. application. He is responsible for developing applications for new petrophysical The firm "Neutron" has developed a special geophysical measurements and is currently cable which provides for running in of tools into a horizontal focusing on nuclear magnetic wellbore. With the aid of this cable and using production- resonance interpretation. Since type equipment, geophysical surveys can be performed in joining Schlumberger of Canada as horizontal wellbores of length upto 300 meters, and in the a Field Engineer in 1974, he has held several positions in case of applying of special procedures, in wellbores of length Marketing, Interpretation Development in North America upto 450 meters or more, both in cased and in openholes in along with two years at Schlumberger-Doll Research, carbonate rocks. Time expenses for geophysical surveys Ridgefield, Connecticut. Before coming to Oman, Bob was are considerably reduced and become commensurate with project leader for facies mapping and fracture evaluation the time consumed for surveys of vertical wells of studies in the Joint Research Center of Schlumberger and corresponding lengths. the National Oil Company in India in New Delhi. He earned a BSc degree in Electrical Engineering from the University The application of cable technology increases the array of of Saskatchewan, Canada in 1973 and is a member of geophysical methods for surveying horizontal wells. These SPWLA, SPE and NACE as well as contributor to their include Nuclear Magnetic Resonance methods, publications. Bob is also member of the APEGGA in Alberta, investigations through tubing using small size tools, jet-type Canada. perforating and other techniques for drilling and operating wells. Austin Boyd is Chief Petrophysicist for Schlumberger’s Middle East Unit According to the results of the survey, both conventional based in Dubai. He is responsible for filtration parameters of formations and composition of rocks, the technical support, the and their fluid saturation, are determined. introduction of new services and developing new interpretation Cable design and technology for carrying out surveys in techniques. Prior to moving to Dubai horizontal wells are protected by RF patent. Using this cable he was Product Development JSC "Tatneftegeophysica" has carried out surveys of more Engineer in the Magnetic Resonance than 100 horizontal wells for Russian oil companies like Department at the Schlumberger Tatneft, Udmurtneft and Samaraneftegas. Results of these Product Center in Houston. Austin joined Schlumberger in tests will be discussed. 1981 as a Field Engineer. He is a member of the SPE and SPWLA. He graduated in 1981 from Technical University Rasim N. Diyashev is currently Deputy Director of of Nova Scotia with a BSc in Electrical Engineering. TatNIPIneft and Chairman of the Geology and Development Section and a member of the Scientific Council with TatNIPIneft Institute. He has been Head and member of

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several commissions on examinations geophizika as Head of the of the state of development of giant Department of Field Geophysics oil fields. His interests include the between 1977 and 1985 and later as study and development of multi-layer Chief Engineer. He holds a PhD oil fields with complicated geological degree in Technical Sciences from Oil structures and complex development and Gas State Academy in Moscow. of heavy oils and bitumen reserves, His scientific interests are downhole including geology, production and logging - logging of vertical, deviated refining. Rasim is currently and horizontal wells in the process investigating consequences of of their drilling and operation. He flooding of heterogeneous reservoirs at the micro level. He has published more than 67 papers on this subjects and 17 is a Professor at Bashkortstan State University and a inventions. Arnold has been awarded bronze and silver member of the Russian Academy of Natural Sciences. He is medals for Exhibition of Economic Achievements and a a member of the SPE, AAPG and Vice President of the badge for Outstanding Oilman of USSR. International Consulting Company on Oil and Gas. He is the author of 200 published works and manuscripts including monographs, thematic reviews, text books and about 40 inventions. Rasim is an Honored Scientist of the Republic Stratigraphy of the Lower Paleozoic of Tatarstan and Russia and an I.M. Gubkin Prize winner. Haima Supergroup of Oman

Renat K. Muslimov is currently a Henk H.J. Droste Professor at Kazan State University. Petroleum Development Oman He has nearly 40 years of experience in oil exploration, oil field geology, Following the discovery of significant gas/condensate improvement of the processes of oil reserves in Lower Paleozoic clastics in Central Oman a fields development, application of the regional geological review using all available well data and advanced methods of monitoring and a set of regional seismic lines was carried out by Petroleum control of deposits depletion, Development Oman. The objective of this study was to application of secondary and tertiary support further appraisal and exploration activities. A enhancement oil recovery methods, chronostratigraphic framework of regional correlatable increase of efficiency of production of hard recoverable oil major flooding surfaces improved the understanding of the reserves and recovery of natural bitumens. Renat is a stratigraphic relationship between the different units and the member of the Development Section and Drilling Expert regional distribution of the reservoir seal pairs. The interval Council of Russia's Ministry of Fuel and Energy, member of interest, the Cambrian to Lower Silurian Haima of south-Ural Department of the Academy of Mining Supergroup, is a late syn- to post-rift siliciclastic infill of an Sciences of Russia, member of Scientific Council of the extensive graben system. The depositional setting was Department of Nuclear Physics of the Russian Academy of initially continental but higher in the sequence of marine Natural Sciences, member of the Academy of Mining deltaic setting prevailed. The sequence is characterized by Sciences of Russian Federation, Academy of Mineral the occurrence of laterally extensive sand sheets typical of Sciences and Academy of Sciences of the Republic of pre-vegetational times but difficult to interpret Tatarstan and an honorary member of Houston Geological sedimentologically. At least six major transgressive Society. Renat is also a member of the editorial board of regressive cycles can be recognized which can be regionally "Neftyanoye khozyajstvo" journal. He is the author of more correlated. Marine intercalations are limited to Central and than 400 published papers, more than 20 monographs and North Oman. The clastic influx into the grabens was initially more than 100 inventions. For outstanding contribution to of local origin but as the grabens filled up the sediments the oil industry in his country and the Republic, Renat has were predominantly derived from a southern source. been awarded the Academician Gubkin Prize (1982), Ministry of Oil and Gas Industry of the USSR Prize (1989 Henk H.J. Droste (see abstract "The Sedimentology of the and 1991), State Prize of the Republic of Tatarstan (1994) Haima Supergroup, Oman: Outcrop Study in the Huqf and Government of Russian Federation (1996). Region" on page 76 for biography and photograph)

Arnold G. Korzhenevskiy graduated as Geophysicist from Editor's Note: The above paper was published in GeoArabia Petroleum Technical School in Oktyabrskiy in 1959. Arnold in Volume 2, Number 4, December 1997, pages 419-472. worked as Chief Engineer at Bugulminsky Field Geophysical Enterprise between 1968 and 1977. He joined Tatnefte-

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Adverse Changes in the Response of an Effect of Both Formation Water Areal Geophone Array Caused by and Hydrocarbon Fluid Saturation Commonly Occurring Perturbations on Acoustics of Reservoir Rocks in Phone Positions Abdel Moktader A. El Sayed Mark S. Egan Ain Shams University, Egypt Geco-Prakla / Schlumberger Mahmoud H. El Batanony and Ahmed Salah Egyptian Petroleum Research Institute Geophone array patterns are designed for the purpose of suppressing ground roll. If phones are not planted in the Twenty-eight carbonate and sandstone core samples have exact locations prescribed by a given design, the nature of been obtained from the Upper Cretaceous Abu Rawash and the suppression is changed from that intended. This study Bahariya formations encountered in a drilled well in the examined the negative aspects of that change. northern part of the Egyptian Western Desert. They were subjected to complete petrophysical investigations including The reference array used in the analysis was composed of porosity, permeability, wettability, capillarity, and pore size 72 elements and measured 50 by 50 meters. The magnitudes distribution. of the phone position errors were distributed in a Gaussian fashion. Several experiments - with different standard Comprehensive Compressional (Vp) and Shear (Vs) wave deviations - were considered. The azimuths of the errors velocities were measured in the samples using ultrasonic were distributed uniformly throughout 360 degrees. An wave propagation. Saturation levels included: (1) ensemble response of all the receiver arrays contributing to completely dry; (2) partially-saturated with formation water a Common Depth Point stacked trace was computed for levels at 35%, 50% and 70%; and (3) fully saturated with each experiment. Each such response was then compared water and/or crude oil. Robust and reliable relationships with the envelope of the ideal response. were obtained and these can be applied in either exploration or production. The relationships between fluid saturation When the small amount of mispositioning caused by human and both Vp and Vs indicate a strong correlation. The error was modeled, it was found that the degradation to the relationship between Poisson's Ratio and fluid saturation ensemble response was negligible for spatial wavelengths can be used to detect hydrocarbon-bearing rocks and to trace greater than 16 m. For wavelengths shorter than that, the oil/water contacts. degradation occurred only at one azimuth - and that azimuth was oblique to the in-line and crossline directions. Abdel Moktader A. El Sayed received his BSc (Honors) degree in When receiver positions were perturbed a bit further - as Geology in 1972, MSc degree in would be the case when trying to avoid placing phones in Petrophysics in 1976 from Ain Shams vegetation, deterioration was noticeable only at wavelengths University and PhD in Petroleum shorter than 20 meters - and even then, the deterioration Geology from the Hungarian occurred at only two oblique azimuths. Academy of Sciences in 1981. Abdel Moktader was Assistant Lecturer Discussions in the full text conclude that phone positioning between 1972 and 1977, and errors of the magnitude typically witnessed today while Associate Professor of Petroleum acquiring data in Middle East desert environments do not Geology and Reservoir Geophysics between 1988 and 1994 endanger the integrity of the final processed product. at Ain Shams University. He was seconded to Qatar University as Lecturer and Associate Professor of Petroleum Mark S. Egan is the Middle East/ Geology between 1985 and 1989. He is currently a Professor North Africa Division Geophysicist in Reservoir Geophysics and Petroleum Geology at Ain for Geco-Prakla / Schlumberger, Shams University. Abdel Moktader is a member of the stationed in Dubai. Prior to this AAPG, Egyptian Geological Society, Egyptian Geophysical assignment, he worked for 5 years as Society, Egyptian Petroleum Exploration, Egyptian the Area Geophysicist in Dhahran, Sedimentary Society and the Hungarian Geophysical and prior to that he was in Houston Society. where he started in 1975. Mark holds a PhD in Geophysics, an MSc in Mahmoud H. El Batanony is currently Head of the Acoustics and a BSc in Physics. He Production Department at the Egyptian Petroleum Research is a member of the SEG, EAGE and SPE. Institute (EPRI). He received BSc and MSc degrees in Petroleum Engineering from Cairo University in 1971 and 1976. Mahmoud acquired a PhD in Petroleum Engineering

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from AZI Institute, USSR in 1982. He trap. The oil-productive Unayzah sandstone is imaged as a worked as Research Assistant in the high-amplitude reflection in an isolated area of Petroleum Unit with the National approximately 8 square kilometers. Research Center between 1972 and 1976 and as Assistant Teacher in the Seismic isochron maps are proving effective in identifying Oil Production and Petrophysics additional areas of stratigraphic potential in the region. Laboratories at AZI Petroleum. Upper Unayzah sandstones are present in the paleo-structural Mahmoud had also worked part-time lows (isochron thicks) and are absent on the paleo-highs as Consultant Engineer with Bapetco (isochron thins) due to both non-deposition and erosion. Oil Company and as Petroleum Engineer with Gulf of Suez Petroleum Company. He is a Daniel S. Evans is currently member of the SPE of AIME, Production Committee in Geological Specialist in the Central EGPC, Production and Exploration Committee in ASRT, Area Exploration Division of Saudi EPRI Board and Applied Research Committee at the Aramco developing prospects along Ministry of Scientific Research and Technology. the recently discovered Hawtah Trend in Central Arabia. Dan worked as a Ahmed Salah received his BSc Groundwater Geologist between degree in Geology from Ain Shams 1970 and 1975 and joined Aramco University, Cairo. Ahmed also holds in 1975 where he worked on a variety a Diploma in Petroleum Geology of assignments for the Exploration (1994) from Cairo University. He is Department until 1981. He then joined Tenneco Oil Co. as currently working with the Egyptian an Exploration Geologist from 1981 to 1984. Between 1984 Petroleum Research Institute (EPRI) and 1989, he worked for an independent oil operator based as Advanced Rock Properties in San Antonio, Texas. He rejoined Saudi Aramco in 1989. Laboratory Supervisor. Prior to his Dan holds BA and MA degrees in Geology from the employment with EPRI, Ahmed University of Texas at Austin. worked as Micropaleontologist with the Geological Museum in Cairo, as Field Geologist with the Geological Survey of Bassam H. Bahabri is currently the Egypt, as Core Analyst with NL Erco, and as Laboratories Chief Explorationist of the Central Supervisor with Core Laboratories, Egypt. Area Exploration Division of Saudi Aramco. For the last 16 years, Bassam has been involved in several Recent Discovery Confirms Stratigraphic geological and exploration projects. As part of his career development, he Trap Potential in the Permian Unayzah participated in exploration Formation of Central Saudi Arabia assignments with Exxon, Texaco and Chevron. Bassam graduated with a Daniel S. Evans, Bassam H. Bahabri BSc in Geology from King Saud University in Riyadh in and Ahmed M. Al-Otaibi 1981. He also obtained his DIC/MSc from Imperial College Saudi Aramco in Petroleum Exploration in 1993.

A recent discovery in Central Saudi Arabia of Arabian Super Ahmed M. Al-Otaibi received a BSc Light oil confirms stratigraphic trap potential in the Early degree in Engineering Geology from Permian Unayzah Formation and demonstrates another King Abdulaziz University in Jeddah successful application of 3-D seismic in the region. Located in 1990 and a MSc in Geology from about 175 kilometers south of Riyadh, the Usaylah-1 Keele University, UK in 1993. Ahmed discovery well targeted the updip pinch-out of the Unayzah has been working on various projects clastic section on the east flank of the Hawtah structural including reservoir characterization, trend. The seal is the basal shales and siltstones of the Khuff geostatistical reservoir modeling and and Unayzah formations and the source rock is the Lower exploration since he joined Saudi Silurian Qusaiba Shale. Aramco in 1990. He is currently a member of the Stratigraphic Trap Exploration Team, Central The well encountered an oil column of 31 feet in an upper Saudi Arabia. Unayzah eolian dune facies. The areal distribution of the productive sand had been mapped with a 3-D seismic survey Editor's Note: The above paper was published in GeoArabia prior to drilling the well. Seismic horizon slices and relative in Volume 2, Number 3, September 1997, pages 259-278. amplitude maps at the target reflection clearly delineate the

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Infracambrian Salt Basin in the North Oman Salt Flank Western Rub’ Al Khali, Saudi Arabia Diapir Exploration

Mohammad I. Faqira and Ali Y. Al-Hawuaj Tom Faulkner Saudi Aramco Petroleum Development Oman

An Infracambrian salt basin has been identified in the Salt diapir flank traps are a mature exploration target in many western Rub’ Al Khali based on 2-D seismic data and is parts of the world but are, as yet, untested in Oman. The supported by low gravity and strong structural growth over upside potential for diapir flank traps appears promising as the salt. This basin developed in a subsiding graben located considerable reserves have already been booked in the crestal along the extension of the northwest-southeast trending Najd anticlines above the diapir heads such as the Ghaba North. fault system. The Najd fault system consists of west- stepping left-lateral, strike-slip faults, with rhomb-shaped Recent activities over six key diapirs in the Ghaba Salt Basin basins developed between the faults. This basin probably has increased our understanding of the diapir flank play and developed at the same time as other salt basins in the southern its uncertainties to the point where it is now appropriate to Gulf and Oman salt basins. Salt growth is evident on the 2- drill. Numerous play opportunities are envisaged as the D seismic data, and it started during the Early Cambrian Infracambrian Ara salt (part of the Huqf Supergroup) rises and continued until the Late Cretaceous. up from as deep as 10 kilometers and locally reaches the present surface. Exploration targets include the Natih, The hydrocarbon potential of the Infracambrian salt Shu'aiba, Al-Khata, Gharif and Haima. structures is high due to (1) the potential presence of Infracambrian source rocks equivalent to those in the Huqf Tom Faulkner (see abstract "The Athel Play in Oman: Group of Oman as well as the known source rocks of the Controls on Reservoir Quality" on page 61 for biography Silurian Qusaiba shale; (2) the early growth of salt structures and photograph) that may capture any migrated hydrocarbon and preserve porosities from destruction by diagenesis; and (3) the preservation of these structural traps throughout subsequent Challenges in Carbonate Reservoir geologic history. Characterization by Integrating Mohammad I. Faqira is an Horizontal Well Data: A Case Study Explorationist with Central Area from Dukhan Arab-C Reservoir, Qatar Exploration of Saudi Aramco since 1994. Mohammad acquired a BSc Jorge S. Gomes and Ali M. Said Trabelsi from King Abdulaziz University in Qatar General Petroleum Corporation 1985 and a MSc from the Colorado School of Mines in 1991. He joined The Arab-C reservoir, which is one of the main oil reservoirs Saudi Aramco in 1987 and since then in the giant Dukhan field, consists of a stratified sequence worked for Geophysical Processing, of limestones, dolomites, and some anhydrites representing Red Sea Area Exploration and lagoonal, tidal flat, and sabkha environments. In terms of Central Area Exploration. Mohammad is currently working overall reservoir properties, and for field development in the Western Rub' Al Khali area. purposes, the reservoir is divided into two units: the Upper Arab-C Unit (UAC) is more stratified (higher cyclicity) and Ali Y. Al-Hawuaj is Chief has relatively low reservoir quality, while the Lower Arab- Explorationist for the Eastern Area C Unit (LAC) is less stratified, and exhibits much better with Saudi Aramco. He has over 18 reservoir quality. Average thickness is about 85 feet, average years of experience with Saudi porosity is 15-20%, and permeability is variable. The Aramco, mostly in exploration and reservoir performance to date is dominated by an interval exploration management. Ali holds of 10 to15 feet at the base of the LAC. The average a BSc degree in Geology from King permeability of this basal grainstone is about 250 mD Fahd University of Petroleum and compared to a reservoir average of 30 mD. Because of the Minerals and is a member of the reduced contrasting permeabilities of the UAC relative to AAPG and DGS. the LAC, the UAC is being developed with horizontal wells.

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Data derived from horizontal wells, namely cores, serve as Plate Tectonic Control of Petroleum an excellent source of information in improving the description of this reservoir, particularly with respect to Occurrences of the Arabian Peninsula lateral variations of key genetic units and their petrophysical trends. The small-scale spatial variability of reservoir Ingeborg Guba properties can be captured with horizontal variograms. Sultan Qaboos University, Oman However, the integration of vertical and horizontal well variograms provide important challenges in reservoir The geological history of the Arabian Peninsula saw a series description. By combining these variograms with ones of very fortunate geological processes, which led to an derived from vertical wells, it is possible to capture different accumulation of 645 billion barrels of crude oil, accounting scales of heterogeneity. for nearly 70% of the world's total recoverable oil reserves. The various geological conditions needed for these huge In this paper we explain how borehole images, petrographic hydrocarbon concentrations are all provided by plate analysis, and conventional electric logs along horizontal tectonics. wells are being integrated with spatial correlation models to improve the stochastic reservoir description of this This paper investigates the plate tectonic history of the heterogeneous reservoir. We also explain how to identify Arabian Plate and its relationship to the basins in which facies, record their lateral extent and orientation, their source rocks of sufficient thickness could accumulate, as respective petrophysical variabilities and locate fractures. well as to conditions of maturation and migration. In The current reservoir description models for the Dukhan particular, the development of structural traps along the Arab-C reservoir are reinforced by valuable information northeastern plate boundary parallel to the Arabian Gulf are derived from these new horizontal wells. highlighted.

Jorge S. Gomes joined Qatar The Arabian Plate is currently drifting by more than 2 General Petroleum Corporation centimeters per year to the northeast, where it crushes against (QGPC) in 1993 and is currently the the Eurasian Plate to form the Zagros-Taurus collision zone. Head of a Field Development Team. This drift of the plate means enormous horizontal stress on He has been in the industry for over the rocks, the deformational effects of which can be recorded 17 years in a variety of assignments throughout the Arabian Peninsula. with British Petroleum, EDMA, PECTEN and PARTEX. He holds BSc The constellation of stresses caused by the plate tectonical and MSc degrees in Geology from movements enables the petroleum geologist to predict the Oporto University (Portugal) and a location and extension of unexplored sedimentary basins, MEng in Petroleum Engineering from Herriot-Watt the geometry of yet unknown structural traps, and the University, UK. His professional interests are Middle East presence, attitude, and density of fractures in new oil fields. Mesozoic carbonates, deterministic and stochastic modelling of carbonate properties, and the application of Ingeborg Guba earned a PhD degree 3-D geologic models in reservoir simulation and field in Geology from Technical University development. Clausthal in Germany. She has worked as Geologist for uranium Ali M. Said Trabelsi is a Reservoir mines in Germany and as Consultant Geologist/Sedimentologist with for iron mines in Brazil. Ingeborg Qatar General Petroleum has taught at Yarmouk University in Corporation (QGPC). Before joining Jordan, and teaches at present at the QGPC, he was Vice-President of Department of Petroleum & Mining Petro-Reservoir Characterization, Engineering, College of Engineering Inc. in Houston. He also worked for at Sultan Qaboos University in Oman. David K. Davies and Associates in Houston, 3-D Exploration Inc. and Exxon. Ali has consulted for many GEO’98: Field Trip oil companies in Houston including Exxon, Enron, Mitchell Holocene Carbonates and Evaporites of Abu Dhabi Energy, Seagull Energy, United Energy Partners and 23-25 April, 1998 Ecopetrol in Colombia. Ali received his MSc and PhD For more information please contact: degrees from Texas Tech University. A.S. Alsharhan, P.O.Box 17325, Al Ain, UAE Fax: (971 3) 611-601 e-mail: [email protected]

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Petrophysical Characteristics and Nuclear Magnetic Resonance Logging Hydrocarbon Trapping in the in Petroleum Development Oman, Triassic Reservoirs of the Experience to Date Oued Mya Basin, Algeria Asbjorn Gyllensten Nacer E. Guellati Abu Dhabi Company for Onshore Oil Operations Sonatrach Exploration (previously Petroleum Development Oman)

The Oued Mya basin is located on the north part of the The perceived value of recent developments in Nuclear Saharan platform. The area lies between the giant Hassi Magnetic Resonance (NMR) logging technology lies mainly R'Mel gas field and the Hassi Messaoud oil field. Since the in its potential to reduce well testing by providing log- discovery of the giant Hassi R'Mel gas field in 1956 in the derived producibility data and permeability input to reservoir Triassic reservoirs, many accumulations of oil have been models, with the ultimate aim to locate the remaining oil in found in these reservoirs, such as Haoud Berkaoui, Benkahla, mature fields. Oued Noumer, Djorf, Guellala, Oulouga and Boukhzana. The lower part of the Triassic is formed by clastic sediments, The first NMR-trials in clastic environments in South Oman sometimes with intercalations of volcanic rocks in the lowest in 1993 confirmed the limitations of “traditional” NMR member, while the upper part is essentially composed of log-interpretation in heavy, viscous crude, where the tool thick and widespread evaporites, mainly salts that constitute can no longer differentiate between clay-bound water and a seal for the Triassic reservoirs. The Triassic clastic movable oil. Careful analysis of the data led, however, to a formation is divided into four main lithologic members new method to determine oil saturation using diffusion which are called from base to top: Série inférieure, T1, T2, information. Subsequent improvements in NMR-logging and Argileux inférieur. tools and interpretation techniques, together with a series of core analyses and feasibility studies, provided The 'Série inférieure' and 'T1' members are the best reservoirs encouragement to embark on a second round of trials in as they correspond to fluvial deposits. The 'T2' Member 1995/96. These new studies focused on light oil applications. has usually fair to poor reservoir characteristics because the Residual Oil Saturation (ROS) determination in clastic sandstones become more shale- and salt-cemented. The reservoirs was successful and NMR-logging was extended 'Argileux' Member is mainly composed of shales. to carbonate formations in North Oman.

The petrophysical characteristics of the reservoirs are In order to reduce operating costs it is important to maximize controled by the depositional environment, sandstone the value of our data-acquisition strategies. Establishing a sources, the petrographic composition, burial and diagenetic reasonable expectation of technical success up front Ð before phenomena. The porosity decreases with depth because of committing to mobilization of expensive new sensors Ð compaction with burial and also by cementation. Besides facilitated the introduction of this new technology in our quartz overgrowth cement, illite, anhydrite, dolomite and operations. On the basis of the results of these trials we can salt cement are present in significant rates to reduce or now map out areas where NMR-logs can complement obstruct the pore spaces. Porosity gain occurs by dissolution conventional logging tools and where we need to focus on phenomena. further research and development.

Many observations confirm that hydrocarbon trapping Asbjorn Gyllensten graduated from prevented further quartz cementation. Hydrocarbon traps Norway’s Technical University in are structural, stratigraphic and mixed type in relation with Trondheim with a MSc in Electrical the geometry of the sand bodies. The source rock is the Engineering and worked for Silurian-rich organic "hot shales". The expulsion and Schlumberger in the Far East and migration started since the Cretaceous. Africa as a Logging Engineer. In 1978, Asbjorn joined Shell after Nacer E. Guellati graduated as completing an MBA at INSEAD in Geologist Engineer from the Algerian Fontainebleau, France. In the Hague Petroleum Institute in 1982. He he provided petrophysical support for joined Sonatrach in the same year the Shell Group Operating Companies and Single String and is currently Chief Geologist of Ventures before he transferred to Petroleum Development the Exploration Division. Oman (PDO) as a Petrophysicist. From 1983 to 1987 he worked in London for Shell EXPRO UK as a Senior Petrophysicist responsible for Southern North Sea gas fields, exploration support and special core analysis. He then

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moved to Shell Nigeria as Head of Petrophysics and emplacement within Central Saudi Arabia. Further, the Petroleum Engineering Area Team Leader in Warri, Khuff reservoir at two Nuayyim wells cannot be in spearheading the South Forcados Area Development. In communication with the underlying Unayzah. The gas 1993 Asbjorn returned to PDO as Team Leader Exploration chromatographic fingerprints of the Unayzah-B oils form a Petrophysics, responsible for evaluation, completion and tight grouping suggesting a high degree of reservoir testing 35-40 wells/year. He recently transferred to Abu connectivity. Fingerprints of Unayzah-A oils are variable, Dhabi Company for Onshore Oil Operations in Abu Dhabi, strongly implying that the reservoir is compartmentalized. United Arab Emirates as Petrophysical Coordinator, Compartmentalization is expected, given the presence of at Petroleum Development Division. Asbjorn is a member of least some low permeability units within the Unayzah-A the SPWLA and SPE and serves on the 1998 SPE Well reservoir, and some extensive non-reservoir facies in the Logging Technical Committee. Basal Khuff Clastics reservoir. These expectations are confirmed by differences in oil composition.

Geochemical Evidence for Reservoir Henry I. Halpern and Mark H. Tobey (see abstract "Geochemistry of Eastern Saudi Arabian Paleozoic Gas/ Compartmentalization in Central Arabian Condensates" on page 80 for biography and photograph) Paleozoic Reservoirs William (Bill) M. Petersen is a Henry I. Halpern, Mark H. Tobey, Geophysicist with the Area William M. Petersen, William J. Carrigan, Exploration Department of Saudi Peter J. Jones, Mohammad R. Al-Khadhrawi, Aramco. Prior to joining Saudi Mohammad A. Al-Amoudi and Hani O. Al-Ohaily Aramco in 1991, Bill worked with Saudi Aramco Seismograph Service Corp. (1967- 1976); American Independent Oil Geochemical and geological interpretations are integrated Company (1976-1979); Amoco (1979- to understand intra-reservoir fluid communication at five 1986); and Geo-Services fields in Central Saudi Arabia. Well control at four of these International (1986-1991). He fields Dilam, Raghib, Abu Rakiz, and Abu Markhah is received a BSc degree (1964) in Earth Sciences from the limited. Therefore, the additional insights gleaned from the Massachusetts Institute of Technology and a MSc degree in geochemistry of the hydrocarbon fluids recovered are Geophysics from the University of Houston in 1991. particularly important for future delineation drilling decisions at these fields. The application of stable isotope William J. Carrigan and Peter J. Jones (see abstract geochemistry, rock pyrolysis and well-log interpretations, "Geochemistry of Eastern Saudi Arabian Paleozoic Gas/ and hydrocarbon chromatographic signature techniques have Condensates" on page 79 for biographies and photographs) shown that the oils at two Dilam wells may be in fluid communication (although they are interpreted to be Mohammad R. Al-Khadhrawi has reservoired in different formations), but the gas/condensates been a Research Scientist with the at the two wells are not in communication. Additionally, Geochemistry Unit of the Lab R&D the oil and gas at one of the Dilam wells do not appear to be Center in Saudi Aramco since in fluid communication, and the gas reservoirs at Raghib November 1991. He received a BSc and Dilam are not in communication. A reservoir degree in Industrial Chemistry in discontinuity exists within the Unayzah at Abu Markhah, 1991 and a MSc degree in Chemistry which precludes fluid communication between the two Abu in 1996. Mohammad has been Markhah wells. Isotopic differences exist between the Abu working on various research projects Markhah and Abu Rakiz fluids, as well. in reservoir geochemistry (continuity and fluid contacts studies) as well as At Nuayyim field, oils from the three reservoirs, Basal Khuff exploration geochemistry in Central and Eastern Saudi Clastics, Unayzah-A and Unayzah-B exhibit highly variable Arabia. gas chromatographic fingerprinting signatures. In addition, several of the Basal Khuff Clastics crudes have extremely Mohammad A. Al-Amoudi has been light carbon isotopic signatures and distinctly different with Saudi Aramco since 1988. He fingerprints than any of the Unayzah oils. These differences is a Laboratory Technician with the can be related both to in-reservoir alteration, as well as to Lab R&D Center of Saudi Aramco. the timing and mechanism of emplacement of the oils. The unusual oils found in several of the Khuff Clastics tests are likely due to different stages and/or different source areas (kitchens) of hydrocarbon generation, migration, and

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Hani O. Al-Ohaily is a Laboratory sands, fining-up into floodplain fines to playa lake shales, Scientist with the Lab R&D Center acts as seal. The uppermost Runib Member consists of sheet/ of Saudi Aramco. He received a BSc channel sandstones alternating with playa deposits and degree in Chemistry from King Saud represents a waste zone. University in 1984. His research interests include reservoir fluid Traps, presently draping the pre-salt topography, were properties (similarities and generated and charged following multiple phases of salt variations). withdrawal and dissolution. Production data indicate that structures are compartmentalized by faults, clearly expressed both on seismic and FMI data.

The Karim play has three critical success factors: (1) The Karim Oilplay: Cambrian reservoir-seal development: the presence of reservoir sands Alluvial-Lacustrine Deposits overlain by a well-developed seal is limited to the southwest part of the Karim basin; (2) oil quality: there is a clear API- in South-Central Oman depth trend and oil becomes more viscous towards the east flank; and (3) reservoir quality: reservoirs become tighter Christel Hartkamp-Bakker with depth towards the basin. Petroleum Development Oman Luppo Kuilman These critical success factors are being used to rank 20 Saga Petroleum (previously Shell International) prospects and leads remaining and guide the exploration and Heiko W. Oterdoom strategy for the play. Petroleum Development Oman Christel Hartkamp-Bakker is an Along the eastern flank of South Oman, in a mature Operational Sedimentologist at exploration area, drilling recently demonstrated a new Petroleum Development Oman successful play in the alluvial-fluvial sediments near the (PDO). After joining PDO, she top of the Huqf Supergroup. These sediments belong to the worked on basin studies and Lower Cambrian Karim Formation, a unit long known for Formation Micro Indicator analysis. its oil shows but considered a waste zone. The first Christel obtained a MSc in Geology 3 ° commercial discovery, Khaleel-1, tested 500 m 30 API from the University of Utrecht in 1987 oil/day in the Karim fairway from fluvial reservoirs. At and a PhD in Petroleum Geology present the Karim Formation cannot be resolved on seismic from the University of Technology in data, and structure maps of the Huqf-Karim interface, the Delft in 1993. base reservoir, are used for prospect mapping. A regional stratigraphic-sedimentological study led to the present Luppo Kuilman has recently been assigned to Saga success. Petroleum, Norway. He worked with Shell International for 12 years in various geological environments as Seismic The Karim Formation records deposition during a late syn- Interpreter. He received a MSc degree in Geology from the rift transpressional event in the Early Cambrian (Nadi strike- Free University in Amsterdam in 1985. slip related) before the onset of a thermal sag. The study revealed three major alluvial fans shedding from the Heiko W. Oterdoom is Head of southwest to northeast, onlapping onto the South Oman Salt Operations in Petroleum Development Basin. Formation Micro Indicator (FMI) paleo-current data Oman’s Exploration Lab. After indicate a northeastern-directed drainage pattern. This is joining Shell, he worked on source confirmed by the overall Net/Gross trend, which decreases rock characterization in KSEPL and in accordance with the drainage patterns. The two northern with oil shales in SIPM. Heiko has fans inter-finger with heterolithic lacustrine shales, and, worked as a Team Geologist in here, the Karim is composed of regionally correlatable Norway, Thailand and The retrogradational and progradational cycles of alluvial fan Netherlands, in NAM also as a channel complexes. In these fans the Karim is subdivided WSPE. He obtained a PhD in into three members, of which the basal Khaleel Member Petrography from the Federal Institute of Technology, Zurich consists of fluvial sheet sandstones and forms the reservoir. in 1981. The overlying Irad Member consists of fluvial channel

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A Review of NMR-Derived Permeability Hilal Al-Waheed graduated from the University of Tulsa with a BSc in in Saudi Arabia Carbonates Petroleum Engineering in 1984. He has worked in production and drilling Talal H. Hassoun, Robert Ballay, Hilal Al-Waheed engineering. Hilal joined the Saudi Aramco Reservoir Description Division of and Laurent Moinard Saudi Aramco in 1987. Schlumberger Middle East

Conventional well logs measure parameters related to static rock properties, such as porosity and lithology. Permeability, being a dynamic phenomenon, is difficult to estimate from Laurent Moinard is a Petrophysicist these parameters. Empirical transforms have been with Schlumberger, based in Al- established, which relate permeability to porosity and other Khobar, Saudi Arabia. After four static properties. These transforms provide satisfactory years as a Field Engineer in the results in clastics, but often fail in carbonates where rock Middle East, he has been working on texture in combination with porosity is more significant than log evaluation for the last twenty porosity alone. The Nuclear Magnetic Resonance (NMR) years in Europe, North America, log, which measures the distribution of pore sizes in the India and the Middle East. rock, and gives an indication of texture and facies type, allows a more accurate estimation of permeability.

Over the years, Saudi Aramco has recorded NMR logs in some of the most prolific carbonate producers in Saudi Arabia. In this paper, we present the results to-date of the Advances in Seismic Acquisition effort to derive permeability from well logs. Five different in Saudi Arabia carbonates formations from wells in three different fields are considered. NMR-derived permeability is compared to Richard Hastings-James core data and a traditional, historically-calibrated, and Abdulmohsin Y. Al-Dulaijan permeability-porosity transform. Although the core/NMR Saudi Aramco database is, at present, not large enough to permit definitive conclusions, we observe an improvement in using the pore During 1997 Saudi Aramco reached its highest level ever size indication from NMR in the estimation of permeability. of seismic crew activity, with eight 2-D seismic crews and two 3-D seismic crews deployed in the field. This has resulted Talal H. Hassoun holds MSc degrees in the acquisition of about 24,000 kilometers of 2-D and in Petroleum Engineering and in about 2,500 square kilometers of 3-D seismic data. System Engineering. He has worked in reservoir engineering in Libya and This paper describes several acquisition techniques that have Houston (Gulf Oil Corporation). been developed and implemented by Saudi Aramco over Talal joined Saudi Aramco in 1979 the past year in support of exploration and reservoir and held assignments in reservoir development activities. They include 2-D swath acquisition management for twelve years, primarily for use in areas with imaging problems, 2-D off- production engineering for one year, end acquisition using small group intervals for improved and is presently in reservoir stratigraphic resolution, and 3-D split double zig-zag swath description. acquisition that results in excellent source-to-receiver offset and azimuthal distributions. Robert Ballay holds a PhD in Theoretical Physics. He has taught The 2-D techniques presented assume the availability of 480 physics in two universities and held recording channels, which is now the Saudi Aramco standard petrophysical engineering 2-D crew configuration. The new 3-D split double zig-zag assignments in Texas, Alaska, technique will work with any 3-D crew. Indonesia, California and Saudi Arabia. Data examples will be used to show that, if used appropriately, these various techniques have the potential to enhance data quality at a modest increase in cost.

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Richard Hastings-James is currently would make the Unayzah Formation a southern hemisphere Geophysical Consultant with Saudi cold-climate desert (“present is key to the past”). This Aramco. He has 17 years of observation is consistent with the documented (Permo- exploration industry experience, 12 Carboniferous) glaciogenic sequences of the Al-Khlata of which were with Amoco Formation of southeast Oman, and is roughly coeval with Production Company in Canada, the Permian (Rotliegend) tropical desert conditions over Houston and various locations northwest Europe. An eolian peri-glacial depositional model throughout Africa and the Middle links the Unayzah Formation of the Saudi Arabia to the East. Prior to that, Richard was an Permian glaciogenic Al-Khlata Formation of Oman in time. Associate Professor at the Technical University of Nova Scotia, Canada and a Research Fellow Christian J. Heine (see abstract "3-D Seismic Coherency at Pembroke College, Oxford. He has been with the Attributes for Improved Imaging of Subtle Faults and Geophysical Data Acquisition Division of Saudi Aramco Stratigraphic Features" on page 85 for biography and since 1992. Richard has a BEng degree in Electrical photograph) Engineering from the Technical University of Nova Scotia and a PhD from Trinity College, Cambridge. He is a member Kenneth W. Glennie received his of the SEG and Dhahran Geological Society. BSc and MSc degrees from Edinburgh University. He then spent Abdulmohsin Y. Al-Dulaijan has the next 32 years as an Exploration been with Saudi Aramco for 16 years Geologist with Shell, working in New and is currently the Chief Zealand, Canada, Nepal, Oman, Geophysicist of the Geophysical Data Iran and Turkey before spending 15 Acquisition Division. He has BSc and years on the North Sea geology MSc degrees in Physics from based in London. He retired from Baghdad University. Abdulmohsin Shell in 1987, and he is an Honorary also holds an MSc in Engineering Lecturer at Aberdeen University, spending part of each year Geosciences (1985) from the since 1990 working on the desert of southeastern Arabia University of California, Berkeley, and maintaining his interest in the Oman Mountains. He and a PhD in Geophysical Engineering (1991) from is a member of the AAPG and Geological Society of London, Colorado School of Mines. Edinburgh, Aberdeen and The Netherlands.

Brian P.J. Williams obtained a BSc Peri-Glacial Dune Sand Reservoirs of the (Honors) in Geology and a PhD in Permian Unayzah Formation, Sedimentology from the University of Wales. From 1964 to 1970 he Central Saudi Arabia worked as a Post-doctoral Research Fellow at the University of Ottawa, Christian J. Heine, Saudi Aramco Research Fellow at the University of Kenneth W. Glennie and Brian P.J. Williams Wales, and a Senior Hydrogeologist University of Aberdeen for the Water Resources Board in Reading. From 1970 onwards Brian The recognition of Permian-age eolian sandstone was an was a Lecturer, Senior Lecturer and Reader in important milestone in the evaluation of the Unayzah Sedimentology in the Department of Geology, University reservoirs in Central Saudi Arabia. To date, 15 fields have of Bristol. In 1988, Brian became Professor in Petroleum been discovered along the trend where the primary producing Geology at the University of Aberdeen where he is the horizon is the Unayzah Formation. Borehole image data Director of the MSc course in Petroleum Geology. His from the distinctly eolian reservoirs indicate a dominant wind current research interests include hydrocarbon reservoirs direction from west to east, which holds true for all the in Australia, Canada, Texas and the North Sea; non-marine sandstone recognized as eolian. A reconstruction of the clastic sedimentology and basin analysis. Brian is a Arabian Plate during the Permian suggests the eolian member of the Institute of Petroleum, SPE, PESGB, AAPG, transport direction would fit with the present location of the Society for Sedimentary Geology, International Association “roaring Forties”, a dominant southeast wind direction in of Sedimentologists and the Geological Society of London. the southern hemisphere south of the 30th parallel, which

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Gondwana and the creation of the northeastern and Distribution and Formation of southeastern passive margins of the Arabian Plate. In this Pyrobitumen in Haima Reservoirs tectonic framework a reservoired charge of oil which has in North Oman been emplaced during the first burial event and which has been uplifted to a sufficiently shallow depth corresponds to Alain-Yves Huc, Institut Français du Pétrole a favorable situation for biodegradation to take place. In and Peter J.R. Nederlof this situation formation of high gravity oil accumulation (and Petroleum Development of Oman possibly tar sand) can be expected. Upon the subsequent phase of burial this heavy oil eventually will undergo thermal Occurrences of bitumen affecting the porosity has been cracking and be transformed into a pyrobitumen-rich reported in the Cambro-Ordovician reservoirs of the Haima reservoir. This scenario which is proposed to account for supergroup of North Oman. The considered geographical the high pyrobitumen content of Jaleel and Al Bashair wells area encompasses the Fahud Salt Basin, the Makarem- has been simulated by numerical modeling. Mabrouk High and the Ghaba Salt Basin. The regional implication is that the pyrobitumen occurrence According to their geochemical properties, including and importance can be tentatively predicted by identifying insolubility in organic solvents, elemental analysis, the age of the first reservoir charging and by assessing the spectroscopy, reflectivity, these bitumens can be recognized depth reached by the reservoir during uplifting. Reservoirs as pyrobitumen which derive from the thermal cracking of which have been charged before the uplifting and which a previous charge of oil. Besides pyrobitumen the studied have been brought to shallow depth before Mesozoic- reservoir rocks contain variable amount of extractable Cenozoic burial are likely to exhibit porosity plugged by organic material. Isotopic signatures show that (1) regionally substantial amount of pyrobitumen. Reservoirs initially the pyrobitumens have different genetic origins, that is,oil charged after the uplifting phase, or which have never is sourced by the Huqf Formation in Jaleel and Al Bashair reached shallow depth during uplifting, will exhibit only wells and oil derived is from the so-called Q and B source subordinate amount of pyrobitumen owing a sufficient rocks in Saih Rawl and Farha wells; and (2) in the studied thermal history. Consequently usual basin modeling, reservoirs the associated extractable organic matter is including mapping of regional backstriping and hydrocarbon genetically not related to the pyrobitumen and derive from generation timing, is a potential predictive tool for different source rocks. This observation implies a complex pyrobitumen occurrence in north Oman. infilling history of the considered reservoirs with several hydrocarbon charges involved in the process. Alain-Yves Huc joined Institut Français du Pétrole in 1981 and is As far as their microscopic distribution is concerned the currently Head of Organic pyrobitumen occurs as pore filling particles or as pore lining Geochemistry. Alain was educated films. The impact on the porosity alteration is highly variable at the University of Nancy, France, and the volumetric amount of pyrobitumen ranges from less and received his PhD in Organic than 1% up to 40% (in the Jaleel well) of the pore volume. Geochemistry from the University of Strasbourg, France, in 1978. He Based on numerical modeling of oil cracking the onset of spent a year and a half as a pyrobitumen generation in the studied wells is postulated to postdoctoral fellow at Woods Hole be a recent event in the basin history (less than 50 million Oceanographic Institution, USA, and two years as a CNRS years). According to pyrolysis experiments performed on researcher at the Applied Geology Department of the several types of oils, regarded as possible precursors for the University of Orléans, France. He is a member of the AAPG, pyrobitumen, we infer that the amount of formed EAOG, EAPG and ALAGO and has published more than pyrobitumen is directly related to the quantity of NSO 80 papers on geological and geochemical subjects. compounds present in the precursor oil. In this respect fields which exhibit unusual quantity of pyrobitumen are assumed Peter J.R. Nederlof is a Geochemical to have hosted oil with a very high gravity. Such a situation Consultant with Shell with 18 years can be the result of the biodegradation of an initially of oil industry experience in Europe, conventional oil. North America and the Middle East. Peter was previously Team Leader of Schematically the regional tectonic history includes a first Regional Studies in Petroleum burial phase related to Infracambrian to Ordovician periods Development Oman. Before joining of rifting followed by an important phase of erosion, caused PDO in 1992, he was employed by by a very broad uplift of eastern Oman during Late Shell Canada and Shell Research in Paleozoic. The subsequent phase of burial leading to the The Netherlands. Peter's main present day depth has been initiated by the break-up of the

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interests lie in the field of reservoir geochemistry and Joerg E. Mattner (see abstract "Integrating Fluid Flow and hydrocarbon habitat studies. He obtained a PhD in Borehole Imaging Data in Fracture Characterization, Chemistry from the University of Amsterdam and did a Post Hanifa Reservoir, Abqaiq Field, Saudi Arabia" on page 44 Doctorate at Stanford University. Peter is a member of the for biography and photograph) Board of the European Association of Organic Geochemists and an active member of the AAPG and the American Yayha M. Al-Ansari received his BSc Chemical Society. Peter has been a member of the Editorial in Geology from Qatar University in Advisory Board of GeoArabia since its launch in 1996. 1993. He joined the Bahrain National Oil Company as a Trainee Geologist in September, 1993. Later he worked as Development Geologist Correlation Between Geomorphological for three years and was involved in Lineaments and Fractures Observed in reservoir characterization and Outcrop with Subsurface Faults in the formation evaluation research. He Mauddud Formation, Awali Anticline, is currently working as Exploration Bahrain Geologist in onshore and offshore areas.

Inga Hustedt, Joerg E. Mattner Western Atlas International Cycles of Generation, Migration, and Yayha M. Al-Ansari Accumulation and Destruction Bahrain National Oil Company of Hydrocarbons in Iraq Fractures and small-scale faults commonly cause production Muhammad W. Ibrahim problems during advanced depletion stages of hydrocarbon Target Exploration Consultants reservoirs. Detailed knowledge of fractures and faults prior to the occurrence of early water/gas ‘breakthrough’ (or Syndepositional bitumen pebbles in some Cretaceous rocks bypassed oil) allows for optimization of reservoir of Iraq indicates generation, migration, accumulation, management. The Awali Anticline has excellent large-scale seepage, and destruction of some paleo-oil traps before and surface/bedrock exposures. In addition the long production during the Cretaceous. history and drilling activity has resulted in detailed subsurface fault maps of shallow reservoirs. This study In view of surface and subsurface rock evidence, there compares and correlates the subsurface faults with structural should have been significant source rocks, older than the features of various scales from strata exposed in the Awali acclaimed Balambo Formation responsible for generating Anticline. The comparison incorporates trend statistics, hydrocarbons before the Cretaceous. fractal dimensions, length distribution, parent-daughter relationships and aerial density of structural features. This However, published geochemical source rock analyses not is a unique possibility to evaluate the extent to which only estimate a Miocene-Eocene times for the onset of oil structural outcrop/surface data can aid in the prediction of generation, but also predict a total volume of generated fractures and faults in the subsurface of the Arabian Gulf hydrocarbons that is less than the proven in-place region. hydrocarbon reserves in Iraq. Inga Hustedt graduated in 1996 from Cycles of hydrocarbon generation, migration, accumulation the Technical University of Clausthal and destruction were modeled to account for the presently (Germany) in Geology. During her entrapped hydrocarbons and the predecessors of the studies she worked on assignments in Cretaceous syndepositional bitumen pebbles in Iraq. the department of Petroleum Geology. Her thesis was an industry Muhammad W. Ibrahim holds a BSc project examining the occurrence of degree in Geology and MSc and PhD tectonic elements and their degrees in Petroleum Geology. He connection to hazardous surface gas has more than fifteen years flows in the coal mining district of experience in exploration and Ruhrgebiet, Germany. Prior to moving to Bahrain as an development geology. Muhammad is independent geologist in 1997, she worked as a consultant currently Regional and Development in environmental engineering. Geologist with Target Exploration Consultants, UK. He has also worked as Geologist with Lasmo

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Grand Maghreb and Lasmo International, London, in 1991, The objective of the study was to assess the further and with Mobil Oil Libya/Veba Oil Operations in Tripoli, hydrocarbon potential of the area by determining the Libya. Muhammad was Assistant Professor and Head of geological evolution of the block in relation to where and Department of Petroleum Geology at King Abdul Aziz when hydrocarbons generated, and how they migrated into University, Jeddah between 1978 and 1980. Muhammad is the Bishri Block. a member of the Iraqi Geological Society, AAPG, PESGB and COGS. The timing of the various fault directions and movements were ascertained from detailed interpretation of high quality 3-D seismic over the block. The movements on the Bishri Paleozoic Hydrocarbon Potential Block were placed into their regional geological and structural setting using regional 2-D seismic data and well of Western Iraq interpretations which was also included in the basin modelling analysis using the PGS HEDERA basin modeling Muhammad W. Ibrahim system. Target Exploration Consultants A local hydrocarbon charge hypothesis was precluded since; Regional stratigraphy, tectonics, source, reservoir and cap reservoir rocks in Bishri are stratigraphically below the rocks of northern Arabia were integrated to assess expected, highly oil prone, Upper Cretaceous source rocks; hydrocarbon potential of the inverted Paleozoic intracratonic fault throws are generally minor, with significant strike-slip basins of western Iraq (area south of latitude 35N and west elements not favoring downward migration; and that of longitude 43E). Oil discoveries in western Iraq were modeling predicts source rock to be immature within the made by MPC before 1960 in the vicinity of a large oil block. However, simulation of the regional cross-sections seepage at Hit (Heet) in the east-northeastern part of the indicates that the adjacent Euphrates Graben containing a study area. A giant Paleozoic gas-condensate field was thick and stratigraphically broad source rock section, discovered by Iraq’s Oil Exploration Co. in 1993 at well produces hydrocarbons into the Upper Cretaceous carrier Akkas-1. Exploration success has been exceptionally high system, which then steps down into the Lower Cretaceous in western Iraq with excellent discovery/dry hole ratio of 5/ reservoirs and carrier systems at the locations of major rift 3 to 7/1 (commercial discovery/dry hole ratio to producible margin normal faults. discovery/ dry hole ratio). Within the study area 13 proven immature to frontier plays in Paleozoic, Mesozoic and The Bishri Block formed as a large fold in Early Eocene Cenozoic rocks have been recognized, and there are over times, and modeling indicates hydrocarbon charge from the 68 areas of interest containing more than 70 undrilled surface east and northeast occurred from the Eocene through to and subsurface structures. Total ultimately proven Miocene times. Late Pliocene movements not only switched recoverable reserves in the studied area in western Iraq are off the charge, but also likely breached seals and redistributed estimated to be more than 1.2 billion barrels of heavy oil to the hydrocarbons into their present accumulations, which condensates. This estimate does not include large asphalt is further modified by significant hydrodynamic deposits at Hit and natural gas reserves at Akkas-1. groundwater flow. The provenance of the oils suggests a westwards filling and spilling history, with further Muhammad W. Ibrahim (see abstract "Cycles of exploration implications. Generation, Migration, Accumulation and Destruction of Hydrocarbons in Iraq" on page 102 for biography and James Illiffe received his BSc degree (Honors) in Geology photograph) from Swansea College, University of Wales in 1982, his MSc and PhD in Geology from the University of South Carolina in 1985 and 1991 respectively. For the past six years as The Hydrocarbon Charge to the Manager of Basin Modeling for PGS Tigress, he has been Bishri Block, Palmyrides, Syria: the technical expert developing HEDERA, a commercial basin modeling software system. He has worked on many An Integrated Multi-disciplinary Study integrated exploration studies, including the Atlantic Margin from Ireland to Norway, Mozambique, Sudan, Gulf Coast James Illiffe, PGS Tigress (UK) Ltd. USA, Egypt and Syria. James is presently working as Carl Blackstock and Ian Bulley Geological Advisor in the Integrated Service Group of PGS Reservoir (UK) Ltd. Conoco Inc., in Houston, Texas, USA. The Bishri Block is a prominent topographic high located on the eastern end of the Palmyrides fold belt in Syria. Bishri has proven hydrocarbons in the Lower Cretaceous Rutba and Hayan Formations, and an asphalt mine at the surface.

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Carl Blackstock graduated with a thick fluvial sandstone sequence (Quweira Formation and Geology degree from Exeter Saq Sandstone) that corresponds to a vertical aggradation University in 1980. He joined British of braided alluvial systems showing tidal influences at the Petroleum as an Interpretation top. This unit is abruptly overlain by transgressive wave- Geophysicist and worked in the UK, to tide-dominated deposits of the lower Qasim Formation Ireland and China, principally on (Hanadir and Kahfah members), followed by offshore facies exploration acreage. In 1991 Carl at the base of the Ra’an member that reflect the maximum joined a UK Consultancy (now part flooding of this cycle. The seaward-stepping offshore to of PGS Reservoir) and has worked shoreface/foreshore sequences of the Ra’an to Quwarah extensively on exploration and Members represent the regressive part of the cycle, the upper development projects worldwide. He is currently Manager boundary of which is marked by a major erosional surface of Geophysics at PGS Reservoir, UK. related to Late Ordovician glacial processes. (3) The Late Ordovician-Silurian cycle begins with unconformable Ian Bulley graduated from Reading glacial deposits of the Sarah Formation preserved in several University in 1983 and worked in the paleochannels incised into the Qasim Formation and Saq UK and Libya before gaining an MSc Sandstone. This glacial complex is bounded at the top by a in Petroleum Geology in 1988. He discontinuity (onlap surface) that marks the major rise of has since worked at Amoco, Hunt Oil sea level and correlative major flooding related to and PGS reservoir Ltd. After an deglaciation during the Early Silurian. A thick aggrading initial period working on the North then prograding unit of storm- to wave-dominated shelf Sea, he has spent the last 3 years in deposits accumulated until the end of the Silurian (Qalibah the Middle East specializing in Group). A major erosional surface bounds this third cycle. reservoir and development geology. (4) The Devonian cycle begins with the fluviatile sandstone Ian is currently in western Australia working on the sequences of the Tawil Formation (Lochkovian?); first exploration potential of the Carnarvon Basin. aggrading then backstepping, these sequences record a relative rise of base level. The continuation of this process led to the development of a mixed lagoonal environment The Paleozoic Succession of the Tabuk Basin with deposition of the Jauf Formation (Lower Devonian), the transgressive peak being marked by the Hammamiyat in Saudi Arabia: Lithostratigraphy, Limestone Member. The overlying siliciclastic bay to Sedimentology and Sequence Stratigraphy estuarine deposits mark the beginning of the regressive trend that resulted in the accumulation of fluviatile sequences of Dominique Janjou, Philippe Razin the Al Jubah Formation (Middle Devonian). The top of this Bureau de Recherches Géologiques et Minières cycle cannot be characterized because of the lack of younger Mohammed A. Halawani formations exposed in the Tabuk area. The detailed sequence Deputy Ministry for Mineral Resources, Jeddah stratigraphy of each of these transgressive-regressive cycles, Robert Wyns based on precise sedimentologic studies, could provide a Bureau de Recherches Géologiques et Minières reliable basis for subsurface correlations. and Abdallah M.S. Memesh Deputy Ministry for Mineral Resources, Jeddah Dominique Janjou received his PhD degree in Geodynamics and Outcrop studies during geological mapping in the Tabuk Structural Geology from the Basin have led to a lithostratigraphic and sedimentologic University of Paris in 1981. He joined revision of the Cambrian to Middle Devonian succession. the Bureau de Recherches The vertical facies succession makes it possible to define Géologiques et Minières (BRGM) in depositional sequences of different frequencies and a revised 1982. He was involved in mapping hierarchy of the groups, formations and members, and of programs in France (Brittany), Saudi their associated disconformities and unconformities is Arabia (Wajid Sandstone), Haiti proposed. The stacking pattern describes the four major (West Indies), Oman (Hawasina transgressive-regressive cycles that characterize this nappes), and mapping of the Paleozoic rocks of Tabuk Basin northern margin of Gondwana. (1) The Cambrian cycle, from 1990 to 1996. Dominique is currently working on GIS which unconformably overlies the irregular surface of the and digital maps. Arabian Shield, comprises a basal alluvial conglomeratic sandstone unit overlain by a mixed sand-flat - eolian Philippe Razin (see abstract "Sedimentology and Reservoir sandstone complex (Siq Formation). (2) The lower boundary Geometry of the Late Permian Upper Gharif and Lower of the Upper Cambrian-Upper Ordovician cycle corresponds Khuff Formations in Interior Oman: Outcrop Study in the to an angular unconformity. This cycle begins with a very Haushi Area" on page 82 for biography and photograph)

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Mohammed A. Halawani currently between Tabuk and Bayda Nathil, over a distance of 500 works as a Geologist in the Deputy kilometers (km) from east to west. Rapid and frequent lateral Ministry for Mineral Resources changes in facies are recorded within the glacial-related Mapping Department. He received deposits, as well as vertical repetition of facies in several his BSc degree from the Faculty of sections, this spatial organization impedes the use of Earth Sciences at King Abdul Aziz lithofacies for identifying distinctive different formations University, in 1981, after which he in the area. worked on different projects in the Arabian Shield. Since 1990, he has In the eastern part of the Tabuk Basin (Bayda Nathil - Jabal been involved in several mapping Misma area), the Sarah Formation consists of four successive projects of Phanerozoic rocks, especially in the Paleozoic lithologic units bounded by major glacial surfaces, and lies of north and northwest Saudi Arabia. unconformably over the Qasim and Saq formations. The first unit of the Sarah Formation that fills the incised Robert Wyns received his PhD paleovalleys consists of channelized fluviatile sandstone that degree in Tectonics from the locally mimics the Saq Formation and shows traction University of Paris in 1980. He structures such as trough cross-bedding. This first sandy joined the Bureau de Recherches unit is bounded by a glaciated upper surface showing a Gèologiques et Minières (BRGM) in typical "roches moutonnées" structures. Above this surface, 1981. He worked mainly on the the second unit consists of green siltstone, channelized Hercynian Belt in western France sandstone, and "exotic" blocks of igneous rocks. It is eroded during the 1980s. He was involved at the top by a second extended glacial surface. The third in the geologic mapping program of unit is represented by a massive unit of sandstone with huge the Sultanate of Oman between 1989 water-escape structures, capped by a third discontinuous and 1992, and in geologic mapping in Saudi Arabia between glacial surface. The fourth unit consists of fine-grained pink 1992 and 1994. Robert has been in charge of research and homogeneous sandstone-bearing few like-tigillites burrows. development projects on surficial deposits characterization In that area, the topmost beds of the formation are probably and mapping in France since 1995. He is a member of the cut by a Mesozoic erosional surface. French Geologic Society, and the Scientific Council of the French National Research Program. To the west, in the Tabuk area, Sarah Formation deposits fill narrow incised paleovalleys running north-south along Abdallah M.S. Memesh currently more than 30 km. The filling material generally consists of works as a Geologist at the BRGM "boulder-clays"-like siltstone at the base covered by massive Mapping Department. He received units of turbiditc sandstone. This succession resembles the his BSc from the Faculty of Earth succession of Sarah and Zarqa formations as it is described Sciences at King Abdul Aziz in Central Arabia. However, northwest of Tabuk, we University in 1993. Since 1994, he observed the superimposition and intersection of two has been involved in mapping successive incised paleovalleys, filled by similar lithologic projects of Phanerozoic rocks, sequence. Locally, dip-cavitation features occur below the especially in the Paleozoic strata of Sarah Formation. Such "karst-type" features dug into the north and northwest Saudi Arabia. Qasim Formation and can reach a depth of 80 meters west of Tabuk. In the same area extended networks of clastic dykes (approximately 50 km long) cuts the Paleozoic The Upper Ordovician Glacial-Related substratum, the development of such structures is interpreted to be in relation with glacial-related environment and Deposits in Northwestern Saudi Arabia: contemporary orientation of the regional field stress. New Data Dominique Janjou, Mohammed A. Halawani and Robert Dominique Janjou Wyns (see abstract "The Paleozoic Succession of the Tabuk Bureau de Recherches Géologiques et Minières Basin in Saudi Arabia: Lithostratigraphy, Sedimentology Mohammed A. Halawani and Sequence Stratigraphy" on pages 104-105 for Deputy Ministry for Mineral Resources, Jeddah biographies and photographs) Robert Wyns, Philippe Razin, Denis Vaslet Bureau de Recherches Géologiques et Minières Philippe Razin (see abstract "Sedimentology and Reservoir and Abdallah M.S. Memesh Geometry of the Late Permian Upper Gharif and Lower Deputy Ministry for Mineral Resources, Jeddah Khuff Formations in Interior Oman: Outcrop Study in the Haushi Area" on page 82 for biography and photograph) As a result of geologic mapping in the Tabuk Basin, the Late Ordovician glacial-related deposits were studied

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Denis Vaslet is employed by the al. (1988) chart. Subsidence rates during simulation were Bureau de Recherches Gèologiques kept constant, reflecting the uniformity of the sedimentology et Minières. He is responsible for the of the section for the 21 million years duration of deposition. cover rocks mapping project of the Carbonate rates increased from zero centimeter/1,000 years Saudi Arabian Directorate General at 300 meters, to 2 centimeters/1,000 years at 20 meters, to for Mineral Resources. He has been 12 centimeters/1,000 years at the surface. The Khuff involved in the complete litho- Formation has limited biostratigraphic age control, but stratigraphic revision of the coupling these ages with a sea level curve provides a method Phanerozoic rocks of Saudi Arabia, for dating its sequences. These sequence dates were tested particularly the lower Paleozoic. with the simulation and used to date the five informal Presently, Denis is currently in charge of the basic geology members of the Khuff Formation. The simulation suggests and geophysics department at the French Geological Survey that the Khuff E is contained within the Khuff D Member. which includes the program of geological mapping of France. Kurt W. Johnston is currently a PhD candidate at the University of South Abdallah M.S. Memesh (see abstract "The Paleozoic Carolina. His research is focused on Succession of the Tabuk Basin in Saudi Arabia: the Cretaceous sedimentary section Lithostratigraphy, Sedimentology and Sequence of offshore South Africa. Kurt is Stratigraphy" on page 105 for biography and photograph) currently interpreting the sequence stratigraphy of this area using seismic data supplied by Soekor. Kurt holds an MSc degree from Bayler Sequence Stratigraphy and Computer University of Texas. Simulation of the Khuff Formation (Late Permian-Early Triassic), Christopher G. Kendall is Professor Saudi Arabia and Other Gulf Countries of Geology at the University of South Carolina. He has worked extensively Kurt W. Johnston, Christopher G. Kendall in the oil industry and academia. His University of South Carolina research interests and publications and Ibrahim A. Al-Jallal have concentrated on the Arabian Saudi Aramco Gulf. Starting his career in carbonate sedimentology and petrology, The Khuff Formation ranges in age from Late Artinskian Christopher is interested in through the Scythian and consists of carbonates, evaporites sedimentary simulations and and minor clastic lithologies. These were deposited on a sequence stratigraphy with numerous publications on these broad, shallow shelf and lithologic facies include topics. siliciclastics, mixed evaporite carbonates and siliciclastics, restricted evaporitic carbonate shelf, shallow carbonate Ibrahim A. Al-Jallal has 17 years of shelf, organic reefal and argillaceous deep marine experience in the oil industry in Saudi carbonates. Sequence stratigraphy and a computer Aramco. His work experience varied simulation were applied to interpret the Khuff Formation. from basic development geology to complex reservoir geological studies In Arabia, the formation is divided from base up into the and predictions. His PhD thesis was siliciclastic Khuff E, and the carbonate/anhydrite Khuff D, on the Khuff Formation, its C, B and A units. It contains eight third-order sequences, depositional environment, reservoir six of which contain relatively thick accumulations of development, carbonate petro- anhydrite. Basal sequence boundaries are placed at the base physical characters with wireline of the anhydrite, which is interpreted to collect in lowstand logs and overall reservoir layering and characterization. systems tracts on the shelf. Not all of the sequences within Ibrahim recently extended his Khuff study to include the the Khuff Formation have this basal lowstand anhydrite. entire Arabian Plate to determine Khuff gas potential areas in the Gulf countries. Ibrahim is currently the Chief The Khuff sequences were simulated with Schutter's chart Geologist of Geological R&D at Saudi Aramco. Ibrahim is (personal communication) to simulate the Permian portion, a member of the Advisory Board of GeoArabia. while the Triassic portion was simulated using the Haq et

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Exploration Implications of Basin Modeling application, numerical basin modeling, and numerical and statistical techniques. After receiving his PhD from Boston Studies on Known and Potential Source University in 1976, he served on the faculty at Rensselaer Rocks in the Rub' Al-Khali, Polytechnic Institute and Bryn Mawr College. Jay has Saudi Arabia Using BasinFlow worked for Amoco and Getty Oil. He was an Editor and regular Columnist for GeoByte magazine, served as Peter J. Jones, Henry I. Halpern, Chairman of the AAPG Computer Applications Committee, William J. Carrigan, Saudi Aramco has been a keynote speaker for several major petroleum Jay E. Leonard, Marshall W. Titus industry functions, and has over 80 publications in refereed Platte River Associates journals. He currently advises in technology issues for Mohammad R. Al-Khadhrawi several oil companies. and Ibrahim A. Al-Ghamdi, Saudi Aramco Marshall W. Titus is a Senior Staff Major exploration and development efforts in the Rub' Al- Geologist with Platte River Khali of Saudi Arabia, have resulted in the need to revisit Associates, Inc. He has 15 years of the historical database with current geochemical techniques. basin modeling and petroleum These efforts are directed towards developing new exploration experience. Before exploration play concepts, as well as, refining the existing joining Platte River Associates in ones. Within the area of interest, known productive intervals 1993, Marshall worked with Shell on are found in the Lower Cretaceous and Jurassic. Potential hydrocarbon charge, basin modeling, and known source rocks in the area range from the and exploration projects in the Gulf Cretaceous to the Paleozoic in age. For example, the of Mexico and North Alaska. He Safaniya Member of the Lower Cretaceous Wasia Formation received a BSc degree in Geological Sciences from the is found to have intervals in excess of 100 feet with Total University of Texas at Austin in 1979 and his MSc degree in Organic Carbon (TOC) up to 9.6% and Hydrogen Indices Geology from the University of Houston in 1984. One- (HIs) up to 500 mg HC/gTOC. dimensional and multi-dimensional basin modeling as an application to remain his interest. Recent advances in basin modeling software facilitate modeling in one, two and two and one-half dimensions (map Mohammad R. Al-Khadhrawi (see abstract "Geochemical view). This approach allows the explorationist to integrate Evidence for Reservoir Compartmentalization in Central basin modeling studies throughout the area of interest much Arabian Paleozoic Reservoirs" on page 96 for biography more efficiently. These studies can then be used to formulate and photograph) the hydrocarbon charge history of the basin. Basin models, in this study, were constructed using Platte River Associates' Ibrahim A. Al-Ghamdi is an BasinView and BasinFlow software. Exploration Geologist working with the Exploration Organization in This study integrates a variety of geochemical and geological Saudi Aramco since 1985. He has data, in order to assess the source characteristics of various worked in area exploration, reservoir source rock candidates, as well as, the variation of thermal geology and wellsite, and in special maturation history for various source intervals throughout projects including reservoir modeling time. with Exxon in 1989. Most of his work concentrated on carbonates of the Peter J. Jones, Henry I. Halpern and William J. Carrigan Jurassic and the Cretaceous of Saudi (see abstract "Geochemistry of Eastern Saudi Arabian Arabia. Ibrahim is interested in carbonates, sequence Paleozoic Gas/Condensates" on pages 79-80 for biographies stratigraphy, artificial intelligence, geostatistics and field and photographs) geology.

Jay E. Leonard is President of Platte River Associates, Inc. He has over 25 60th EAGE Conference years experience in computer &Technical Exhibition technology, petroleum exploration, and technology transfer with 8-12 June, 1998 extensive experience with the For more information please contact: evaluation, development and EAGE Business Office utilization of petroleum industry P.O.Box 298 software. He also has experience 3700 AG Zeist, The Netherlands with database design and Tel: 31 30 696-2655; Fax: 31 30 696-2640

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A Conceptual Model for Super consistency in “Super-K” facies when the total body of data is examined. Core studies have indicated that there are Permeability in Uthmaniyah Field several lithotypes which exhibit extreme flow behavior.

Tom Keith, John C. Cole, Saudi Aramco Closer examination of core data reveals that although these Joerg E. Mattner, Sait I. Ozkaya lithologies are present in many of the “Super-K” zones, the and Kyle A. Waak,Western Atlas majority of occurrences of these lithologies do not exhibit extreme flow behavior and that in fact there are a wide range The Ghawar field has been subject to a high flow phenomena of rocktypes which, although permeable, are genetically known as “Super-K” since very early in its production unrelated to the oolitic grainstones and are not dolomitized. history. The term was originally coined by geologists and engineers working in the field to describe extremely high Tom Keith received his BSc degree flow confined to thin intervals usually on the order of 4 to 5 in Geology from the University of feet in thickness. A good working value for “Super-K” has Texas at Austin in 1976. He has been generally accepted as 500 barrel/foot/day. Initially, core worked with Saudi Aramco since studies and log data suggested a model in which a single, 1980 and has spent most of the time stratigraphically- controlled, facies was accountable for the on reservoir geology and geocellular vast majority of instances of extreme flow. Open fractures modeling in all of Saudi Aramco's intersected by the wellbore were held responsible for the eastern area fields. His most recent remaining cases. However, subsequent studies revealed efforts have been concerned with the more diversity in the stratigraphy, lithology, and flow impact of fractures on fluid flow in characteristics of the so-called “Super-K” facies than a the Ghawar Field. purely stratigraphic explanation could reasonably account for. John C. Cole has been with Saudi Aramco since 1991 where he is A conceptual model for “Super-K” is proposed in which Production Geologist specializing in the original stratigraphic model is integrated with a more 3-D modeling and reservoir pervasive vertical fracture system to explain the observed characterization. Between 1980 and diversity. Recent 3-D seismic and image logging results are 1986, John was with Texaco and then presented in support of the model and the potential impact joined BP International. He has of the model on other aspects of reservoir characterization worked in the North Sea, North Africa and management is discussed. and the Far East. He obtained a BSc in Geology in 1979 and an MSc in Recent image logging results in the Ghawar field supports Structural Geology in 1980 from Imperial College, London. a more significant role for fractures than had previously He is a member of CSPG, the AAPG and APEGGA. John is been suspected. Although a quantitative definition of the particularly interested in reservoir characterization of term has been put forth in a number of previous articles, its carbonates. actual occurrence is probably best described in qualitative terms. Its primary characteristic is simply confined flow Joerg E. Mattner and Sait I. Ozkaya (see abstract usually accounting for upwards of 60% of total fluid "Integrating Fluid Flow and Borehole Imaging Data in production within a few feet. The origin of the flow and the Fracture Characterization, Hanifa Reservoir, Abqaiq Field, geometry of the structures responsible play an important Saudi Arabia" on page 44 for biographies and photographs) role both in the short-term goal of designing water shut-off procedures to prevent premature breakthrough and in the Kyle A. Waak is a Senior Log Analyst planning of longer range drainage strategies. with Western Atlas Logging Services in Saudi Arabia where his primary Previous models put forth to explain this behavior have been responsibilities are interpretation of based on stratigraphic distribution of high permeability borehole imaging and magnetic dolomites and oolitic grainstones with fractures responsible resonance logs. He has held various for only a small percentage of high flow zones. Although engineering, sales, management and this serves to explain the wellbore characteristics of a high log analyst positions throughout his percentage of zones correlating with high flow, core career with Western Atlas in West description and log data suggests that there is sufficient Texas/Southeast New Mexico, the diversity in both the lithology and stratigraphy of “Super- Rocky Mountains and Venezuela. Kyle holds a BSc degree K” to bring a two-dimensional explanation into doubt. This in Petroleum Engineering from Texas A&M University and is especially true when the lack of areal correllatability of is a member of the SPE and SPWLA. “Super-K” is considered. Nor, do they explain the lack of

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Sedimentologic and Sequence Charles Kerans is a Senior Research Scientist at the Bureau of Economic Stratigraphic Framework of the Geology, the University of Texas at Shu'aiba Reservoir, Idd el Shargi Austin where he has worked since North Dome, Qatar 1985. Charles received his BSc degree in Geology from St. Lawrence Charles Kerans University in 1977 and PhD degree Bureau of Economic Geology in Geology from Carleton University The University of Texas at Austin in Ottawa, Canada in 1982. He served as a Senior Research Fellow The Aptian (Cretaceous) Shu'aiba reservoir at Idd el Shargi in Western Australia between 1982 and 1985 during which North Dome (ISND) was developed as a localized area of time he worked on Devonian reef complexes of the Canning shoal-water facies on top of a salt-rooted deep structure on Basin. In 1985 Charles joined the Bureau of Economic the Shu'aiba deep ramp. The stratigraphic model for the Geology’s University Lands Reservoir Characterization Shu'aiba reservoir at ISND developed here differs from many Program, focusing on Ellenburger and San Andres units of of the other Shu'aiba fields because it emphasizes the Permian Basin. From 1988 to 1991 he helped initiate depositionally controlled rock fabric changes rather than and directed the Bureau’s San Andres/Grayburg Reservoir diagenetic leaching at the post-Shu'aiba unconformity as a Characterization Research Laboratory (RCRL) and is primary control on reservoir quality. The integration of currently a Senior Research Scientist on the RCRL staff. modern sequence stratigraphic techniques of cycle hierarchy His research emphasis is on integrated reservoir definition and stacking pattern analysis, coupled with a characterization studies that utilize a sequence stratigraphic regional paleogeographic model, demonstrates the evolution framework. Currently, research is focused on developing of ISND from a sub-storm wave base deep ramp advanced sequence stratigraphic models for Cretaceous accumulation to an asymmetric shoal with distinct carbonate reservoir strata using outcrop data from Texas windward-leeward facies control at or just above fair- and subsurface data from the Middle East. Charles has weather wave-base. received several awards for best paper since 1988.

The Shu'aiba at ISND together with the Hawar shale represents one long-term (3rd-order?) 400-foot thick Origin of Limestone-Black Shales Bedding composite sequence that can be subdivided into four of Lower Carboniferous Limestone from (Shu'aiba D lowest, Shu'aiba A highest) symmetrical high- frequency sequences (HFS) that in turn are composed of Semnan Area, Central Alborz, North Iran small-scale high-frequency cycles. The Shu'aiba is dominated by mud-dominated rock-fabric facies with minor Kaveh Khaksar Orbitolina of deep ramp origin. Maximum flooding surfaces Geological Survey of Iran of the high-frequency sequences and selected cycle-base flooding surfaces define the main vertical heterogeneities The Lower Carboniferous (Tournaisian) marine strata in the in this reservoir and should be preserved in any layering Semnan area (eastern part of Central Alborz) consist of scheme that attempts to accurately represent fluid flow. limestone with black shale interbeds. The limestone-shale interbeds occur in a cyclic pattern. In the measured The upper portion of the Shu'aiba B HFS and the entire sequence, the limestone beds have an average thickness of Shu'aiba A HFS comprise the main reservoir interval at 30-40 centimeters and the black shale layers 10-20 ISND, the lower units being either in the water leg or of too centimeters. The maximum thickness measured is 58 low a reservoir quality. Detailed correlation of individual centimeters. The regular alternation of limestone with black high-frequency cycles throughout the field using logs and shale could have formed from a uniform primary sediment. facies descriptions from 15 cored wells allowed documentation of the last stages of evolution of this The mechanism responsible for the cyclical interruptions depositional structure. During deposition of upper 'B' cycles of limestone are most likely related to climate. This, in a general northwest to southeast thinning and deepening of turn, is influenced by the Earth's orbital perturbation through facies indicates minor syndepositional tilting to the fluctuations in the volume of polar ice, probably the northwest. Southeast tilting coupled with aggradation into immediate cause of these sedimentary cycles. Depositional fair-weather wave base during deposition of the 'A' resulted rates indicate that the bundles represent about 19,000 to in deposition of a shoal complex with a northwestern 23,000 years, corresponding to short precessional cycle. windward coral-rich rim and dasyclad-Orbitolina grain-rich cap that controls improved reservoir quality. Onlap by Bab facies shows no clear evidence of subaerial exposure or meteoric leaching.

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Kaveh Khaksar received his MSc New Insights to the Holocene degree in Geology from the University of Palermo, Italy in 1989 Carbonate-Evaporite Environments and PhD degree in Geology from the of Abu Dhabi University of Granada, Spain in 1994. Kaveh is a member of the Anthony Kirkham Scientific Board and Head of Reservoir Characterization, Scientific Communication and Research & Consulting, Inc. Scientific Services Office of Soil Conservation and Watershed Easier access to most parts of the Abu Dhabi coastline, Management Research Center and Expert of Geological combined with satellite imagery, has enabled a more detailed Survey of Iran. He has published more than 10 research examination of the Holocene strata than was possible twenty papers and scientific reports. or thirty years ago when the area was recognised as a key to understanding ancient, shallow marine, carbonate-evaporite environments. Whilst the basic principles of coastal progradations documented in those early days are still valid, Carbonate Faciolog from they portrayed an oversimplified picture of the Holocene Basic Openhole Logs coastal geomorphology and sabkha sedimentology. New data re-emphasises the importance of Miocene and Pleistocene Anwar S. Khalaf strata in forming antecedant topography which imposed Bahrain National Oil Company depositional complexity on the Holocene system. Former Holocene shorelines can now be mapped with greater clarity Defining carbonate facies from wireline logs has always and reveal its highly embayed nature. The Holocene been a very difficult task to achieve. This paper proposes transgressive limits are locally re-defined. Some palaeo- an easy approach for mapping the carbonate facies from the highs, that formed earlier Holocene peninsulas, have been most basic openhole logs, the Dual Lateralog and the completely removed by aeolian deflation. Contrary to what neutron-density logs. is commonly perceived from the literature, sabkha anhydrite does not occur as a continuous, widespread horizon. The conceptual modeling on which the methodology was Difficulties that many geologists have experienced in developed is based on the fact that the various carbonate locating anhydrite are largely due to there having been two facies will have different responses when logged by the distinct phases, but their distributions are now largely DLL-MSFL tool. Furthermore, these facies will have predictable by remote sensing. The later phase has different invasion profiles that would facilitate the task of historically formed a basis of idealised progradational mapping them. "sabkha cycles" and is indeed regressive, but the earlier and more abundant anhydrite is transgressive and compels Within each facies the relationship between porosity and geologists to more carefully consider depositional models permeability is directly proportional. In other words the involving peritidal evaporites. Relative sea level changes definition of the various facies from the wireline logs will and aeolian deflation have combined to impose a very high make the task of converting the log porosities into effective degree of complexity which would be difficult to understand permeability values relatively easy. The successful in such a thin stratigraphic interval in the subsurface. Apart application of the technique for characterizing the most from the world-renowned tidal oolite deltas formed seaward permeable facies in the Khuff Formation was completed and of the ebb tidal channels between barrier islands, Holocene the results were validated against the production profiles as tidal embayments also provided potential for oolite measured by the Production Logging Tool. The match development such as adjacent to the definitive "Evans line" between the two sets of results is excellent. near Abu Dhabi Island. A present day, analogous oolith factory is described from a tidal embayment in western Abu Anwar S. Khalaf is Manager of Dhabi. Exploration and Development at the Bahrain National Oil Company. Anthony Kirkham (see paper "Pleistocene Carbonate Seif Anwar graduated from Kuwait Dunes and their Role in the Development of Complex Past University with a BSc degree in and Present Coastlines of the U.A.E." on page 32 for Geology in 1976. biography and photograph)

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The Permo-Carboniferous Glaciogenics ‘Rahab’ lake systems. The oldest lake covered virtually all of South Oman (at least 340 by 150 kilometers), and reflects (Al Khlata Formation) of Oman: the major base-level rise associated with pronounced melting A Fresh Look at an Old Problem of any remnant ice caps/sheets. Good analogues for these lake systems can be found preserved in Quaternary Richard Knight and Christel Hartkamp-Bakker sediments from Scandinavia and North America. The Petroleum Development Oman youngest lake system was more fragmented, and developed into four localised depocentres (centred on Bahja, One of the key challenges that has faced oil exploration and Mukhaizna, Nimr and Dhiab). Overall the climate was production from the Permo-Carboniferous glacial deposits warming up dramatically (reflected in the establishment of (Al Khlata Formation) in South Oman, has been a cycad-prone land flora), prior to deposition of the overlying uncertainties associated with the distribution, evolution and Gharif Formation. stratigraphy of the Al Khlata Formation through time. A recent study, based on a network of 26 basin-wide correlation As a consequence of this study, there is a better panels, has attempted to address such issues. understanding of the genetic relationships and evolution of Biostratigraphical data have proved the critical element to the Al Khlata deposits in this region. This has allowed areas unraveling this unit: at present the sequence is divisible into to be risked and exploration initiatives/resources aligned 3 broad subunits (P9, P5 and the youngest P1), based on accordingly. palynology. Richard Knight graduated with a The oldest (P9) Al Khlata sequences clearly reflect a phase PhD in Palynology from of rapid sedimentation and high accommodation in South Southampton University in 1990. On Oman. The P9 unit is Late Carboniferous in age, and can joining Shell that year, he was exceed 100s of meters in total thickness. Climatically, this assigned to the Stratigraphy Section was a period of (in part) extremely dry, cool conditions. based in The Hague. In 1993 Richard The P9 landscape was highly irregular, with immense joined Petroleum Development contrasts in relief (‘U-shaped valleys’). These were probably Oman as an Operations Geologist, formed through an interplay of glacial erosion, salt and moved a year later to head dissolution/withdrawal and accentuated by rifting in the Exploration’s Palynology/Ops Neotethys. Sedimentologically, P9 sequences are Geochemistry Unit. He is now an Interpreter in North characterised by fluvial, deltaic, and minor glaciogenic Oman’s Frontier Gas Team. phases in deposition. Stacked outwash braidplain deposits (‘valley trains’) are prominent, regionally extensive features, Christel Hartkamp-Bakker (see abstract "The Karim and tend to occur towards the latter part of this period. These Oilplay: Cambrian Alluvial-Lacustrine Deposits in South- braidplain deposits herald the dawn of a major period of ice Central Oman" on page 97 for biography and photograph) advance.

By Latest Carboniferous/Early Permian times (P5), the topographic variation across South Oman was markedly The Challenge of South Oman’s diminished. The P5 period was one of extensive ice action, Athel Silicilyte as evidenced by widespread, cannibalised glaciogenics, and areas missing appreciable stratigraphy. Available floral data Stuart D. Lake, Pascal D. Richard, suggests that, at times, this was a relatively warm period, Muatsam Al-Raisi and Hannat Al-Hinai with high moisture levels. These observations probably Petroleum Development Oman relate to warmer interglacials. P5 sequences tend to be thin (<50-100 meters), highly sporadic in their occurrence and The Late Proterozoic, Early Paleozoic rift basins of South very difficult to correlate. Besides glaciogenics, localised Oman are filled with thick syn-rift salts. A Cambrian aggradational fluvial stacks and delta systems occur petroliferous rock has been found within these salt intermittently. sequences: the Athel silicilyte. It is both a source rock and a reservoir, and this unusual combination, combined with the Towards the end of the Al Khlata deposition (P1) in Early intra-salt setting, introduces significant challenges. The large Permian (Asselian/Sakmarian) times, the South Oman number of prospects and large proven in-place volumes have landscape was presumed to be virtually a level peneplain. the potential to significantly impact Oman’s hydrocarbon Localised deltas and isolated fluvial systems signified the resource base (both for oil and gas). final demise of ice activity in Oman. The latter is defined by a widespread, blanketing diamictite, which tends to Thick tight water-bearing petroliferous source rocks within directly underlie two regionally extensive, freshwater the Ara Group have been recognized since 1972 (Amal-1)

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along the shallow Eastern Flank of South Oman where the lithofacies, in combination with new seismic data, indicate salt seal has been removed by salt dissolution, however its that the Athel silicilyte could have been deposited in narrow reservoir potential was not recognized until 1989 when the northeast-southwest trending half-grabens (mini-basins) first Athel silicilyte oil discovery was made within the South within an active Cambrian rift system. These basins were Oman Salt Basin at Al Noor-1 fully encased in salt and controlled by reactivated basement faults which influenced overpressured. The promising, but low rates (44m3/d) of both intra-salt sedimentation and subsequent halokinesis. 48o API volatile sour oil led to further appraisal. After These former mini-basins (now positive “inverted” highs) establishing a stable oil rate of 100 m3/d (GOR 300 m3/m3 are locally modified by halokinetic processes. This structural

and 1.5% H2S in gas) from a recompletion on Al Noor-2 interpretation is confirmed and can be replicated by scaled (late 1994) 15 million m3 oil reserves were considered sandbox experiments and finite element modelling studies. proven with significant untested upside potential. The recognition of these “inverted” structures have allowed Subsequent appraisal wells and testing gave further the operator to plan seismic campaigns and to target wells encouragement to assess the potential of this new play more effectively. Since 1989, Athel Silicilyte has now been through an aggressive 15-well exploration and appraisal identified in 5 separate structures, of which three have campaign. significant hydrocarbon columns >200 meters (Al Noor 1, 2, 4, 5, 6; Al Shomou 1, 2, 3 and Marmul NW-7). Presently The reservoir is composed of an interbedded sequence of a Phase one pilot project is underway on the Al Noor field porous and non-porous (irregularly laminated micro- by drilling a series of development wells and a 1,500 m3/ crystalline silica and dolomitic cemented) silicilyte with an day surface facility. average layer thickness which is smaller than 1 meter.The average micro porosity is some 22 pu but the permeabilities However the Athel silicilyte still carries significant risks are very low, in the order of tens of micro Darcy. Given and technological challenges, including the need to improve these thicknessess/reservoir properties and the absence of sesimic data quality, find better reservoir, reduce costs and any reservoir analogues, extensive use of borehole imaging achieve a breakthrough in reservoir productivity, the new logs is made to unravel the reservoir sequences. model and new ideas being generated go a considerable way Geochemical analyses have established the Athel silicilyte to reduce the risks and to assess more fully the ultimate as a world class source rock; it is probably the source for potential of the Athel. much of South Oman’s oil. The entire unit is self-charged, being encased within thick Cambrian salt and lying at depths Stuart D. Lake obtained his PhD in between 2,500 and 5,000 meters. In areas where the salt Geology from Durham University in seal has been breached, the Athel oils have migrated to 1985. Stuart joined Shell in 1986 as shallower and younger rock formations. a Geologist and served in various assignments as a Geologist, Seismic Seismic data over much of South Oman was historically Interpreter and Team Leader with insufficient to map out intra-salt reflectivity or indeed even Shell companies in The Netherlands, to map top salt with any confidence. The combination of USA , United Kingdom and Egypt gravity data and long-cable seismic data (up to 10 before joining Petroleum kilometers) to improve imaging at depth led to the Development Oman in 1993 as Team identification of numerous intra-salt leads. The initial Leader Regional Studies. Stuart then joined the Frontier calibration of these leads was based upon their look-alike South Exploration Team as the Athel Theme Coordinator in nature to Al Noor, however the subsequent exploration 1996. He has recently become Team Leader for the North campaign has shown that this alone is not sufficient Netherlands Gas Team in the NAM. Stuart is a member of especially in areas in close proximity to carbonate platforms, the AAPG and PESGB and has published more than 10 areas of intense intra-salt imbriction or Western Margin technical papers on basin inversion, remote sensing, thermo- sourced intra-salt clastics. mechanical modeling, field and petroleum geology.

Regional geological data initially indicated that the silicilyte Pascal D. Richard (see abstract "Integrated Haushi facies of the Athel Formation was widespread in its Hydrocarbon Habitat Study in North Oman" on page 147 distribution. It was then believed that apart from the basin for biography and photograph) margin and a broad trend along the Birba High, where carbonate facies appear to occur, that much of the rest of Muatasam Al-Raisi obtained his BSc in 1991 from Penn the salt basin may contain rafts or slabs of silicilyte. The State University, USA. Muatasam joined Petroleum drilling campaign has shown that contrary to the original Development Oman in 1991 as Exploration Geologist before perception, the Athel is neither uniform nor regional in he obtained an MSc in Geological Sciences from the extent. Well data also make the complexity of the reservoir Colorado School of Mines in 1994. Muatasam is currently apparent, both from a static and a dynamic perspective. working as an Exploration Geologist with the Frontier South Patchy occurrences, variable thickness and associated Exploration Team. Muatasam has published papers on Sedimentary Geology.

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Hannat Al-Hinai received his BSc in Geophysics in 1988 Gregory Blokkeel is working on his from the University of Tulsa, and obtained his MSc in MSc degree in Applied Mathematics Petroleum Geology from Oxford Brookes University in 1994. and Mechanics at Bordeaux Hannat worked as Seismic Processor for Petroleum University, France. His research Development Oman from 1989 to 1993. He is currently interests are applied mathematics working with the Frontier South Exploration Team as a and combustion. Seismic Interpreter.

Inverse Stratigraphic Model for the Carbonate Production Estimation- Didier Granjeon is a Geologist in the Application to an Oman Outcrop Production Geology Group at Institut Français du Pétrole. He holds a Civil Saiida Lazaar, Gregory Blokkeel, Engineer's degree in Geology from Didier Granjeon and Dominique Guérillot Ecole des Mines de Paris and a PhD Institut Français du Pétrole in Geology from Rennes University, France. His research interests are This study is devoted to the numerical inversion of in the geosciences and deterministic stratigraphic model parameters. Our principal goal is to approach applied to 3-D basin identify the model parameters, such as the sediment supply modeling. (carbonate production) and the transport coefficients which control the way sediments are eroded, transported and Dominique Guérillot holds a PhD in deposited throughout the sedimentary basin. These Applied Mathematics from the parameters are related to a forward 3-D multi-lithologic University of Provence. He joined stratigraphic model. Our numerical study allows us to match Institut Français du Pétrole (IFP) in the real well data from the Oman carbonate platform. 1982 where he worked with the Reservoir Characterization Team. This work presents a semi-automatic inversion method He then became Project Manager for which is an extension of the one presented at GEO'96 and "Fluid Flow in Heterogeneous in GeoArabia, 'Three-Dimensional Carbonate and Reservoir". Dominique is currently Siliciclastic Forward Modeling', v. 1, p. 144, 1996 where the Director of the Geology and the identification of the carbonate production was realized Geochemistry Research Department at IFP. His areas of via a trial-and-error method. professional interest are in applied mathematics and physics, modeling in geoscience, reservoir engineering and To illustrate the method, this study will involve numerical characterization, fluid flow in heterogeneous porous media, results of the forward and the inverse model in a mono- numerical simulation, up-scaling and inversion methods, lithological case. The inverse model corresponds to and software development. optimization techniques using a gradient descent method which minimizes the difference between model predictions and observations. Interpreting Regional Seismic Amplitudes Saiida Lazaar joined the Geology in a Central Saudi Arabian and Geochemistry Research Sandstone Reservoir Department of Institut Français du Pétrole after completing her PhD. Jia J. Lee, Ahmed M. Al-Otaibi, Her research interests are numerical Maher I. Al-Marhoon and Daniel S. Evans analysis, sedimentary basin Saudi Aramco modeling, inverse methods, turbulence, fluid mechanics and the A relatively shallow sandstone oil reservoir was recently design and implementation of wavelet discovered in Central Saudi Arabia. Regional seismic fast algorithms for solving some amplitudes mapped through the reservoir from 3-D RAP numerical problems. Saiida holds a PhD in Applied stack data volume were found to be characterized by large Mathematics from the University of Provence, France. amplitude variations and trains of high amplitude pockets.

Exploratory drilling based on amplitude bright spots showed some initial success. However, results of further drilling

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found little correlation between the high amplitude zones strategies depend heavily on reservoir type and associated and hydrocarbon accumulation. A study through seismic facies. 3-D geological modeling studies are currently modeling and inversion was carried out to investigate the underway for several large fields in order to improve our occurrence of high amplitude anomalies and their understanding of reservoir architecture and uncertainties. It implications for hydrocarbon potential in the area. While is planned to extend these studies to cover all fields in the porosity was shown to be the dominant factor for amplitude area. behaviors, it takes combined effects from porosity, tuning and the fluids to create the observed high amplitudes. Characterization of depositional facies from conventional Modeling of seismic amplitude in zones with known porosity log data, which is one of the key issues to enable the was shown to provide indications of optimally tuned sand construction of robust 3-D geological models, remains a thickness, hence presence of potential reservoir-quality sands challenge. An integrated regional study has been carried in the area. The modeling results were also compared with out to improve our regional depositional facies model for observations inferred from inversion study. Pre-stack the Gharif reservoir. This has involved interpretation of all amplitude analysis as a function of offset, along with other Gharif borehole images (approximately 25 wells), attribute analyses, were also examined but were found less description of all Gharif cores (1,350 meters) in the area, diagnostic for amplitude patterns in the study area. and the search for appropriate outcrop analogues. The Al Khlata study is currently more limited to borehole image Jia J. Lee is currently Geophysical interpretation calibrated with core data. This paper Specialist with the Geophysical summarizes the results of the borehole image analysis study Department of Saudi Aramco. He is carried out by Petroleum Development Oman (PDO), involved with special seismic Schlumberger and Western Atlas in 1997. processing and integrated studies of exploration problems. Prior to A step-by-step approach is used to identify and interpret joining Saudi Aramco in 1992, Jia structural dip, lithology, ‘borehole image lithofacies’ and was with ARCO for nine years ‘tentative borehole image facies’ from high resolution image engaged in seismic exploration and data. Lithological description is derived from conventional development on worldwide prospects. open hole log data using a multivariate histogram technique. He received his MSc in Geophysics from Columbia The lithological boundaries are adjusted against the high University and a PhD from Penn State University. resolution image data. Bedding planes are interactively picked from the geological workstation image, allowing Ahmed M. Al-Otaibi (see abstract "Recent Discovery identification of structural dip, irregular lamination, soft Confirms Stratigrahic Trap Potential in the Permian sediment deformation, foresets, set boundaries and bed Unayzah Formation of Central Saudi Arabia" on page 92 boundaries. Both lithological description and bedding for biography and photograph) information is used to derive the ‘borehole image lithofacies’. Tentative ‘borehole image facies’ (i.e. channels, Maher I. Al-Marhoon (see abstract "Application of Multi- crevasse splays, sheetfloods, etc.) are then identified using Seismic Attributes in Estimating Reservoir Properties" on criteria proposed by the PDO geologists based on calibration page 52 for biography and photograph) with core interpretation.

Daniel S. Evans (see abstract "Recent Discovery Confirms Results of the study comprise interpreted genetic reservoir Stratigrahic Trap Potential in the Permian Unayzah elements with paleo-current indications for use in 3-D Formation of Central Saudi Arabia" on page 92 for geological modeling, structural dip for structural mapping biography and photograph) and quantification of the present day horizontal in situ stress for reservoir fraccing. Future work includes further integration of core and outcrop studies to refine the criteria used in depositional facies interpretation and to provide a Integrated Borehole Image Analysis better interpretation of paleo-current indications. In addition as Input to 3-D Modeling a neural network approach may also result in a more reliable interpretation. Xavier Y.A. LeVarlet, Peter Audretsch and Stuart K. Arnott Acknowledgments: The authors would like to thank H. Petroleum Development Oman Koelemij (PDO), O. Schoenicke (Schlumberger), J. Mattner, I. Ritters and L. Qobi (Western Atlas), K. Higgs and J. Approximately half of all the oil produced in the Bahja- Thompson (Robertson) for their contribution. Rima area of Central Oman (25,000 m3/d from 33 fields) is derived from glacial and fluvial Al Khlata and Gharif reservoirs of Permo-Carboniferous age. Field development

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Xavier Y.A. LeVarlet is a graduate A detailed 3-D reservoir geological model of the Haima and of the Ecole Nationale Supérieure du Al Khlata formations at Runib field was constructed using Pétrole et du Moteur (Institut GEOCAP Shell software. The latest seismic interpretation Français du Pétrole) in Rueil and petrophysical data were used in the study. The 3-D Malmaison, France. He joined Shell reservoir models consist of complex geometries of Al as a Production Geologist in 1994. Khlata-filled valleys and Haima pods. The 3-D models were Following an initial assignment in used to assess the distribution of reservoir properties within Oman Xavier spent two years at the flow units and to prepare input data for the reservoir KSEPL before joining the Production simulation study. Although the full range of geological Geology Section of NAM’s Business uncertainties was investigated, at the end only the most likely Unit Oil in 1991. He was posted back to Petroleum model was provided for the dynamic modeling. Development Oman in 1996 as a Production Geologist in Central Oman with an active participation in 3-D geological The static geological model was upscaled and transferred reservoir modeling studies. into the dynamic model using Shell’s proprietary Reduce and MoReS software. Full field and key single well history Peter Audretsch received a BSc in matches were obtained to provide confidence in the Geology from the University of simulation model. Only modest modifications to the Calgary, Canada in 1982. Between geological model were required. The dynamic model was 1982 and 1992 he worked as an then used to evaluate the evolution of Equivalent Oil Column Exploration Geologist for Petro- with time, which in a heavy oil environment with bottom Canada working on Western water drive, is used to plan development and infill wells. Canadian and International ventures. Furthermore, the model was used to assess the best In 1992 Peter joined Shell development strategy to arrive at the most favorable International and was posted to economics. Petroleum Development Oman in Exploration. Peter is currently Production Geology Section The main results of the integrated study are: (1) the 3-D Head in the Bahja-Rima area Development team. geological model results in a better understanding of 3-D geometry of flow units and the reservoir property distribution Stuart K. Arnott is currently a within the flow units; (2) the main geological uncertainties Production Geologist with Petroleum were evaluated; (3) a more economical field development Development Oman, working mainly strategy has been generated; and (4) reserves have been on 3-D modeling of fluvial Gharif matured. reservoirs. He previously worked for Shell in Holland and Britoil in the Acknowledgments: Authors would like to thank D. Adenuga U.K. Stuart holds a BSc in Physics/ and A. Al-Shamaki for their contribution. Geology from the University of Glasgow and a PhD in Seismology Xavier Y.A. LeVarlet (see abstract " Integrated Borehole from the University of Durham. Image Analysis as Input to 3-D Modeling" on this page for biography and photograph)

Runib Field: A Fit-for-Purpose, Integrated Joniek I. Hage obtained a MSc degree in Physics from the Free 3-D Static and Dynamic Modeling Study University of Amsterdam and a PhD in Natural Sciences from the Xavier Y.A. LeVarlet, Joniek I. Hage University of Leiden. He joined Shell and Patrick van Daele in 1991 to work in KSEPL in drilling Petroleum Development Oman engineering research for two years, improving kick detection systems. The Runib field in Central Oman has produced 3 million Joniek then moved to reservoir m3 of oil from the glacial and fluvial Haima and Al Khlata engineering to work on improved reservoirs of Palaeozoic age. Current net oil production is recovery processes in naturally fractured reservoirs. He 1,300 m3/day at 82% BSW mainly from horizontal wells. was posted to Petroleum Development Oman in January The estimated field STOIIP is 30 million m3. The oil is 1997 as a Reservoir Engineer of the Bahja/Rima area where viscous (20¼ API) and is produced by a strong bottom/edge he is currently responsible for the development and water drive. Booked ultimate recovery is 6 million m3. An operational reservoir engineering aspects of fields with a integrated study has been carried out with the aim of widely varying range of properties. optimising the field development strategy and maturing additional reserves.

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Patrick van Daele obtained an MSc concession area has been split-up into four separate MEGA in Geology from the University of 3-D-grids according to the dominant acquisition direction. Louvain, Belgium, on the subject of Within each MEGA a consistent inline and crossline clay mineralogy. He joined Shell in numbering is used and the data is stored in cubes of 10 by 1993 and has since been working in 10 kilometers. Processing of newly acquired seismic will Bangladesh, Tanzania, Oman and follow the same procedures, meaning that it will be easy to Nigeria in the Exploration and build up new even bigger MEGA projects as new data Production function as a Geologist and becomes available. Seismic Interpreter. He is currently the Senior Production Seismologist The seismic data of the Megacells is on-line available on a in Petroleum Development Oman, looking after acquisition, high density mass data storage system, and thus facilitates processing and interpretation of 3-D projects in South Oman. fast data loading and efficient project definition and project management on the interpretation workstations.

The 3-D Megagrid in PDO: A 3-D Data This poster elaborates further on some practical aspects of the Megagrid concept, and highlights several benefits of such Management Concept for Seismic an approach for processing, workstation support and seismic Processing, Workstation Support interpretation. and Interpretation Maarten Ligtendag graduated in Maarten Ligtendag 1988 in Applied Geophysics from the Petroleum Development Oman Faculty of Mining Engineering at and Luppo Kuilman Delft University of Technology. He Saga Petroleum (previously Shell International) joined Shell International in 1989 and worked as a Seismic Processing The concession of Petroleum Development Oman (PDO) is Geophysicist at Shell Expro, London covered with some 30,000 square kilometers of 3-D seismic until 1993. After a one year posting data, consisting of some 90 individual surveys, acquired and to Shell Australia working in seismic processed since 1984. With the 3-D coverage rapidly data processing, Maarten was growing, more and more continuous coverage over large transferred to Petroleum Development Oman to take up the parts of the PDO concession was established. Traditionally, position as a Seismic Processing Controller. surveys were processed on a survey by survey basis, each with their own seismic datum, incorporating some data of Luppo Kuilman (see abstract "The Karim Oilplay: neighboring surveys wherever possible. This approach Cambrian Alluvial-Lacustrine Deposits in South-Central resulted in patchwork of, often overlapping, stand-alone 3- Oman" on page 97 for biography) D projects all with different datums, amplitude normalizations and processing histories (reflecting the continuous improvements made over the last 13 years in 3- Geostatistical Porosity and Permeability D processing and acquisition technology). Modeling Using 3-D Seismic and Log Data, PDO strongly believes in the value of large integrated A Carbonate Reservoir Example interpretation projects and the information that can be gained by using them. The commitment to follow up on this strategy Tien-when Lo, Chris W. Grant can be illustrated by the most recent major project (3-D RC Squared Consulting MEGA Project) from the processing department addressing Bill Keyser and Thomas Chen PDO’s 3-D database as described above. Texaco Inc.

As part of the 3-D MEGA Project all individual seismic The objective of this project is to assess the risk of drilling a surveys acquired to date in the PDO concession area have series of horizontal wells by building and analyzing log scale been merged. Processing issues addressed were: re- (1-foot resolution) 3-D porosity and permeability models datuming of the seismic data according to the two new constrained by 3-D seismic data and log data. standard seismic datums defined for North and South Oman (replacing the 15 different datums previously in use), Porosity and permeability models were built with the amplitude normalization between the various 3-D surveys, following steps: (1) Generate high resolution 3-D impedance and phase correction (all data is now zero-phase). The model with stochastic seismic inversion. The stochastic

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seismic inversion algorithm used in this project is a full Sonic Data While Drilling waveform stochastic inversion. It uses sonic and density logs as hard data and 3-D seismic data as soft data. Instead Increases Drilling Precision of using a finite number of seismic attributes to guide the inversion, it builds an impedance model that will recreate Richard Logan and Ron Deady the full 3-D seismic data. Since this algorithm honors the Halliburton Energy Services full waveform, it theoretically honors all the seismic attributes. (2) Generate high-resolution porosity models with Technology has recently been developed in logging while co-located cokriging, using porosity logs as hard data and drilling (LWD) that provides a significant new aid to the impedance model generated in the previous step as soft geological steering during drilling. The LWD sonic tool data. Because the correlation between porosity and provides real-time data that is used to correlate seismic data impedance varies within the field, this project used a with drilling data. The tool uses a two-transmitter, four- correlation coefficient map, instead of a single correlation receiver array to measure acoustic waveforms and determine coefficient. (3) Convert porosity models to permeability compressional and shear wave slowness in subsurface models with "cloud transform". This cloud transform is formations. Besides transmitting essential data to the surface based on a cross-plot between core permeability and log in real-time, the device also stores more complete data in porosity. downhole memory for later retrieval and further analysis.

After building a series of equally probable porosity and The real-time data is used to generate a synthetic seismogram permeability models, the risk of drilling certain wells can for immediate refinement of the geological model upon be assessed. The drilling engineers specified certain drilling which the drilling program is based, thereby helping improve constraints and defined several well trajectory criteria. A precision in well-steering. The real-time data can also be series of virtual wells were "drilled" through the porosity used for timely estimation of pore pressure, contributing and permeability models. Each virtual well is then ranked potentially important safety information for the drilling based on the pre-defined well trajectory criteria. operations.

The predictions made by these virtual wells were shortly This paper will give a brief overview of the new technology confirmed by real wells. This accurate prediction is probably and will focus on its application to drilling operations. Field due to the fact that the high-resolution porosity and examples will be presented demonstrating the applications. permeability models are realistic, and they reflect true reservoir heterogeneities. Richard Logan is a Technical Specialist, LWD Drilling Systems, Tien-when Lo is Manager of Seismic Applications with RC with Halliburton Energy Services in Squared Consulting. He received his PhD in Geophysics Houston. He received a BA degree from Massachusetts Institute of Technology in 1988. From in Chemistry from the University of 1988 to 1996, he was with Texaco Exploration and Missouri and has 20 years experience Production Technology Department. He joined RC Squared in the petroleum industry. Before Consulting in 1997. His principal interests are seismic joining Halliburton, Richard held inversion, stochastic reservoir modeling, and reservoir various field, technical sales, management. marketing, and management positions with Schlumberger and Inteq Chris W. Grant has been a Research Geologist with Chevron throughout North America. He is a member of the SPE, and has been involved in the fields of stratigraphy and SPWLA and AADE. geostatistics. He received a BSc in 1985 from California State University and an MSc from Long Beach State Ron Deady is a Subject Matter University in 1991 in Geology. Chris was the recipient for Expert with Halliburton Energy the Outstanding Thesis award in the School of Physical Services in Houston. He holds a BSc Sciences in 1991. He is interested in areas such as degree in Geology from Northern Quantitative Reservoir Modeling and Sedimentation and Illinois University. Before joining teaches Chevron's basic and intermediate Geostatistics Halliburton, Ron held various field courses. and staff positions with Anadrill Schlumberger and Baker Hughes Bill Keyser and Thomas Chen - biographies and Inteq. He is a member of the SPE and photographs are unavailable. SPWLA.

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Exploration Scale Structural Controls on years, Tony has been the Staff Carbonate Specialist for Chevron Carbonate Ramp Trends: New Insights Overseas Petroleum assisting in the from the Kuwait-Saudi Arabian Coast exploration and development, of the Northern Arabian Gulf description and characterization of and Northern Yucatan, Mexico carbonate plays and reservoirs worldwide. Tony has conducted Anthony J. Lomando many Carbonate schools and Chevron Overseas Petroleum seminars for Chevron, its partners and associates in Russia, New observations on wave dominated ramps from the Kazakhstan, Mexico, Congo, Angola, China, Kuwait, the Kuwait-Saudi Arabian Coast of the northern Arabian Gulf U.K. and U.S. He has authored over 40 papers and abstracts and the northern Yucatan, Mexico, indicate that exploration dealing with all aspects of carbonate exploration and scale facies distribution trends are strongly influenced by reservoir management and is an associate editor of the structure. AAPG Bulletin and the Journal of Sedimentary Research.

Wave dominated ooid rich Holocene and modern ramp deposits from the southern Kuwait-northern Saudi Arabia The Application of Modern Carbonate coastal regions provide a complimentary model to the classic tide-dominated ramp system of the Trucial Coast, United Depositional Systems in Arab Emirates. Orientation of the Kuwait coastline parallel Reservoir Geostatistics to prevailing northwesterly Shamal wind direction, as opposed to perpendicular in the UAE, appears to be the main Anthony J. Lomando, Henry A. Legarre control on tide versus wave- dominated systems. The and Eberhard Gischler locations and trend orientations of strand plains, sabkhas, Chevron Overseas Petroleum and channels are related to fold noses which trend perpendicular to the coastline. Our industry continues to become more reliant on geostatistics and reservoir simulation to provide critical The northern Yucatan Ramp extends from the Holbox barrier information for sound business decisions. Spatial island complex on the east for over 300 kilometers to the geostatistical analyses of modern systems provides insights Chicxulub impact crater site (K/T boundary impact site) in into reservoir characterization for simulation. Spatial the west. The major longshore transport along this skeletal- variograms from modern data sets can provide constraints dominated ramp is east to west. This is provided by a and guidelines for spatial distribution of reservoir properties northeast prevailing wind direction which impinges on this (porosity, permeability, saturation, etc.) that can significantly microtidal system at an oblique angle and the Yucatan current increase the accuracy of reservoir simulations. which flows east to west as it passes from the Caribbean to the Gulf of Mexico. Long barrier island trends protect Reefs and reef margins on carbonate platforms are well lagoons that vary from normal marine to hypersaline. Barrier studied but the vast majority of reserves in oil and gas island styles, relative positions on strike and lagoon character reservoirs are stored in platform interiors and, until now, change with changes in location of fault/fracture zones and our detailed knowledge of these systems was poor at best. regional arches. Four modern isolated carbonate platforms from the Belize- Yucatan Province of Central America were studied. Each In both cases, exploration and reservoir scale trend platform example represents different types of flow units geometries are not linear with changes in characteristics and barriers common in carbonate fields. The results provide controlled by synsedimentary faults, folds, and fracture critical insights into models for reservoir flow unit zones which control antecedent topography and subsidence. architecture and heterogeneity. These geometries are repetitive and, therefore, predictable if extended to applications in the Jurassic and Cretaceous The Lighthouse and Chinchorro platforms are grainstone- of the Middle East especially in the search for stratigraphic packstone dominated with abrupt facies partitioning and traps. pronounced facies anisotropy and serve as models for high energy grainstone reservoir flow units. The Glovers Anthony J. Lomando completed his graduate studies in Platform interior is dominated by over 850 patch reefs 1979 at the City University of New York where he worked surrounded by wackestone to grainstone sediments and on the Jurassic ramp carbonates of the U.S. Gulf Coast. serves as an example of a very heterogeneous isotropic flow The next eight years were spent in exploration and unit. The Turneffe Platform is characterized by mud- development in the Permian Basin and the Jurassic and dominated lagoons punctuated by channels and sparse patch Cretaceous systems of the Gulf Coast. For the past nine

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reefs. Turneffe serves as an example of an intra-reservoir Rock Fabric Approach to Petrophysical barrier or baffle but highlights critical regions in reservoir flood situations where cross flow might be expected. Quantification of Geologic Descriptions: Shu'aiba (Middle Cretaceous) Reservoir, The Chinchorro Platform provides a representative example Idd El Shargi Field, Offshore Qatar of how this process works. Full platform analyses provides a set of anisotropy orientations and ranges that could be F. Jerry Lucia used to distribute properties of a single flow unit. Bureau of Economic Geology, Subdivision of the platform into subareas show distinctly The University of Texas at Austin different directional trends and also some differences in range characteristics. The importance is that it is an areally A key step in constructing a reservoir model is the conversion continuous data set that allows for unlimited variation in of descriptive geological interpretations to numerical sample size for testing geostatistically significant spatial engineering data. In this study of the Shu'aiba reservoir, distributions of a variety of properties. Idd el Shargi field, offshore Qatar, quantification of geologic descriptions is accomplished through fundamental rock- Anthony J. Lomando (see abstract "Exploration Scale fabric/petrophysical relationships. The Shu'aiba reservoir Structural Controls on Carbonate Ramp Trends: New in the Idd el Shargi field, has been characterized by three Insights from the Kuwait-Saudi Arabian Coast of the rock-fabrics based on core and thin section study. Most of Northern Arabian Gulf and Northern Yucatan, Mexico" on the reservoir can be characterized as an Orbitolina page 121 for biography and photograph) microporous wackestone to mudstone (type 3). Toward the top of the reservoir, fabrics are pellet wackestones and pellet Henry A. Legarre is a Research grain-dominated packstones (type 2). Algal and coral Geologist on the Geostatistics Team allochems are abundant in some areas near the top of the at Chevron Petroleum Technology reservoir forming a mud-dominated or grain-dominated Company in La Habra, California. packstone fabric. These allochems have been dissolved to Prior to his current assignment, he form grain molds. Microfractures in the lime-mud matrix was a Development Geologist with connect the molds and produce a touching-vug pore Chevron USA. Previously employed geometry (type 1). Each rock-fabric has a unique porosity- by Scripps Institute of Oceanography permeability transform. Microporous wackestone is the and Woods Hole Oceanographic poorest reservoir rock. As the lime-mud becomes more Institution, Henry’s research has pelleted the porosity-permeability relationships improve. involved organic and inorganic geochemistry, clay The combination of microporosity, moldic pores, and mineralogy, hydrogeology, clastic, diagenesis, and surface microfractures produces an additional improvement in ocean biogeochemical processes. He received his MSc permeability. The microporosity is believed to be the result degree, with distinction, from San Diego State University, of mineralogical stabilization and compaction of lime-mud. in Geological Sciences. Molds of algal and coral allochems are evidence for dissolution and most likely result from dissolution of Eberhard Gischler received a BSc unstable aragonite and reprecipitation of stable calcite degree in October 1984. In February cement during burial. The microfractures that connect the 1991 he received a PhD in Geology moldic porosity are suggested to have formed by collapse and Paleontology. After receiving his during burial. PhD, Eberhard took a two-year post- Doctoral position at the University Rock-fabrics types 1, 2, and 3 can be identified by cross- of Tübingen followed by two years at plots of water-saturation, porosity, and reservoir-height. For the University of Miami to study a given porosity and height, water-saturation increases from modern carbonate environments of type 1 to type 3. Quantification of the saturation model for Belize and Florida. During his time rock-fabric type 3 was accomplished through analysis of at the University of Miami, Eberhard worked on the sixteen capillary pressure curves. Excellent matches Holocene sediments facies and development of the Belize between the saturation model and Archie saturations were atolls Glovers Reef, Lighthouse Reef, and Turneffe Islands obtained for microporous wackestone intervals in crestal and also studied the condition of reefs and reef-building wells using a zero-capillary-pressure level of 5,300 feet. corals in south Florida and the Bahamas. Currently Higher Archie than model saturations where found in flank Eberhard is an Assistant Professor of Geology at the wells, and may result from increased clay/organic content University of Tübingen, Germany. on the structural flanks.

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Rock-fabric-specific porosity-permeability transforms are (1) Well to seismic data calibration: This step is very used to calculate permeability, and the resulting permeability important for extracting a wavelet ensuring a good tie profiles match well with core analysis. The vertical between the synthetics at wells, from logs, and the permeability profiles form the basis for construction of a 3- neighboring real traces. A methodology based on multi-well D permeability model of the Shu'aiba reservoir. multi-trace calibration is applied to ensure the extraction of a robust and stable wavelet over the entire study area. This F. Jerry Lucia is a Senior Research wavelet is used for stratigraphic deconvolution followed by Fellow at the Bureau of Economic picking of the main seismic events. Geology, The University of Texas at Austin. He acquired a BSc degree in (2) 3-D post-stack stratigraphic inversion with a priori Engineering in 1952 and MSc degree information: Geological information is introduced in the in Geology in 1954 from the inversion process by means of an a priori impedance model. University of Minnesota. His This model is built by interpolation of impedance logs, at technical expertise includes origin wells, in a manner that honors the geometry of correlation and distribution of carbonate strata, surfaces defined from picked seismic horizons and petrophysics, and petroleum geology. depositional knowledge. The inversion algorithm is based Before joining the Bureau on 1985, he was a Consulting on a full 3-D scheme that allows the integration of vertical Geological Engineer for Shell Oil Company assigned to the as well as lateral seismic information in both inline and cross- Head Office. Jerry retired in 1985 with 31 years experience line directions, thus ensuring a high degree of spatial as a Geological Engineer with experience in research and consistency. The resulting acoustic impedances are another operations. He is currently co-principal investigator of the step towards the lithologic interpretation of seismic Characterization Research Laboratory. Project areas amplitudes. include the Permian Basin and the Middle East. He has received awards for Best Paper from AAPG Wallace E. Pratt (3) Application of statistical pattern recognition techniques Memorial in 1994 and 1995 and Distinguished Service for providing a geological interpretation of the inversion Award from West Texas Geological Society in 1993. Jerry is results: The translation of seismic-derived acoustic an active member of the AAPG, SPE, and the Society of impedances into geological properties of the reservoir is not Sedimentary Geologists, and is a Fellow in the Geological simple, because of the limited seismic bandwidth and Society of America. indirect relationship. Thus, a statistical interpretation is proposed with a methodology that combines seismic attributes with supervised and unsupervised pattern Improved Characterization of the recognition techniques. The interpretation is based on the detection of variations of the seismic character within a time Unayzah Reservoir, Central Arabia, from window corresponding to the reservoir interval. Techniques 3-D Seismic with Stratigraphic Inversion such as cluster and discriminant analyses are employed to and Statistical Pattern Recognition statistically classify the seismic character into seismic facies. One strong point of the methodology is that uncertainties in Costas G. Macrides, Ahmed M. Al-Otaibi, the interpretation are quantified through computation of Marty Rademakers probabilities of assignments to the various facies. The final Saudi Aramco seismic facies maps with their accompanying uncertainties Claude Blanchet, Pierre-Yves Déquirez maps are powerful for predicting the reservoir lateral and Frédérique Fournier variations, and thus defining new well locations, and/or new Institut Fran•ais du PŽtrole prospects.

3-D seismic provides crucial information for better reservoir Costas G. Macrides received a BSc characterization, particularly in highly heterogeneous in Physics from the University of depositional environments. This is the case for the Unayzah Athens in 1980, a MSc in Geophysics fluvio-deltaic sandstones where limited well control is not in 1983 and a PhD also in sufficient for defining the reservoir behavior in the interwell Geophysics in 1987 from the areas. However, lithostratigraphic interpretation of seismic University of Alberta. He has been data should incorporate geological knowledge for better an Assistant Professor at the constraining the interpretation and ensuring the consistency University of Manitoba and a Senior of all available data. This paper demonstrates a joint Research Geophysicist with Seis-Pro application of stratigraphic inversion and pattern recognition and Consultants in Calgary. Costas to a 3-D data set covering an area of 500 square kilometers joined the Geophysical Research and Development Division over the Unayzah reservoir in Central Arabia. The main of Saudi Aramco in 1993. His interests include seismic steps are described as follows:

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tomography, refraction statics, AVO and multi-component Français du Pétrole (IFP) in Rueil- seismology in oil exploration. He is a member of the SEG Malmaison, France. She worked as and EAGE. a Research Geophysicist for Elf Aquitaine Production between 1985 Ahmed M. Al-Otaibi (see abstract "Recent Discovery and 1990 before joining IFP. Confirms Stratigraphic Trap Potential in the Permian Frédérique received degrees from Unayzah Formation of Central Saudi Arabia" on page 92 Ecole Nationale Supérieure de for biography and photograph) Géologie de Nancy in 1983, and from Ecole Nationale Supérieure du Marty Rademakers is a Geophysicist Pétrole et des Moteurs in 1985. She with the Area Exploration holds a PhD degree from Institut National Polytechnique Department of Saudi Aramco. Prior de Lorraine. Her current interests include multivariate to joining Saudi Aramco in 1996, statistics, geostatistics, signal processing and seismic Marty worked with Templeton Energy interpretation for reservoir characterization. (1981-1983); LASMO (1983-1992); and Plains Resources (1992-1996). He received a BSc in Geology from Plio-Pleistocene Clastic Reservoirs State University of New York in 1978 of the Offshore Nile Delta, and an MSc in Exploration Geophysics from the University of Tulsa in 1981. Arab Republic of Egypt

Claude Blanchet has worked for Steven J. Maddox, Neil Hodgson, John L. Swallow, Institut Français du Pétrole (IFP) in Elizabeth M.M. Loudon and Kambeez Sobhani Rueil-Malmaison, France for 35 British Gas years. She is currently Geoscience Technician with the Reservoir In the last few years, a prolific new gas play has been Seismic Group. She previously had discovered and exploited in the offshore Nile Delta, Egypt. been working with the Remote British Gas is a leading player, with three large operated Sensing Group of IFP. Claude's concessions in the southern Mediterranean Sea. current interests include signal estimation well to seismic calibration Although this play is phenomenally successful (with an and stratigraphic inversion. almost 100% success rate), it is challenging for exploration and development/production, due to the shallow, Pierre-Yves Déquirez is currently a undercompacted and unconsolidated nature of the reservoirs. Research Geophysicist with the The shallow and unconsolidated sands are however, ideal Reservoir Seismic Group of the for observing direct hydrocarbon affects on seismic, a fact Geophysical Division at Institut which has contributed greatly to the amazing success rate. Français du Pétrole (IFP) in Rueil- Malmaison, France. He is also The reservoirs are very young (Plio-Pleistocene), and are involved in reservoir studies and only circa 0.5-4 million years in age. They are generally applies IFP’s post-stack inversion quite unconsolidated and undercompacted and sand tools to basins worldwide in production during testing is common. Coring is a also a cooperation with various petroleum challenge and to date competitor operations have had mixed companies. Before joining the Reservoir Seismic Group, success. Pierre-Yves worked for three years with the Marine Acquisition Team of IFP, dealing with on-board data In addition to the above problems, the reservoirs are variably acquisition quality control softwares. Pierre-Yves is a pressured, depending on environment of deposition, graduate of Institut de Physique du Globe de Strasbourg reservoir connectivity and depth. In general, the Plio- and of École Nationale Supérieure du Pétrole et des Moteurs Pleistocene is normally to slightly overpressured, (1983). He is a member of the EAGE, and his main areas of particularly in the shelfal areas. Abnormally pressured sands interest are integration of surface and borehole data, and have been encountered by competitors however (eg. seismic data processing and interpretation for reservoir ca.13+ppg sands at <1,800 meters) and these pose a characterization. significant well control and design problem. These overpressured sands appear to be either isolated deeper Frédérique Fournier is currently Leader of the Reservoir marine sands, or sands in communication with deeper Seismic Project in the Geophysical Division of Institut pressures via faults.

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The pressure regime is also important in reserves estimation Kambeez Sobhani has over 25 years as it impacts on the formation volume factor, leading to under oil and gas company experience in or over estimation of volumes if the correct pressure regime Iran and the UK. He worked for is not prognosed. BNOC/Britoil and Hamilton Brothers on a variety of projects, before joining Steven J. Maddox has worked as a British Gas in 1988. Kambeez has Geologist in the oil and gas industry worked as a Petroleum Engineer, but for nearly 10 years with British Gas is currently Principal Petrophysicist E&P and British Petroleum working on a variety of assets in Italy, Exploration. Prior to this he gained the Middle East and North Africa. a BSc degree from the University of Other experience includes UK Continental Shelf and Hull in England and a PhD from the Southeast Asian oil and gas projects. University of Edinburgh, Scotland. Steven has worked extensively on hydrocarbon exploration and Stylolites and Related Features: development in the North Sea and Atlantic Margin, and internationally in Southeast Asia, North Africa and the Their Implications on Near-Wellbore Middle East. Flow Behavior, Examples from Arabian Gulf Reservoirs Neil Hodgson has worked as a Geologist in the oil and gas business Joerg E. Mattner and Sait I. Ozkaya for over 10 years with British Gas Western Atlas International E&P and British Petroleum Exploration. He graduated from the Stylolites are the result of solution processes found in University of Manchester and carbonate rocks. In the Arabian Gulf region, extensive and received a PhD from the University pronounced stylolitisation is observed in many hydrocarbon of Leicester. Neil worked in the UK reservoirs. These phenomena are commonly associated with Continental Shelf with BP prominent tension gashes, brecciation, and cemented zones. Exploration and BG E&P, before Such features, in conjunction with the stylolites, cause becoming Exploration Manager for British Gas in Cairo, changes in the near-wellbore flow regime. High resolution Egypt. image logs, production logs and core examples are utilized to demonstrate the wide spectrum of features and their effects John L. Swallow has worked as a on fluid flow. Geophysicist in the oil and gas business for over 15 years with the Joerg E. Mattner and Sait I. Ozkaya (see abstract British Geological Survey, Total Oil "Integrating Fluid Flow and Borehole Imaging Data in Marine and British Gas E&P. He Fracture Characterization, Hanifa Reservoir, Abqaiq Field, graduated from the University of Saudi Arabia" on page 44 for biographies and photographs) Leeds and has worked on the UK Continental Shelf and was posted with Total for several years in Venezeula. Since joining British Gas, Unbiased Target Prediction he has worked primarily on Egypt and is now sub-surface Using Global Seismic Inversion team leader for exploration at British Gas’s head office in the UK. Kim G. Maver, Helle Wagner ¯degaard A/S Elizabeth M.M. Loudon graduated and Clare N. Baldock with a BEng in Electro-Mechanical Digicon Geophysical Ltd. Engineering from Aston Univeristy in 1992 and an MSc in Petroleum A 3-D seismic survey acquired in offshore Abu Dhabi has Engineering from Imperial College been processed by Digicon Geophysical Ltd. and seismic London in 1993. Elizabeth joined inversion for acoustic impedance has been performed by British Gas in 1993 and has worked ¯degaard A/S. as a Petroleum/Reservoir Engineer on a variety of Egyptian and UK A potential carbonate reservoir is encountered by three Continental Shelf assets. She has wells. The seismic data associated with the potential also worked in Egypt for the ZAFCO Petroleum Company. reservoir exhibit a substantial variation indicating a non- homogenous reservoir.

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The aim of the seismic inversion project is to predict the data environments. In the last 7 years, she has specialized lateral variations of the target zone without biasing the final in land data processing, with emphasis on work acquired in results. This is possible by using the ISIS seismic inversion the Middle East. Clare is currently supervising the technique, which is not constrained by well logs or a detailed processing of a large, complex transition zone survey for starting model. As the method is a 3-D multi-trace global Abu Dhabi Company for Onshore Oil Operations and optimization technique, it is furthermore very robust towards partners, together with several other land and marine noise. projects from the Middle East.

By performing seismic inversion, acoustic impedance data are obtained. The acoustic impedance data are easier to interpret and give better information about lateral variations In Search of the Precambrian/Cambrian in lithology compared with the seismic data. Furthermore, Boundary in the Huqf the acoustic impedance data can be correlated directly with Sedimentary Rocks, Oman the well logs. Since the well logs are not used directly in the seismic inversion process, the results can be verified by Margaret McCarron comparison with the well logs. For this project, the well University of Oxford logs show a near optimal match with the acoustic impedance results verifying the validity of the seismic inversion. The Huqf Supergroup is deposited on rifted Pan-African basement. The rift basin was infilled with a thick diamictite The acoustic impedance results indicate substantial lateral unit and overlain by a 12-meter thick cap carbonate. Further variation in the thickness of the target zone and the acoustic sagging enabled the deposition of two siliciclastic/carbonate impedance variations within this zone may furthermore be units before a second episode of rifting began with the indicative of substantial variations in reservoir quality. subsequent deposition of the Ara/Fara Formation. Granodiorite dykes beneath the diamictites give a Rb/Sr date Kim G. Maver graduated in 1989 of 554±10 million years (Dubreuilh et al., 1992) while from Copenhagen University with a Cloudina fossils have been found in the Ara Formation MSc in Geology and in 1996 with a indicating a Vendian to Tommotian age for the Ara. A Pb/ PhD in Geology. Kim is currently the Pb date 529±16 have also been acquired from Birba Deputy Managing Director of carbonates (PDO unpublished data). Thus an Infracambrian ¯degaard A/S. He has worked 5 age for the Huqf Supergroup is inferred. years for the Danish Geological Survey as a research assistant Detailed sedimentological studies, including biostratigraphy specializing in seismic modeling. For in conjunction with stable isotope geochemistry the last 4 years he has worked for (chemostratigraphy), is presently being carried out with a ¯degaard A/S specializing in seismic modeling and seismic view to elucidating the position of the Precambrian/ inversion. Cambrian boundary. Skeletal fossils to confirm age are missing owing to hypersaline conditions in Oman which Helle Wagner graduated in 1993 prevented its colonization by index skeletal fossils and trace from Copenhagen University with a fossils. However, putative fossil markings have been found MSc in Geophysics and in 1997 with above the cap carbonate within the Masirah Bay Formation, a PhD in Geophysics. Helle is which are comparable with those found in Ediacarian rocks currently employed as an Inversion elsewhere. Specialist in the consultancy department at ¯degaard A/S. Before Carbon isotopes show negative-positive peaks at two places working with ¯degaard A/S, Helle within the succession. A pronounced negative peak is worked on her PhD, the topic being possibly correlative with the feature "W" recognized at the global seismic inversion. Precambrian/Cambrian boundary in Mongolia, Siberia, Iran and the "N" interval recognized in Namibia, Spitsbergen Clare N. Baldock graduated in 1982 and northwest Canada. Preliminary strontium isotope data from the University of Bath with a indicates a trend toward more radiogenic values throughout BSc in Physics and Geophysics, and the sequence which is comparable with trends seen in other is currently the Senior Geophysicist reference sections but differs in being isotopically heavier. responsible for data processing at This problem is currently under investigation. Digicon Geophysical Ltd.’s processing centre in Abu Dhabi. She has 15 years seismic data processing experience from a wide variety of

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Margaret (Gretta) McCarron is The main changes between 1996 and 1997 are: currently studying for a D.Phil at the University of Oxford. The Huqf 1996 sequence: Supergroup in Oman is the subject of - F/K filter, 1750m/s, fully tapered, 48dB attenuation her research, which includes the - two gate, single trace gapped DBS sedimentology of surface exposures - 1s or 2s trace scaling pre- and post-stack in Central Oman and the Oman - multiple attenuation with initial velocities Mountains. She is using stable - DMO velocity analysis isotope geochemistry to define the - DMO and stack chronostratigraphic framework of the - migrate Supergroup. Gretta graduated from Queens University, - phase only deabsorption and zero-phase Belfast with a BSc (Hons.) in 1995. 1997 sequence: - F/K filter, 1750m/s, 30% flat, 48dB attenuation From Noise Attenuation Towards - phase and amplitude deabsorption, maximum 24dB boost Signal Preservation - zero-phase - single gate, single trace gapped DBS Andrew McGinn, Erik Kleiss and Rini M. Klaassen - angle consistent scaling Petroleum Development Oman - surface consistent scaling - DMO, pre-stack output Petroleum Development Oman (PDO) processes in-house - multiple removal after final velocity analysis approximately 4,200 square kilometers of new 3-D and 3,800 - stack kilometers of new 2-D land data per year acquired with - migrate vibroseis. The seismic processing has historically been targeted at structural plays and has concentrated on noise The 1997 sequence is considered to be the first stage in the and multiple attenuation. development of more controlled processing. Preliminary work has already indicated that the DBS can be replaced by However there are potential exploration and production a residual deconvolution which takes into account the objectives where amplitude control, increased temporal and deterministic wavelet manipulation performed. It is also the spatial resolution, together with a stable phase wavelet would intention to perform this residual deconvolution in a surface be beneficial. Therefore the processing methodology has consistent manner. Work is also ongoing to modify or even been examined in an attempt to perform more deterministic completely remove the K/F filter. rather than statistical processing and to concentrate on signal preservation and phase stability rather than noise attenuation. All test processing has been carried out with ShellÕs SIPMAP processing package. Compagnie GŽnŽrale de GŽophysique's The new processing sequence which has been developed software is then tested in order to emulate the required steps, can now achieve our goals. Numerous reprocessing trials and if necessary modifications are requested. on 2-D and 3-D data have conclusively demonstrated that major gains can be achieved by following the methodology The 1997 sequence can be implemented in all production and all new data in PDO can now be processed in this processing. The angle consistent scaling was essential before fashion. The deterministic approach, with suitable flexibility the surface consistent scaling became stable. Previous to handle low S/N ratio data, will be presented, together attempts at surface consistent scaling failed due to the with examples of the resultant data quality. inherent amplitude decay on the records, so that a solution for amplitudes at one time level either over or under In the past, performing ÔdeterministicÕ processing was not compensated the amplitude behavior at other levels. considered viable for PDOÕs data, the emphasis was on noise control with strong K/F filters (sometimes in both shot and Unfortunately data quality does not allow all seismic data receiver domain) and several passes of trace scaling. to be treated in this manner. Therefore prior to DMO the Changing the emphasis to wavelet and amplitude surface consistent information is analyzed to determine if preservation meant that the processing sequence would the S/N ratio is too low for such techniques to succeed, in follow a similar sequence to that employed on marine data which case scaling or filtering is employed to stabilize the within Shell. Namely, Earth deabsorption and signature noise present, resulting in a loss of relative amplitude deconvolution, but coupled with a more rigorous surface information. consistent amplitude scaling than commonly used on marine data.

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The more deterministic processing sequence has already 3-D Land Acquisition Geometry: demonstrated its value with broadband, relative amplitude data being delivered to the interpreters. As well as the direct What is the Best Compromise Between benefits from de-absorption, zero-phasing etc, subsequent Cost and Quality? steps i.e., statics and velocity analysis improve. Poor data areas where the full surface consistent scaling approach is Julien Meunier, Jean-Jacques Postel, not valid, still benefit from the new wavelet manipulation. Michel Denis and Claude Vuillermoz Compagnie GŽnŽrale de GŽophysique Andrew McGinn is a senior geophysicist with Shell International If cost and turnaround time were irrelevant, we might all E&P, currently working in Petroleum agree that the ideal 3-D acquisition geometry would be a Development Oman (PDO) in disk centered on the source-point. The radius of the disk seismic processing QA. Prior to his would be wide enough to include all the reflected energy. posting to PDO in September 1996, The source and receiver geometry would be isotropic (disks), Andrew supervised acquisition and and the station interval would be the same in both the X and processing of seismic data in a Y directions. Finally, the source interval would be the same variety of locations for the Shell as the station interval (in both the X and Y directions). Group. He has 17 years geophysical experience and holds BSc and PhD degrees in Mathematics In a conventional Common Mid-Point approach, such a from the University of Southampton. geometry would result in 4 families of bins, all with the same offset distribution and with an azimuth distribution Erik Kleiss joined Shell in 1985, rotated 0°, 90°, 180° and 270°. However, to make cost leaving Delft University of savings, this ideal geometry would be impaired in 3 ways: Technology where he obtained a PhD (1) spatial sampling of the disk; (2) reduction in its shape; in Reactor Physics. Until 1990 Erik and (3) source and receiver pattern anisotropy. All of these worked in the Experimental Seismic will have a negative impact on the final seismic image. Processing group in the Shell E&P research laboratory in Rijswijk, Spatial sampling: Most 3-D designs use different sampling Holland, on a variety of subjects, the intervals in the in-line and cross-line directions; source and last few years being engaged in receiver grids are defined by station and line intervals. The setting up 3-D depth migration. average station density is inversely proportional to their Thereafter he went to Warri in Nigeria as 3-D Processing product. It may not be the same for the cost. Geophysicists and filled positions in Port Harcourt as Section Head Contractor Processing and as Head of Seismic The station interval is usually twice the bin size. It is chosen Processing. In 1994 Erik moved to Petroleum Development short enough to avoid spatial aliasing. The line interval is a Oman as Head of Seismic Data Processing. major parameter of the acquisition foot print. It defines the number of families of bins with different offset and azimuth Rini M. Klaassen graduated from distributions. Due to processing limitations, the variation in HTS Vlissingen as an Electrical these distributions results in the distortion of the amplitude Engineer in 1974 and joined Shell in and phase of the average seismograms in each bin. 1978. After spending four years in experimental processing in KSEPL Reduction in shape: Besides the awkwardness of a disk and following Wetenschappelijk geometry in a marine environment, recording all the stations Reken courses at the Delft University, within a circle around a land shotpoint requires a very high Rini moved to Oman as a Seismic number of recording channels. The disk is more often than Processor and was later transferred not changed into a rectangle and acquisition symmetry is to SIPM were he was involved in both therefore reduced. The consequences of this reduction land and marine 3-D processing. He is currently team leader depend upon the seismic conditions (weathered layer of the SIPMAP seismic processing group in Petroleum variations resulting in static anomalies, presence of ground Development Oman. roll, multiple reflections, anisotropy, complex tectonics).

AAPG Annual Meeting Moreover, in order to reduce station deployment costs, 17-20 May, 1998 several source-points are recorded through the same receiving patch. This reduction results in an increase in the For more information please contact: number of bin families with different offset azimuth AAPG Conventions Department distributions. Tel: (918) 560-2679; Fax: (918) 560-2684

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Source and receiver anisotropy: For various reasons, it is Claude Vuillermoz is the Chief impractical to use isotropic arrays. Though it is sometimes Geophysicist for Compagnie possible to use a single source-point and a single receiver- Générale de Géophysique (CGG). point, it is more usual to use linear arrays. This simplification His interests are focused toward the will make source-generated noise - and, to a lesser extent, various applications of modern reflected signal - more dependent upon azimuth. seismic, particularly 3-D, repetitive 3-D, 3-D-3C, AVO, Inversion, as After a theoretical analysis detailing the first two previous essential elements for reservoir points, this paper will compare the response of ten 3-D characterization and integrated geometries, first on a flat geology, and second on a diffracting reservoir studies. Claude has spent point. Although we cannot claim to obtain a firm answer to his entire 29-year career with CGG, where he has been the title question, a correlation between theoretical signal- assigned to various positions in acquisition, processing and to-noise ratios and cost estimate ratios for different 3-D interpretation. From 1964 to 1974, his experience with CGG geometries will be analyzed, and trends deduced. included operations in Europe, Indonesia, Africa, Canada as Party Chief, supervisory and technical management. Reducing costs is certainly a very reasonable requirement From 1974 to 1976, he was Processing Center Manager in when designing a 3-D acquisition geometry. It is also Gabon, Africa. From 1976 to 1981, he was Processing desirable to evaluate the risk associated with the Center Manager in Calgary, Canada. From 1981 to 1989, corresponding departure from the ideal geometry. Such an he was Chief Geophysicist for North America and evaluation can be performed prior to acquisition using such Processing Center Manager in Denver, Colorado. From an analysis. 1989 to 1992, he was R&D Manager of North America, in Houston, Texas. Claude holds a MSc degree from the Julien Meunier is R&D Geophysicist University of Lyon, a PhD degree in Geology from the with Compagnie Générale de University of Grenoble, an Engineering degree from Géophysique. He graduated from the ENSPM, the post graduate School of Petroleum at Institut Institut Polytechnique in 1971. Français du Pétrole in the exploration branch. He has Julien's professional interests are 3- contributed to numerous publications and is a member of D seismic acquisition and processing. the SEG, EAEG, AAPG, DGS and HGS.

Source Rock Distribution and Thermal Maturity in the Jean-Jacques Postel is currently Southern Arabian Peninsula Research and Engineering Manager - Land and Shallow Water Acquisition Penelope Milner with Compagnie Générale de Phillips Petroleum Company Géophysique. He graduated from Ingenieur Ecole Centrale de Lyon in The purpose of recent work in the southern Arabian 1978. Jean-Jacques' professional Peninsula has been to investigate the source potential of interests are seismic acquisition deeper horizons such as the Paleozoic. A variety of newly methods and equipment, seismic drilled and older wells together with exclusive and non- processing. He is a member of the exclusive reports have been used in order to develop new SEG, EAGE and AFTP. maturation and migration models for newly emerging plays, and to develop a better understanding of the subsidence and Michel Denis is currently Area maturation history of a large and diverse area. Geophysicist with Compagnie Générale de Géophysique. He It has been possible to conduct comprehensive burial history received a PhD degree in modelling for a number of Oman, Saudi Arabia and the Mathematics from the University of United Arab Emirates wells. This, together with modelling Paris in 1978. Michel is interested of hypothetical wells derived from structure maps has in 3-D processing and 3-D design. improved our understanding of oil and gas-prone source He is a member of the SEG and rocks for Cretaceous, Jurassic and Paleozoic strata. The EAGE. resultant maturity distribution has been developed with the aid of a robust structural model for the southern Arabian Peninsula.

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In tandem with this study, available core and cuttings data geology of the area, maturation and burial history, and the have been analyzed to measure total organic content, local and regional heat flow regimes. maturity and pyrolysis parameters using proprietary techniques. The rock evaluations have been used to The pre-Khuff clastic sandstone facies in southern onshore supplement the existing database and to map source rock Abu Dhabi, area C, is comprised of fluvial deposits in quality. The proprietary artificial intelligence program contrast to eolian sands in the offshore area. Significant ÔSource Rock AdvisorÕ has been used to evaluate some of textural and petrographic variations are evident between the these rock samples, and the data input, evaluation, and results two sandstone facies. The fluvial deposits are fine- to obtained will be demonstrated on a laptop computer. medium-grained, poorly sorted with markedly poor reservoir quality due to silica dissolution, feldspar alteration, Integration of source rock quality and maturity maps bioturbation and the presence of authigenic clay minerals. resulting from this study has improved regional On the other hand, the dune foresets facies of the eolian understanding of Oman, Saudi Arabia and the United Arab sands reflect a better sorting and higher quartz-grain ratio Emirates. It is planned for this work, together with reservoir with an overall favorable petrophysical characteristics. distribution studies, to assist in the process of acreage acquisition in the Middle East. Regional heat flow modeling and burial history analyses clearly indicate that the pre-Khuff clastics and their potential Penelope Milner obtained a first hydrocarbon content in the Shah area were subjected to much degree in Geology and second degree higher temperatures than in the offshore area. Intense in Geophysics in the early 1980s. physical conditions of temperature and pressure have placed After a short position with a seismic these sediments and any possible hydrocarbon content below contractor she joined Phillips the gas generation window and possibly into the metagenesis Petroleum Company in 1984. stage in the Shah area. Penelope's assignments have included a lengthy spell in the North Awad A. Mohammed is a Staff Sea on the Southern Gas Basin Geologist with Abu Dhabi Company Hewett Field development, and also for Onshore Oil Operations (ADCO). on regional “Yet-To-Find” studies in the Central Graben. Prior to joining ADCO in 1991, In the last two years she has led a UK-based team reviewing Mohammed was with United Arab Middle East potential. She has presented papers previously Emirates University (1990-1991) and at the 1993 Society of Petroleum Engineers conference and with the Chevron Companies from at the 1995 UK Landmark Users Conference. 1979 to 1989. He has a BSc (Honors) in Geology (1979) and received his MSc and DIC in Petroleum Geology Geological Constraints on the from Imperial College, London in 1983. Mohammed is a Pre-Khuff Hydrocarbon Prospectivity, committee member and Assistant Secretary of the Society of Explorationists in the Emirates and is a member of the South-Central Onshore Abu Dhabi AAPG.

Awad A. Mohamed Abu Dhabi Company for Onshore Oil Operations Fracture Identification Using Borehole The term pre-Khuff clastics is conventionally used to Acoustic Measurements in describe the Late Carboniferous to Permian non-carbonate Crystalline Rocks: A Case Study sediments, unconformably underlying the Permian strata. These clastics were found to be hydrocarbon-bearing in Saad Hassan Mohamed offshore Abu Dhabi, area A. However, they are devoid of Belayim Petroleum Company significant hydrocarbon shows and have not warranted and Ehab A.R. Negm testing so far in onshore Abu Dhabi. Halliburton Energy Services

Integrated well data were analyzed from four wells located Recent developments in borehole acoustic measurements in a profile running from southern onshore Abu Dhabi to have led to improved evaluations of fractured formations. the south, to area B in offshore Abu Dhabi to the north. Different techniques analyzing the effect of fractures on The reservoir diagenesis, rock facies and depositional travel time and acoustic wave from amplitude were used, environments were delineated, and appreciable differences and the resultant changes due to rock deformation were that favored the reservoir quality in the offshore area are interpreted in terms of position, orientation, density, and recognized. In addition, the study investigated the regional production potential.

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Data derived from acoustic measurements in a lower Eocene The Upper Jurassic (Najmah) fractured limestone in East Belayim field, Sinai, Egypt, were analyzed in terms of fracture delineation and potential flow Hydrocarbon System of West Kuwait zones. A Circumferential Acoustic Scanning Tool for borehole imaging measurements was used to measure the Leonard V. Moore, Deborah Gilbert position and orientation of fractures in the borehole. 2-D Exxon Exploration Kuwait Inc. and 3-D gray-scale and colour image maps covering 360 Alaa Al-Ateeqi and Yousef Al-Zuabi degrees of the borehole were studied in terms of changes in Kuwait Oil Company both ultrasonic travel time and amplitude. Anomaly, discordance, and high amplitude sinusoidal waves were The prospectivity of the Upper Jurassic hydrocarbon system marked, natural fractures were distinguished and their of West Kuwait has been defined based on the results to orientation, density, and effectiveness for productivity date of a joint technical study between Kuwait Oil Company described. Full Wave Sonic tool measurements were run in and Exxon Exploration Kuwait Inc. The primary goal of compressional, shear and stonely modes. Compressional this study is to define the potential for light oil similar to the and shear wave slowness was analyzed to measure the stress Kra-Al-Maru (KM-1) discovery, which tested 49.5° API oil field around the borehole. Stonely and shear wave slowness, from the Najmah Formation. This requires stratigraphic along with the density data, were used to identify areas of definition of the oil prone source facies within the Najmah, possible fractures and permeability based on the Stonely/ mapping the areal extent of these facies, maturation/ elastic Stonely resemblance technique. Stonely wave migration timing, drainage fill and spill modeling, and trap slowness measurements were subjected to amplitude, timing. reflection and energy loss analysis techniques to identify fractures zones. Open hole porosity measurements were Detailed sequence stratigraphy of the Upper Jurassic section used to delineate potential flow zones. in West Kuwait identified eight distinct depositional systems tracts based on core and log analysis. Sampling of cores The output from all tools were correlated and fractures were from these units for source potential (Total Organic Content, delineated, studied and confirmed. Other correlation was RockEval and thermal maturity) identified source-rich carried out with gas chromatography and mud logs and their highstand and transgressive systems tracts with up to 19% usefulness is assessed for use in the study. This paper uses original TOC and HI's over 700 mgHC/gmC interbeded with a case study to emphasise how we may use acoustic non-source to poor quality source rock facies. Oil extracts measurement to study fractured formations and evaluate from selected source-rich core samples have been correlated their production potential. to reservoired Najmah oils at Kra-Al-Maru, Minagish and Umm Gudair. Saad Hassan Mohamed graduated from Cairo University. He is Interpreted well logs have been tied to regional 2-D seismic currently working with Belayim across West Kuwait and to 3-D surveys at Minagish field Petroleum Company's Log Analysis and the Kra-Al-Maru discovery area. These data sets, along and Petrophysics Division. Saad with well-specific burial history and thermal models have worked on Wellsite and Operations defined a prospective area for light oil in West Kuwait. In Geology in the Gulf of Suez and Nile addition, datumed seismic horizons tied to migration timing Delta. He was seconded to IEOC to derived from modeling studies, and overlain by drainage work in the Qantara area. Saad is flow lines indicate the light oil at Kra-Al-Maru arrived within well-experienced in the latest the last 10 million years, from basinal area to the north and wireline logging and logging while drilling techniques northeast. To the south-southeast, along the greater Kra- including computer- based formation evaluation. He is a Al-Maru Trend, there is an increasing risk for discovering member of the Society of Professional Well Log Analysts. indigenously generated heavier oils.

Ehab A.R. Negm graduated with a Leonard V. Moore is a Senior Diploma in Applied Geophysics from Exploration Geologist with Middle Cairo University in 1987. He is East Venture Development, Exxon currently Senior Log Analyst for Exploration Company in Houston, Logging and Perforating with Texas. He has over 20 years of Halliburton Energy Services in international experience including Egypt. Ehab also worked with Gulf postings to London, Singapore, of Suez Petroleum Company as Bangkok and Dhahran, Saudi Arabia. Petrophysicist in the Exploration His specialization is in source rocks Department between 1987 and 1991. and hydrocarbon systems analysis. He is a member of the Society of Professional Well Log Analysts.

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Leonard holds degrees in Geology from the University of deformation involving the high-angle reverse faults is Connecticut and Southern Methodist University in Dallas, interpreted as Early Tertiary, implying that pre-Permian Texas. strata and Permian-through-Upper Cretaceous strata exposed in the Saih Hatat and Jebel Akhdar anticlines were Deborah Gilbert received BSc and arautochthonous (uplifted over the reverse fault, but not MSc degrees in Earth Sciences from displaced laterally a far distance) in this deformation event. Adelphi University in New York. She The allochthonous Hawasina and Sumeini sedimentary rocks has worked for Exxon Exploration and the ophiolite complex are interpreted to have been Company and its various affiliates emplaced onto the platform carbonate in the Late Cretaceous since 1977 focusing on regional oil, and to have also been arautochthonous during the Early source and maturation studies in the Tertiary deformation. The interpretation also indicates a Gulf of Mexico, southeast Asia, major Late Paleozoic compressional event affecting the pre- Eastern Europe, the former Soviet Permian section exposed in the cores of the Saih Hatat and Union and the Middle East. Jebel Akhdar anticlines.

Alaa Al-Ateeqi (see abstract "Impact of 3-D Seismic Surveys The southern portions of the Saih Hatat and Jebel Akhdar on Minagish and Umm Gudair Fields Development, Kuwait" structural cross-sections extend into the northern Ghaba Salt on page 42 for biography and photograph) Basin and the northern part of the Musallim High, respectively. As constrained by subsurface well and seismic Yousef Al-Zuabi is currently a Senior data, the pre-Permian section in the Ghaba Salt Basin Geophysicist with Kuwait Oil consists of a thick (>4 kilometers) sequence of Cambrian- Company. Yousef has 12 years through-Silurian, predominantly non-marine-to-shallow experience in petroleum and marine, clastics (Haima Supergroup). In contrast, out of exploration activities. He received the Ghaba Salt Basin, in the Musallim High region, the his BSc degree in Geology from Haima Supergroup is generally less than one kilometer thick, Kuwait University in 1985. and interpreted to thin to the north. The fundamental difference in the pre-Permian strata exposed in the cores of the Saih Hatat and Jebel Akhdar anticlines is the thick (>3.4 kilometer) section of Ordovician age shallow marine strata (Amdeh Formation) present in the Saih Hatat anticline, but absent in the Jebel Akhdar anticline. In our interpretation Regional Structural Style of the Central the thick shallow marine clastics exposed in the Saih Hatat anticline represent the northern extension of the Early Oman Mountains: Jebel Akhdar, Saih Hatat Paleozoic Ghaba Salt Basin, which has been uplifted over a and the Northern Ghaba Salt Basin high-angle reverse fault in the Early Tertiary deformation event. The cross-section through Jebel Akhdar is located to Van S. Mount and Roderick I.S. Crawford the northwest of the Ghaba Salt Basin, along the Musallim ARCO International Oil and Gas Company High, and therefore, the thick sequence of Ordovician strata was not deposited and is not observed in the Jebel Akhdar A pair of regional, north-south trending, structural cross- structure. sections over the Saih Hatat and Jebel Akhdar anticlines in the central Oman Mountains have been constructed based Van S. Mount received a BA degree on surface, well, and seismic data. The cross- sections extend in Geology from Hamilton College to the south to include the northern end of the Ghaba Salt and PhD in Structural Geology from Basin and the northern portion of the Musallim High, Princeton University. He joined the respectively. The incorporation of subsurface data from Structural Geology Research Group south of the Oman Mountains into the cross-sectional at ARCO Exploration and Production interpretations have important ramifications regarding the Technology Company in 1989 where structural style of the Saih Hatat and Jebel Akhdar anticlines, his work concentrated on quantitative and differences in the pre-Permian section exposed in their analysis and interpretation of cores. complexly deformed prospect-scale structures. Van is presently at ARCO International Oil and Large-scale structural geometries observed on the cross- Gas Company where he is working as an Exploration sections suggest that the Saih Hatat and Jebel Akhdar Geologist in the Middle East Exploration Group. anticlines are basement-involved compressional structures, underlain by north-dipping, high-angle, blind, reverse faults located beneath their southern limbs. Latest compressional

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Roderick (Rod) I.S. Crawford graduated from the University of VSPs and 3-D Seismic Pitfalls at Wales with a BSc in Geophysics. Shaybah Field, Saudi Arabia Initially he was employed in seismic acquisition and processing at Edgardo L. Nebrija, Saudi Aramco Geoteam Ltd., UK, later moving into and Bernard G. Frignet, Schlumberger seismic interpretation. As a Consultant he specialized in mapping The 3-D seismic data at Shaybah field does not reveal a structurally complex areas. He clear reflector at the top of the target ShuÕaiba reservoir. joined ARCO British Ltd. in 1991 Furthermore, its synthetic seismic response varies areally where he has continued to work challenging exploration while several intra-reservoir reflections observed on the 3- and development projects. Presently Rod is seconded to D data cannot be confirmed on the synthetics. Two causes the Middle East New Ventures and Operations Group, ARCO have been suspected: (1) contamination of the 3-D data by International Oil and Gas Company. residual multiple noise; and (2) editing/environmental effects on the Shaybah density/sonic logs. Hence, the reservoir structure map is based on picks made on a consistent reflector closest to the reservoir, the top of the Biyadh Formation at Hydrocarbon Accumulations Associated the base of the ShuÕaiba. with Halokinesis in the Marib-Shabwa and Tihama Basins of Yemen Since acquiring and processing the 3-D seismic data, sonic and density have been logged from total depth to surface Abdul Sattar Othman Nani and zero-offset VSPs shot in 13 vertical wells. The QC- Ministry of Oil and Mineral Resources, Yemen VSP processing, based on semblance-weighted deconvolution, improves the originally low airgun source Oil and gas fields have been discovered in the Marib- frequency and makes the processed VSPs exceed 3-D Shabwa basin and oil seeps have been detected in the Tihama resolution. These VSPs consistently: (1) detect a powerful basin, both of which are associated with halokinesis in top Biyadh reflection which does not always tie the noise- different geological times. The salt in the Marib-Shabwa contaminated 3-D seismic; (2) confirm the weak or absent basin is Jurassic (Tithonian age) and an initial phase of top ShuÕaiba reflection; and (3) tie shallower strong halokinesis began in very Late Jurassic time. Features reflectors, such as the Rus and Aruma. associated with halokinesis were detected during seismic interpretation and include listric gaps, rollover structures, Tracking the Biyadh reflector on the 3-D is not turtle backs and salt pillows. All these structural features straightforward. The reflection pattern contains ambiguities are associated with listric faults, which played a positive which require interpretive separation between what is role for migrating hydrocarbon from Lam and Meem source geologically reasonable from what is not. The VSPs and rocks to the Alif reservoir rocks. synthetics demonstrate the presence of several strong multiples in the 3-D seismic which cause these ambiguities. The salt in the Tihama basin is Middle Miocene in age and A non-conventional approach whereby multiples identified an initial phase of halokinesis began in very Late Miocene by the VSP are tracked away from the wellbore clarifies time. Features associated with halokinesis were detected the geological section and leads to improved horizontal well during seismic interpretation and include salt-pillows, planning in the area around the vertical well. Nevertheless, stocks, detached stocks, tongues, canopies and salt cored in some cases, even careful multiple tracking fails to locate anticlines. A clear understanding of the implication of salt disruptions of the primary reflection, leading to erroneous tectonics in the Tihama basin will lead to oil and gas seismic picks. discoveries. Carefully edited and spliced sonic and density logs indicate Abdul Sattar Othman Nani received that sonic velocity increases while density decreases from his MSc and PhD degrees in the overlying shale to the porous ShuÕaiba reservoir. The Exploration from Baku University in resulting low acoustic impedance contrast yields a very 1978 and 1985, respectively. He weak ShuÕaiba reflector on the synthetics. Lack of valid completed his PhD Equivalency from density data in the often washed-out shale has been the University of Karachi in 1986. He responsible for the pseudo-ShuÕaiba reflector observed in has worked for the Ministry of Oil previous Shaybah synthetics. and Mineral Resources, Yemen since 1978. Abdul Sattar has published a The ShuÕaiba reservoir is characterized by fairly uniform number of scientific articles. porosity. However, in some areas, nuclear and sonic logs show a low-porosity interval with corresponding high

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acoustic impedance. The VSPs identify this potential flow baffle whose lateral extent can be delineated with the 3-D Utilization of Special and Conventional seismic. Core Analyses in Characterizing a Central Arabian Sandstone VSP surveys have also been deployed in a Òlook-aheadÓ mode whereby reflections from targets below the current total depth are detected. Extrapolation of the VSP first-arrival Taha M. Okasha, James J. Funk data is expected to yield more accurate depth estimates to and Yaslam S. Balobaid these horizons than existing velocity surveys at wells several Saudi Aramco tens of kilometers away. This paper describes the use of both special and conventional The VSPs at Shaybah have provided a very critical core analysis data in characterizing the Upper Permian calibration for the 3-D seismic data, confirming what is Central Arabian Sandstone. The test results of various special signal, isolating noise events which pose interpretation core analysis tests conducted over the years indicate that pitfalls, and improving time-to-depth conversion. With the core preservation and laboratory procedures play an re-processing of the Shaybah 3-D seismic data now in important role in defining relative permeability, capillary progress, the VSPs acquired to date will continue to serve pressure and wettability. as a valuable reference on seismic bandwidth, phase, amplitude, signal-to-noise ratio, and velocity. The results of conventional core analysis show high contrast in basic core properties (K and ¯). Large differences in Edgardo L. Nebrija received a PhD relationships between porosity and permeability support the in Geophysics from the University of complexity of the Central Arabian Sandstone. Porosity and Wisconsin at Madison. From 1979 to permeability variations from well to well, within the same 1992, he worked for Shell Offshore, area, and within the same formation, are significant. A new Inc. in New Orleans, Louisiana in technique has been developed to identify intervals with various capacities as Marine Seismic different porosity/permeability relationships. This technique Party Chief, Explorationist and presents reservoir quality index (RQI) as a function of depth Exploitation Geophysicist. Since and assists in describing reservoir units which have similar 1992, Ed has been a staff member of properties. the Northern Area Reservoir Geology Division of Saudi Aramco responsible for the seismic Relative permeability results of several wells using interpretation of the Shaybah 3-D seismic data in support composite cores at reservoir conditions indicated that oil of development drilling and reservoir characterization of recoveries ranged from 38% to 85% of original oil in place the Shu’aiba reservoir. He has also worked in the Marjan while residual oil saturations range from 16% to 27% of the field of offshore Arabian Gulf. Ed is a member of the SEG pore space. The results of modified Amott wettability tests and EAGE. and United States Bureau Measurements wettability indices revealed intermediate to water-wet character of the Central Bernard G. Frignet is Interpretation- Arabian sandstone reservoir with an increase in water-wet Development Geophysicist with characteristics with depth. Mercury injection tests showed Schlumberger-Middle East in Al- that this Upper Permian Sandstone reservoir can be classified Khobar, Saudi Arabia. He graduated as a trimodal pore system with different capillary character from Ecoles des Mines de Paris and and median pore radii varying from 0.1 to 4 microns. In in 1975 received a degree in addition, the cross-plotting of Amott indices to water and Amott indices to oil in a ternary diagram was introduced as Geophysics from Institut Français du a quick quantifying technique for wettability Pétrole. He started his career with characterization. Bureau de Recherches Geologiques et Mineres in Orleans, France and Taha M. Okasha is currently a joined Schlumberger in 1982. Bernard has held various Laboratory Scientist at Saudi Aramco Interpretation-Development assignments in the Africa- R&D Center in Dhahran, Saudi Mediterranean and the Far East regions before coming to Arabia. His major interests are the Middle East in 1990. His primary interest is the reservoir characterization, formation integration of seismic and wireline logs. He has contributed evaluation and enhanced oil several publications in the field of VSP and sonic. Bernard recovery. He holds BSc and MSc is a member of the SPE and SEG. degrees in Engineering Geology from Suez Canal University, Egypt and King Fahd University of Petroleum

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and Minerals (KFUPM), Saudi Arabia. Taha received his the purposes of wildcat exploration has allowed these PhD degree in Petroleum Engineering from KFUPM. He is stratigraphic concepts to be refined to a level of detail not a member of the SPE and ACS. previously possible. Also, sequence stratigraphic analysis and detailed biostratigraphy have played critical roles in James J. Funk is currently a Senior bringing these new prospects to maturity. Laboratory Scientist at Saudi Aramco R&D Center in Dhahran, Saudi Wendell G. Olivier is a Senior Arabia. His major interests are in Geologist with Chevron Overseas reservoir characterization, formation Petroleum (Qatar) Ltd. He received evaluation, NMR, and CT scanning his BSc in Geology from Nicholls applications. He holds a BA in State University in 1977 and MSc in Chemistry from the University of Geology from Idaho State University Houston and an MSc in Chemical in 1979. Wendell has worked for Engineering from the University of Gulf/Chevron for 18 years in a Florida. James was previously an Advanced Research variety of locations including the Gulf Engineer with Texaco Exploration and Technology of Mexico, Rocky Mountains, West Department in Houston, Texas. He has worked in several Coast of the US and Latin America. He is currently assigned areas of reservoir engineering including formation to the Africa/Middle East Business Unit working on the evaluation and core analysis. He is a member of SPE, Qatar project. SPWLA and SCA. Christopher W. Hollister is a Staff Yaslam S. Balobaid is currently a Geophysicist with Chevron Overseas Laboratory Scientist at Saudi Aramco Petroleum (Qatar) Ltd. He received R&D Center in Dhahran, Saudi his BSc degree in Applied Geophysics Arabia. He holds a BSc in Chemistry from the University of California, Los and Geology degree from United Arab Angeles in 1982, and his MSc degree Emirates University. Yaslam's areas of in Geophysics from Stanford interest are core analysis and reservoir University in 1987. Christopher characterization. He is a member of began his industry career with Gulf, the SPE. and joined Chevron in 1987. During his career, he has worked seismic interpretation projects in a variety of US domestic and overseas exploration areas.

New Stratigraphic Play Concepts in the Laszlo Varkonyi is currently the Cretaceous, Eastern Offshore Qatar Chief Geologist for the Middle East Region of the International Exploration and Production Division Wendell G. Olivier, Christopher W. Hollister of MOL (Hungarian Oil and Gas Chevron Overseas Petroleum (Qatar) Ltd. Company). Laszlo received his MSc Laszlo Varkonyi degree in Geology from the ELTE MOL Hungarian Oil & Gas Company University, Budapest, Hungary in and Rashid A. Al-Sulaiti 1985. In the first part of his career Qatar General Petroleum Corporation he worked on a variety of projects in Hungary. Since the early 1990s, Laszlo has been working Exploration activity in Qatar has traditionally focused on on foreign projects mainly in the Middle East, North Africa, Jurassic Arab Formation reservoirs, but recently operators and Southeast Asia. have been looking to the Cretaceous section as well for large untapped reserves. Recent production start-ups at Al- Rashid Ahmed Al-Sulaiti is the Shaheen field (Maersk-operated) and Al-Khalij field (Elf- Exploration Manager for Qatar operated) have indicated substantial potential for the General Petroleum Company Cretaceous reservoirs. These fields, and much of the (QGPC). Rashid received a BSc perceived remaining exploration prospectivity, involve degree in Petroleum Engineering stratigraphic traps. These stratigraphic play types range from Cairo University in 1977. He from the familiar platform-margin and salt-flank plays, to has been working on a variety of more exotic paleo-karst/diagenetic and hydrodynamic plays. assignments for QGPC for almost twenty years. In 1990, he assumed New exploration technologies have helped to generate new the position of Exploration Manager play concepts for the area. The advent of 3-D seismic for for QGPC.

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Basin Mechanics and the Predictability A Comprehensive Palynozonation of the of Fractured, Stylolitized and Vuggy Devonian-Carboniferous of the Gulf Region, Reservoir Location and Characteristics Middle East and North Africa

Peter J. Ortoleva Bernard Owens and Janet Lines Indiana University British Geological Survey/University of Sheffield

A three-dimensional model of basin stress and deformation Accurate palynostratigraphic calibration of the Devonian- history is used to predict the location and characteristics of Carboniferous sequences in the Gulf Region and throughout reservoirs. The inputs to the model are the present-day the Middle East are frequently impeded by the absence of a stratigraphic, thermal, and overall tectonic data from well regionally specific sequence of palynological biozones. logs, cores, surface geology, and seismic and other remote Correlations are commonly achieved by dependence on long techniques. The output is the evolution over the basin of range comparisons with assemblages from the Euramerican the generation of natural fractures, gouge, compaction, Continent. High reliance is commonly placed on the stylolites and vug stability. These predictions give, thereby, presence of a small number of stratigraphically significant the history of the creation of migration routes, seals and miospore taxa which are widely distributed throughout the reservoirs over the history of the evolving basin. Old Red Sandstone Continent and marine Devonian and the more varied facies regimes of the Carboniferous in northwest The model is applied to several basins to illustrate its use in Europe without any attempt to recognize the value of the petroleum exploration and production. The cases explored large number of indigenous taxa present in the northern are: (1) tight gas sand production from natural fractures margin of Gondwana. A major review of all published data (Piceance Basin, West Colorado, USA); (2) collapsed or available from Morocco to Iran has critically assessed all fractured vuggy reservoirs in carbonates with fracture- distribution data with particular emphasis on data sets from enhanced production (Permian Basin, West Texas, USA ); Saudi Arabia, Libya and Algeria. The large dataset generated and (3) salt tectonic-associated reservoirs (the US offshore permits the establishment of a comprehensive series of Gulf). These diverse examples can be analyzed with our twenty seven biozones extending from the Pridolian to the fully three-dimensional finite element model due to the Gzhelian. Independent biostratigraphical evidence to generality of our rock rheology. The latter integrates calibrate the zonal boundaries is sparse but all available poroelasticity, nonlinear continuous deformation, fracturing evidence is integrated. Correlations are proposed with all and pressure solution with diageneis, multi-phase hydrology previously established local basinal zonation schemes and and temperature dynamics. The result is a unique model local basinal lithostratigraphical units are assigned to the that yields important insights into the present-day and new zonal units. geological history of formations or whole basins of interest. Enhanced insights are gained because the interpretation of Bernard Owens is an Upper the usual data (seismic, well log, core analysis, etc.) are Paleozoic Palynologist working at constrained by the laws of fluid flow, diagenetic reaction the British Geological Survey in and rock mechanics. Nottingham where he is also Manager of the Basin Analysis and Peter J. Ortoleva has been analyzing Stratigraphy Group. During the past reaction-transport systems for the 18 years he has managed major last 28 years. During this period, he research projects involving a team of and his students have developed over leading European palynologists in 20 numerical codes for simulating Libya and the Arabian Peninsula. crystal growth, reaction-diffusion Bernard is a former President of the Commission systems, mechano-chemistry, reactive Internationale de Microflore du Paleozoique and currently flow in porous media, and stochastic holds an academic chair in the University of Sheffield where phenomena in reaction-transport he is Director of the Center for Palynological Studies. systems. The main emphasis of his work over the past 16 years has been on geochemical Janet Lines is a Technical Assistant phenomena in general and in the genesis and dynamics of in the Basin Analysis and compartments and the development of geochemical Stratigraphy Group of the British exploration and engineering codes. He has written two Geological Survey. In the last decade monographs on geochemistry and chemical reaction theory, she has been a contributor to major has edited an AAPG Memoir on compartments, and has review studies of the Carboniferous recently completed a monograph on basin palynology of the Arctic to North compartmentation. Africa and the Devonian- Carboniferous palynology of North Africa, Middle East and Gulf Region. 138

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Exploration in Compartmented Basins: The Seismic Sequence Stratigraphy Data Integration Through Diagenetic, of the Ghudun/Safiq Hydrologic, Mechanical Modeling (Ordovician and Silurian) of North Oman

Anthony J. Park Mark Partington, Tom Faulkner, Angus McCoss Indiana University and Eilard H. Hoogerduijn Starting Petroleum Development Oman Many reservoirs world-wide have been found in association with compartments, i.e., in sediments enclosed in The Ordovician and Silurian sediments of North Oman diagenetically enhanced permeability barriers. To further comprise a thick interval of proximal braid plain paralics the effort of exploration of these and to aide in their (Ghudun Formation) overlain by a series of shallow marine characterization, we have developed a three-dimensional mudstones and sandstones (Safiq Formation) probably numerical simulator, CIRF.B, that effectively uses observed deposited in a glacial/peri-glacial paleoenvironment. Over formation pressures, well logs, seismic data, and basin 33% of wells penetrating the interval have oil or gas shows. history and sediment composition data. In order to understand the hydrocarbon trapping potential of the Ghudun/Safiq in North Oman, a predictive sequence This program, CIRF.B, simulates diagenetic mineral stratigraphic framework was defined to constrain the lateral reactions and associated chemical compaction to capture and vertical distribution of reservoir, source and seal in the the development of seals and porosity and permeability area. modification. It simulates sediment deformation (including mechanical compaction) and stress evolution to predict the Based on detailed well log correlations and biostratigraphic location and history of fracturing, along with fluid flow. analysis of over 110 exploration wells, the Ordovician to Thus, the model simulates the formation of fractured and Silurian of North Oman is subdivided into five 2nd-order overpressured reservoirs, as well as the more classical tectono-stratigraphic units, within which over 20 shorter structural and stratigraphic traps. The model generates term, higher frequency changes are superimposed. The petroleum using thermal decomposition kinetics. depositional history of the Ghudun/Safiq was controlled by an interaction of eustatic sea-level variations, climate, To illustrate the applicability of the model, examples will sedimentation rates and local halokinetic subsidence, be shown from the Anadarko, Piceance, and West Texas resulting in a number of fining and coarsening upwards, Permian Basins of USA. These gas- and oil-rich basins 3rd-order, cycles of varying duration. A wide variety of provide a full suite of carbonate to siliciclastic reservoir vertical and lateral facies changes are recognized within the lithologies where production is from matrix, vug, karst, or Safiq Group of North Oman, from proximal braid plain fractures. Of particular interest here is the Permian Basin, sandstones and shelf sands, to deeper water mass flows. West Texas, which has many facets in common with the producing carbonate fields of the Middle East. Comparisons The recognition and identification of regionally correlatable of predicted and observed compartments from this region units within the Ordovician and Silurian sequences of North will be presented. Oman has resulted in the identification of three major play opportunities with a wide variety of minor play Anthony J. Park completed the opportunities. Bachelor of Science degree in Geology from the University of The exploration well-based scheme was further integrated Washington, in 1985. Since then he and tested with the observed seismic sequence stratigraphy has been associated with the to produce a predictive template which is currently being Department of Geology at Indiana tested by a vigorous exploration campaign. One of these University, where he has completed plays has already been positively tested and is currently the Master of Science and Doctor of under appraisal. Philosophy degrees in Theoretical Geochemistry. He is currently a Mark Partington is currently a Senior Research Associate at the Laboratory for Computational Seismic Interpreter in Petroleum Geodynamics. While working for the graduate degrees, Development Oman (PDO). He has Anthony has done extensive internship and contract work MSc and PhD degrees from University for Amoco and Mobil. For two years, from 1995 to 1996, College, London and the University of he was a post-doctoral fellow at the Institut Français du Aberdeen. Mark has 17 years Pétrole in Rueil-Malmaison, France. petroleum exploration experience. Before joining PDO he was employed as a Consultant Stratigrapher by Shell

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International in the Netherlands, prior to which he worked as In the study area, the sparsely spaced and shallow uphole an Exploration Geologist and Palynologist with BP and control points could not be used to generate a reliable 3-D Robertson Research International, working mainly on the UK average velocity-depth model. The base of weathering is and Norwegian North Sea. Mark has published over 10 papers well below the maximum uphole penetration depth. on exploration geology, stratigraphy and palaeontology. Fortunately, the spatially-varying unconsolidated sand are underlain by multiple refractors. The first breaks can be Tom Faulkner (see abstract "The Athel Play in Oman: reliably picked and a delay time solution calculated. But Controls on Reservoir Quality" on page 61 for biography without accurate velocity or depth of weathering control, a and photograph) velocity-depth ambiguity problem exists and a unique refraction static solution cannot be obtained from accurate Angus McCoss is New Opportunities time delays. This ambiguity can be overcome only by Team Leader in the Exploration drilling strategically placed upholes through the base of Department at Petroleum weathering or indirect velocity measurements from shallow Development Oman (PDO). Angus reflectors. Otherwise, we rely on the creative interpretation has a PhD in Structural Geology from skill of the interpreter and the near-surface modeler. The Queens University, Belfast. Before interpreted near-surface velocity-depth model is used to joining PDO, Angus worked for New calculate datum statics and applied to the stacked time Opportunities in Shell China and section which effectively downward continues the sources Shell Research in The Netherlands. and receivers to a seismic reference datum (SRD). At this stage, the interpreter typically assumes the datum- corrected time section is free of most near-surface velocity anomalies. Eilard H. Hoogerduijn Starting received a PhD in Structural Geology Prospect generation begins by identifying time anomalies, from Utrecht University in 1991. He interpreting time horizons and converting these time joined Shell in the same year and was horizons to depth horizons. The process of converting a posted to SIPM (later SIEP) in The time section to depth section ultimately determines if these Hague, Netherlands. There Eilard time anomalies have any commercial value. There are was involved in the development of several top-down approaches available for converting a time prospect evaluation software. section to a depth section and all depend on the initial near- Subsequently he moved into a new surface velocity-depth model. If the top macro layer(s) are venture exploration team, looking at not accurately modeled and validated, these errors will opportunities in the Middle East. Following a year in a propagate into the subsurface and introduce or remove reorganization team, he got involved with fault-seal analysis structures. research in Shell's EP Research organization in Rijswijk, Netherlands. Eilard joined Petroleum Development Oman's A strike and dip line (over an existing low-relief field) were Frontier Exploration Team in mid-1997. chosen which cover an area with nearly flat surface topography and formations dipping at angles of less than one degree. Independent near-surface velocity-depth models Resolving the Near-Surface were constructed and compared from upholes, refraction Velocity-Depth Ambiguity delay time solutions and coherency inversion. Each of these independent shallow structures differently affect the conversion of time-to-depth. The shallow reflection data Peter I. Pecholcs, Son Nguyen was carefully reprocessed, interpreted and integrated with Saudi Aramco constrained reflection/refraction tomography and pre-stack and Dan Kosloff depth migration methods to improve the accuracy of the Paradigm Geophysical depth image. Final time-to-depth conversion velocities were calibrated with sonic logs and check shot surveys. In Central Saudi Arabia, seismic data is acquired along lines over near-surface conditions which include different Peter I. Pecholcs is currently combinations of sand lenses, buried channels, shallow working with Saudi Aramco. He leaching, subcropping formations, and in some areas the received a BSc degree from Suny effects of a shallow unconfined aquifer. In addition, recent StonyBrook in 1980 and a MSc field work has shown the existence of significant post- degree from Columbia University in Triassic surface folds which may have formed by anhydrite 1982. Prior to joining Saudi Aramco, dissolution and collapse or basement reactivation. These Peter worked with Sohio Petroleum variable near-surface conditions give rise to both lateral between 1983 and 1988, the velocity and structural variations and thus to time anomalies University of Hawaii between 1988 with wavelengths as small as a common depth point interval and 1991 and United States and much greater than an effective spread length.

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Geological Survey from 1991 to 1992. He is interested in A regional unconformity is present at the base of the Aptian- wave propagation and inversion. Cenomanian Mardin Group which is the main oil-producing sequence in Southeast Turkey. This group is represented Son Nguyen is currently working by various types of shallow marine carbonates and semi- with Saudi Aramco. Son received his restricted deep marine organic-rich carbonates. After a BSc degree from MSU in 1980. He sedimentological break, transgressive shallow to deep worked with Teknica Inc. between marine deposits were developed during the Coniacian and 1982 and 1988, Interseis Inc. between Maastrichtian. The presence of the Upper Campanian- 1988 and 1989 and Geocenter Inc. Lower Maastrichtian turbiditic clastics is an indicator of the between 1989 and 1990. Son is intense tectonism in the northern part of Southeast Turkey. interested in seismic data processing Following this tectonic phase, reefoidal and bank-type and inversion. carbonates were deposited in relatively stable, marginal and platform-type marine environments in the north. However, Dan Kosloff holds a PhD degree from the California the southern parts were the area of deep-marine deposition. Institute of Technology in 1978. Since 1992 Dan has been These conditions prevailed at the end of the Paleocene. working with Paradigm Geophysical. He is interested in During the Early-Middle Eocene an extensional tectonic seismic wave propagation and inversion. regime was effective in the north. The Early-Middle Eocene deposition was terminated by a regression in the Late Oligocene time. Paleogeographic Evolution of the Northern Arabian Plate After a regional hiatus, the sedimentation in a transgressive sea took place during the Early-Middle Miocene. Turbiditic clastics, bank-type carbonates and shallow marine to Dogan Perincek continental clastics and carbonates were deposited during King Fahd University of Petroleum & Minerals this time. The deposition ended with the alluvial and fluvial Orhan Duran, Nihat Bozdogan and Tanyol Coruh deposits of the Late Miocene to Pliocene. Turkish Petroleum Corporation Dogan Perincek received his MSc in Southeast Turkey is located at the northern margin of the Geology and PhD in Petroleum Arabian Plate. Sedimentary rocks were deposited in several Geology from the University of basins from Precambrian to Recent. The autochthonous Istanbul in 1972 and 1978, strata were effected by tectonic events which caused several respectively. He worked with the sedimentological breaks and unconformities. Turkish Petroleum Corporation as a Structural Geologist and Petroleum The oldest known lithostratigraphic unit is the Precambrian Explorationist between 1975 and volcanoclastic, shale and sandstone. It is overlain 1989. Dogan also worked with King unconformably by the Cambrian, which is characterized by Fahd University of Petroleum and continental to transitional type clastics at the bottom, shelf Minerals (KFUPM) as Research Scientist, as an carbonates in the middle, and shallow marine shale and Explorationist with Mobil Exploration and Huffco Turkey sandstone alternations at the top. This unit grades into Incorporated, as Geophysicist with the Geological Survey coastal shallow marine deposits of the Ordovician sequence of Victoria (1992), Geological Survey of Western Australia which is overlain by the Upper Devonian-Lower (1995) and World Geoscience Co. Ltd. (1997). Dogan Carboniferous coastal to shallow marine deposits in the east. rejoined KFUPM in late 1997. Dogan is a member of the Above a regional unconformity, the Upper Silurian-Middle AAPG, Australian Society of Exploration Geophysicists, Devonian shallow marine rocks were deposited in the central Petroleum Exploration Society of Australia and Dhahran part of Southeast Turkey. The Permian, composed mostly Geological Society. of carbonates and some clastics, is present only in the eastern part of the study area. Orhan Duran received his MSc degree from the University of Istanbul The Paleozoic and Mesozoic rocks seem to be comformable and joined Turkish Petroleum with minor breaks in sedimentation in the eastern part of Corporation (TPAO) in 1974. He Southeast Turkey. The Lower Triassic comprises two worked with the Arabian Gulf Oil argillaceous carbonate units separated by a red bed sequence. Company in Benghazi, Libya between The overlying Middle Triassic-Lower Cretaceous sequence 1982 and 1986. He returned to TPAO is represented by a carbonate-evaporate sequence of as a Senior Geologist and then restricted to open marine environments in the mid-southern became a Deputy Group Manager of parts. It grades laterally into shallow marine carbonates, International Projects. He is both in the eastward and westward directions.

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currently Group Manager of the Research Center. Orhan using the uphole model exhibited false time structures of published numerous papers and is a member of the AAPG, ±12 meters resulting from near-surface velocity variations. Chamber of Geological Engineers of Turkey, Association The very gentle real structure of Nuayyim field necessitated of Petroleum Geologists of Turkey and EAGE. a better datum solution. A water-table datum was found to be considerably more effective than the uphole solution in Nihat Bozdogan received a MSc removing near-surface velocity effects. degree in Geology from Hacettepe University in Ankara, Turkey. He William M. Petersen (see abstract "Geochemical Evidence joined the Research Center of the for Reservoir Compartmentalization in Central Arabian Turkish Petroleum Corporation as a Paleozoic Reservoirs" on page 96 for biography and Stratigrapher. Nihat is currently photograph) Manager of the Stratigraphy Department of the Research Center. Marty Rademakers (see abstract "Improved His interests include palyno- Characterization of the Unayzah Reservoir, Central Arabia, stratigraphy, palinofacies, petroleum from 3-D Seismic with Stratigraphic Inversion and Statistical system and paleogeographic evaluation of Paleozoic Pattern Recognition" on page 124 for biography and sequence of southeastern Turkey and the Arabian Plate. photograph)

Tanyol Coruh received his MSc degree in Geology from Hacettepe Layered Acoustic Impedance Inversion and University in Ankara, Turkey in 1973. He worked for the Mineral Research its Impact on Reservoir Characterization and Exploration Institute of Turkey as a Field Geologist for four years. Stephen J. Pharez, Andrew Strachan and Jo White In 1977 he joined the Research Compagnie Générale de Géophysique Center of the Turkish Petroleum Corporation as a Stratigrapher. His From reduction of exploration risk, through to optimizing main interest is foraminifera field management, reservoir characterization is a common biostratigraphy of southeastern Turkey. problem throughout the exploration and production cycle, and seismic data have a key role in the reservoir characterization process. Gluck et al. (1996) described a unique, layered approach to acoustic impedance inversion Seismic Imaging of a Water Table and and here we demonstrate the use of the technique in its Use as a 3-D Seismic Datum identifying the spatial extent and quality of reservoir sands from two differing environments; the North Sea and offshore William M. Petersen and Marty Rademakers Nigeria. Saudi Aramco The acoustic impedance inversion technique used, employs A distinctive shallow seismic event is noted on seismic a model-based approach to produce a finely- stratified, records acquired in a portion of Central Arabia, east and broad-band impedance model. This model is iteratively south of Riyadh. This event is relatively flat, and is cut by updated with impedance and interface variations on a global reflections that abruptly change seismic character as they basis. One of the benefits of this truly 3-D technique is that cross the event. Analysis of well-log data and synthetic the starting macro-model requires only sparse a priori seismograms indicate that the event is the seismic response knowledge and does not require direct input of the well logs to the local water table, which, in the area of this study, is at in any form. This means that all available wells can be used a depth of about 1,000 feet. The water-table seismic event to validate the final layered impedance micro-model and is developed within the porous sands of the Biyadh thus enable lateral prediction of lithology, porosity and fluid Formation, but terminates to the west where the water table content within a reservoir. enters the Buwaib carbonates. To the east, north and south, the event extends beyond the study area. 3-D time horizons located at the main impedance breaks define the initial macro model layers. From this, a series of The water-table seismic event proved to be of use in finely-stratified layers, are produced by optimizing the match providing an acceptable datum-statics solution for the between the observed and modeled seismic data using a Nuayyim field 3-D seismic survey. The initial datum-statics simulated annealing method. This may then be output as a model for the survey was derived from a grid of 143 upholes, conventional cube and examined using an interpretation drilled 200 to 600 feet deep. The 3-D seismic data processed workstation. However, as each layer has time, impedance and thickness attributes, a higher level of information content

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can be extracted by visualizing these layers in 3-D; not only Andrew Strachan has more than to reveal the local variation of impedance within a layer, three and a half years industry but also to examine the connectivity between reservoir experience, three of which are with segments. Compagnie Générale de Géophysique (CGG), after completing an MSc in During the inversion of a migrated volume from the North Exploration Geophysics from Sea, a number of significant features were identified. We Imperial College, London. will illustrate the presence of a low impedance structure Throughout his time at CGG he has with channel morphology which is not visible on the seismic been involved in a variety of projects amplitude data due to tuning effects. At the target level, a ranging from depth imaging, acoustic high impedance zone was also resolved between two wells. impedance inversion studies and OBC multi-component This indicated the possibility of a permeability barrier within processing. the reservoir and the correlation with well data will be explored. Jo White joined Compagnie Générale de Géophysique's Our second study is a relatively simple roll- Integrated Geoscience Services over structure of alternating deltaic sand-shale sequence with Department as a Geologist, having dip closure. The principle reservoir sands are variable in gained 3 years experience working quality but show a clear low impedance response, which is in the UK for two US oil companies enhanced by the presence of oil. Calibration to well data (Conoco and Brabant). His expertise shows there is excellent delineation of the producing is in 3-D seismic interpretation, depth reservoirs from the seismic impedance response. Inversion mapping and well log analysis. He of the seismic data correlates with the known porosity received his MSc degree in Petroleum information and delineates the extent of the reservoir; in Geology from Imperial College and MA in Geology from particular, the shaling-out of the deeper sand downdip. The the University of Cambridge. Jo is a member of the AAPG results also show the presence of a thin shale cap on the and PESGB. main reservoir sand which is not visible on the seismic but is highlighted by the inversion. The Structural and Tectonic Evolution of The use of a unique, layered approach to acoustic impedance inversion, combined with visualization of the resultant layer East-Central Oman from the attributes, provides a very powerful tool for reservoir Cambrian to the Tertiary characterization studies and the planning of horizontal well trajectories. The layer geometries, which are derived without Robin Pilcher, Amerada Hess Ltd., UK, interpretation, conform to known lithostratigraphic Gerald P. Roberts and Neil A. Harbury boundaries and greatly aid the identification of features not Birkbeck College and University College London resolved on the original seismic data. Calibration of the impedance volume with petrophysical data permits The Huqf Uplift is a long-lived structural high situated in delineation of the main reservoir sands, which coupled with east-central Oman, on the southeast margin of the Arabian volumetric visualization enables connectivity evaluation. Plate. Structural mapping was carried out in this area between 1993 and 1996 to determine the geometries, Stephen J. Pharez received a BSc kinematics and timing of deformation in the Huqf Uplift. degree (Honors) in Geophysical The results of a detailed field based study in the region, Sciences from Southampton presented here, are used to constrain the structural and University and has since spent 20 tectonic evolution of east-central Oman. Evidence for two years within the industry in both distinct structural deformation phases between the service and oil company sectors. Precambrian-Cambrian and Tertiary is presented: a Most recently Stephen was with the Precambrian-Cambrian phase of east-west extension and a BP/Statoil alliance before joining late-Cretaceous phase of north-south left-lateral strike-slip. Compagnie Générale de For each of these deformation phases structures, such as Géophysique 2 years ago to head the strike-slip faults, folds, thrusts, normal faults, joints, were Integrated Geoscience activity in London. Areas of interest recorded in the field and used to determine the geometry include depth imaging, multiple suppression and the use of and kinematics of deformation. The timing of deformation seismic attributes for reservoir characterization. is constrained using a combination of published stratigraphic schemes, primary field logging, sample collection and nannofossil dating.

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In the Huqf Uplift, the Precambrian-Cambrian extensional Shell Research in the Netherlands. The survey was carried event is characterised by north-south trending normal faults out in 1991-1992 and comprised the acquisition, processing with erosionally truncated footwall topography, and fanning and interpretation of a 28.4 square kilometer 3-D nine- fluvial paleocurrent patterns. Published models for the component survey over the Natih field in Northern Oman. tectonic driving forces responsible for this deformation do After an introduction to the geological, geophysical and not satisfactorily explain the structures recorded during this reservoir engineering aspects we present maps of the study and a new model is proposed whereby the extensional polarization and time splitting between the fast and the slow basins in Oman formed in response to left-lateral motions shear wave over the Natih reservoir. The observed very large on the Najd Fault Zone. The strike-slip deformation is anisotropy, viz. in excess of 20 percent time splitting over a characterised by major north-south, left-lateral large part of the survey, suggests that the main objective of transpressional strike-slip faults and associated folds and the experiment -fracture detection by a multi-component 3- Riedel shear arrays. Outcrops of ophiolitic strata along the D survey - has been met. An independent fault modelling southeastern margin of Oman were also examined and found exercise was undertaken on the Natih field based on the to contain similar left-lateral transpressive structures. A new complete 3-D seismic survey results. Fault/fracture tectonic model for the relationship between the plate-margin ‘domains’ were identified on the basis of fault frequency processes responsible for ophiolite obduction, and the strike- and orientation. Comparisons with the 9C3D results showed slip structures in eastern Oman, is proposed. that the domains were present in the latter data set as areas of coherent splitting character. A review of the production Robin Pilcher received his MSc in data for the field indicated that the domains were consistent Applied Structural Geology and Rock with well behavior reflecting the degree of fracturing. Mechanics from the Royal School of Mines, Imperial College, London in In addition, we present evidence that shear waves are 1993. He gained his PhD, a study of sensitive to fluid type in fractured media. Two observations the structural and tectonic evolution are examined from the Natih 9C3D data where regions of of the Huqf uplift, Oman, from gas are characterised by slow shear velocities. Firstly, the Birkbeck College, University of shear-wave splitting map of the Natih reservoir exhibits London in 1997. Robin currently much larger splitting values over the gas cap on the reservoir. works as an Exploration Geologist It is argued that this increase in splitting results from a with Amerada Hess Ltd., UK. decrease in the slow shear velocity which is a response to both fractures and the fracture filling fluid. Secondly, the Gerald P. Roberts achieved his BSc thick Fiqa shale overburden exhibits a low shear-velocity in Geology in 1987 from the anomaly that is accompanied by higher shear reflectivity University of Wales, his PhD in and lower frequency content. No such effects are evident in Structural Geology from the the conventional P-wave data. This feature is interpreted as University of Durham in 1991, and a response to a gas chimney above the reservoir, a conclusion then became a Natural Environment supported by both effective-medium modelling, drilling data Research Council Research Fellow at and geological knowledge. the University of Manchester in 1990 to 1992. Gerald was appointed as a The introduction of gas in fractured rock appears to decrease Lecturer in Structural Geology and the shear velocity whilst leaving the compressional velocity Tectonics at the University of London in 1992. largely unaffected. This conclusion has direct implications for seismic methods in exploration, appraisal and Neil A. Harbury (see abstract "A Regional Sedimentological development of fractured reservoirs and suggests that S- Study of the Lower Cretaceous Shu'aiba Formation in wave data, rather than the conventional P-wave data, provide Oman" on page 53 for biography and photograph) direct hydrocarbon indicators. These observations are supported with modelling results.

Latest Results of the Natih 9C3D Hans Potters obtained a PhD in Seismic Survey Physics at Utrecht University in 1984. He worked on velocity modeling, inversion, AVO, rock Hans Potters and Vic Hitchings properties and shear seismic during Petroleum Development Oman research and section head assignments with Shell in the In this paper we discuss the latest results of the Natih 9- Netherlands and the USA. Hans component 3-dimensional (9C3D) seismic reservoir became head of the Quantitative characterisation experiment carried out jointly by Petroleum Interpretation and Geophysical Development Oman, the main oil producer in Oman, and Support group in Petroleum Development Oman in 1994. 144

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Vic Hitchings obtained a PhD in visualizing and analyzing complex three-dimensional Geology at University College, geological data. Hussam also has a special interest in Swansea in 1982. He worked in core graphics and operating systems. evaluation with Robertson Research for six years in the U.K. and Peter J. Ortoleva (see abstract "Basin Mechanics and the Southeast Asia and joined Shell in Predictability of Fractured, Stylolitized and Vuggy Reservoir 1986 as a Reservoir Geologist Location and Characteristics" on page 138 for biography working in The Netherlands and and photograph) Nigeria. In 1993 Vic joined Petroleum Development Oman and has worked as the Senior Production Geologist with Fahud/ Cambrian Intra-Salt Carbonate Natih/Lekhwair area developing static reservoir models of faulted and fractured reservoirs. Stringers of South Oman: Reviving a Complex Exploration Play

Fault and Flexure Analysis Joachim W. Reinhardt, Folco Hoogendijk, Ruwaina Al-Riyami, Joachim E. Amthor, Using Formation Top Data Glen Williams and Neil L. Frewin Petroleum Development Oman Hussam Qasem and Peter J. Ortoleva Indiana University In the period 1978-1983 Petroleum Development Oman (PDO) drilled a number of oil and gas discoveries on Data on formation tops is used to identify faults and flexure carbonate stringer objectives in the Southern Oman Salt and characterize them quantitatively. A statistical analysis Basin. The stringer reservoirs consist of porous dolomites, allows for the estimation of uncertainties inherent in the often over-pressured and stratigraphically trapped in the input data. The result of our data analysis package is a three- Cambrian Ara Salt Formation. Although potentially dimensional characterization of faults and flexure, a related rewarding, with well flow rates up to 1,400 m3 of oil per discretization grid adapted to these features for reservoir day, the play was found to be complex with respect to simulation, and graphical tools for viewing these structures. reservoir quality prediction, production behavior, Matrix yield criteria and vug and karst collapse criteria are hydrocarbon charge and seismic imaging. As a result, despite included to estimate the stability of fracture and a large number of identified prospects, the play has received macroporosity and related producibility. relatively little and only sporadic attention in the past years.

The analysis is applied to the Permian Basin, West Texas, An integrated project team, established in late 1996 within U.S.A., which has carbonate reservoirs of varying the Exploration Unit of PDO, is aiming at fully assessing depositional environments. Of interest for this presentation the remaining upside potential of the play by applying new are the basin’s characteristics which are similar to those of seismic and geological concepts and drilling structures the Middle East carbonate strata. Correlations of similarities representative of the prospect portfolio. Increasingly between these two environments may demonstrate the available 3-D seismic data and its integration with usability of the proposed analysis for Middle East petroleum sedimentological, geochemical and structural data, is resources. essential for the improved understanding of the play.

Hussam Qasem graduated from A critical success factor for the play is the 3-D seismic Shaikh Abdul-Aziz Secondary High imaging of the stringer prospects. Long-offset recording School in Manama, Bahrain. He has during the seismic acquisition stage has proven to be crucial. attended Indiana University since During data processing, the removal of seismic multiples, January 1995 and is pursuing a imaging of steeply dipping events such as the flanks of the degree in Computer Science. He was salt and the carbonate stringers themselves, and careful an Associate Instructor in the velocity picking have significantly improved the 3-D Computer Science Department at seismic data quality. During the interpretation stage, seismic- Indiana University from January to-well matching, seismic attribute mapping, careful 1996 until May 1997. In October selection of display parameters, and the application of an 1996, Hussam joined a biochemistry group in the Chemistry inverse “bottom-to-top” seismic stratigraphic correlation Department of Indiana University as a Computer System method are important. Administrator and subsequently joined the Laboratory for Computational Geodynamics in March 1997 as a System Analyst. Currently, Hussam is developing techniques for

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As a first step of the project, a new intra-salt stratigraphic Joachim E. Amthor (see abstract "Sedimentology, framework based on seismic stratigraphy, a reinterpretation Diagenesis and Charge History of the Haima Deep Gas of well log and core data using the concept of evaporite- Reservoirs in North Oman: An Integrated Approach to Play carbonate sequences, and chemostratigraphy was Evaluation" on page 60 for biography and photograph) established. This data, merged with regional 3-D seismic structural maps, aided in constructing a series of Glen Williams is currently working paleogeographic maps showing predicted reservoir trends as a Geophysicist in the Quantitative in space and time. In addition, focused geochemical studies Seismic Inter-pretation Team in the have addressed the issues of source rock distribution, Exploration Unit of Petroleum maturity and richness. Development Oman (PDO). He joined PDO as a Contractor from the The stringer prospects have now been grouped into risk Geocon Group in early 1997, and has classes using a seismic facies classification scheme, a some twenty years of experience as reservoir facies prediction model, the hydrocarbon charge an Exploration Geophysicist, mostly risk and finally operational requirements, i.e. type of rig in the Western Canadian Basin. based on the prospect depths and pressure regime. Prior to his assignment with PDO, he worked in Libya with Veba Oil. Glen holds a BSc with Honors in Physics from Joachim W. Reinhardt is currently the University of Victoria, Canada. working as a Senior Seismic Interpreter in the South Oman Neil L. Frewin (see abstract "Oil Families of Oman" on Frontier Exploration Team of page 55 for biography and photograph) Petroleum Development Oman (PDO). He has been Project Coordinator of the Intra-salt Integrated Haushi Hydrocarbon Habitat Carbonate Stringer Theme since his arrival at PDO in late 1996. Joachim Study in North Oman holds a MSc with Honors in Geology from Erlangen University in Germany. He joined Shell Pascal D. Richard, Peter J.R. Nederlof, International in 1988 and has since worked for NAM in The Jos J.M. Terken and Nashwa Al-Ruwehy Netherlands, Myanma Shell in Rangoon/Burma and Shell Petroleum Development Oman China in Beijing. In North Oman 20 fields, with a combined STOIIP of 500 Folco Hoogendijk is a Seismic million m3, have reserves booked in the Haushi (Gharif and Interpreter working for Petroleum Al Khlata) reservoirs. In addition, some 150 prospects are Development Oman (PDO) in the recognized with a combined UR expectation of 39 million South Oman Frontier Exploration m3. Following a successful exploration campaign, the Team’s Intra-salt Carbonate Stringer success ratio decreased progressively. An integrated charge project. He holds a MSc in Geology and retention study was therefore carried out to revitalize from Utrecht University in The the play. The aim of the study was to establish a framework Netherlands and joined Shell for predicting fluid content (gas, oil, water). Components International in 1989. Folco joined of this were a charge study to explain the hydrocarbon PDO in 1996 after working for Shell distribution on a basin scale, and a retention study addressing Expro in London for 6 years. top and fault seal quality.

Ruwaina Al-Riyami is currently The oil in the Haushi has been generated by three different working as a Seismic Interpreter in source rocks: Q, Huqf (Shuram) and Safiq. However, oil the South Oman Frontier Exploration typing shows that over 90% of the oil in place is derived Team of Petroleum Development from the 'Q' source rock. This seems to indicate a charge Oman (PDO). She joined PDO in problem for prospects outside the 'Q' migration fairways. 1994 after obtaining an MSc in The 'Q' kitchen was defined with the help of chemical Geology from San Diego State odometers, nitrogen compounds whose relative University. Ruwaina has been concentrations provide a measure of migration distance. involved in the Intra-salt Carbonate Measurements on 18 'Q' oils suggest a source area on the Stringer Theme project since late western margin of the Ghaba Salt basin, immediately to the 1996. east of Ramlat Rawl and Saih Rawl. Seismic lines across this area show salt filled rim synclines which possibly contain the 'Q' source beds.

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The two main sealing lithologies are carbonate (Khuff and Sequence Stratigraphy of the Haushi Limestone) and shale (intra Haushi shales), which can act as both top seal and/or fault seal. Based on log Post-Nappe Units of Oman response, seal lithologies for gas-only, gas-and-oil and oil- (Maastrichtian to Miocene) only could not be discriminated. Recent mud logs over the Khuff Formation (top seal of the Gharif reservoirs) showed Jack Roger, Philippe Razin, Chantal Bourdillon no evidence for a gas fraction, suggesting that the Khuff is and Robert Wyns an efficient gas seal. However, it has been observed that gas Bureau de Recherches Géologiques et Minières fields tends to have thicker Khuff seals and smaller fault throw than the oil fields. This trend is related to the regional Detailed sedimentologic and biostratigraphic analysis of the westward tilting of the basin during Khuff deposition. Maastrichtian to Miocene post-nappe units of the Oman Mountains has made it possible to establish a more complete Fault seal has been analyzed on across-fault juxtaposition regional sequence stratigraphy chart. Maastrichtian to diagrams. Highly faulted prospects above salt domes are Miocene deformation of the Oman Mountains, in part water bearing. However, apart from these extreme cases, inherited from Late Cretaceous Alpine structures, led to a seal breaching is not seen as a general problem. Sand-sand new paleogeographic configuration with development of the juxtaposition areas along faults were calculated in several Buraymi Basin in the northwest of the mountain belt and Gharif accumulations. Although cross fault juxtaposition the Abat Basin in the southeast. These two areas show was identified as the critical factor determining the platform-basin transition with a more complete stratigraphic hydrocarbon contacts in some moderately faulted fields (e.g. sequence than in the Arabian Platform. Burhaan), there seems to be no general relation between fault throw and hydrocarbon retention . Eleven, 2nd-order depositional sequences have been identified, corresponding to major transgressive-regressive Based on the long-distance migration of the Q oil proven cycles, and show a depositional partitioning between by the chemical odometers, and the relation between platform and basin that can be directly related to tectonic hydrocarbon fill and Khuff thickness, an opportunity map activity. The periods of tectonic relaxation, reflected by has been generated for North Oman. A strategy of exploring subsidence, are characterized by aggradation of the for stratigraphic traps in the Q migration fairways is deemed carbonate shelves onlapping the Arabian craton, i.e. to have the greatest chance of success. Maastrichtian, Selandian-Thanetian, Ilerdian-Ypresian, Lutetian, Bartonian, Priabonian, Rupelian, Chattian- Pascal D. Richard is a Structural Aquitanian, Burdigalian-Langhian. The periods of Geologist with Shell Exploration extensional tectonism are marked by craton uplift and since 1991. Pascal received his PhD emergence, with slope and hemipelagic deposition being from Rennes University, France, in restricted to the reactivated basins and faulted margins of 1989. He spent five years at the the former platforms, i.e. latest Maastrichtian-Danian, research lab KSEPL in the structural Cuisian, latest Bartonian-Early Priabonian, latest Rupelian. geology group where he was involved The Early Miocene compressional tectonism caused infilling in hydrocarbon migration studies and of the last active troughs and uplift of the present Oman was responsible for Structural Mountain chain. Sandbox Modeling. Pascal is now the Structural Geology focal point in the Exploration Unit of Jack Roger and Philippe Razin (see abstract Petroleum Development Oman. He is particularly interested "Sedimentology and Reservoir Geometry of the Late in Strike-slip Tectonics, Sandbox Modeling and Prospect Permian Upper Gharif and Lower Khuff Formations in Evaluation. Interior Oman: Outcrop Study in the Haushi Area" on pages 82-83 for biographies and photographs) Peter J.R. Nederlof (see abstract "Distribution and Formation of Pyrobitumen in Haima Reservoirs in North Chantal Bourdillon has been with Oman" on pages 101-102 for biography and photograph) the Bureau de Recherches Géologiques et Minières since 1982. Jos J.M. Terken (see abstract "Sedimentology, Diagenesis She received a PhD degree from the and Charge History of the Haima Deep Gas Reservoirs in University of Marseille. She has been North Oman: An Integrated Approach to Play Evaluation" involved in biostrati-graphical on page 60 for biography and photograph) studies of Oman, Saudi Arabia and Red Sea. Chantal is interested in Nashwa Al-Ruwehy (see abstract "Oil Families of Oman" Maastrichtian to Priabonian on page 55 for biography and photograph) biological events. She is a member

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of the French Geological Society, of the European S. Duffy Russell is currently a Senior Paleontological Society, the French Paleontological Review Geologist with the Abu Dhabi Association and the Group of Paleogene Study. Company for Onshore Oil Operations (ADCO). After receiving Robert Wyns (see abstract "The Paleozoic Succession of his BSc degree in Geology from North the Tabuk Basin in Saudi Arabia: Lithostratigraphy, Carolina State University and MSc Sedimentology and Sequence Stratigraphy" on page 105 for in Geology from Duke University, he biography and photograph) spent over 18 years as a Geologist in various Exploration and Producing assignments with Mobil Oil Meteoric Diagenesis and Porosity Evolution Corporation and as a Geophysicist at Amoco Production Company. His current studies in carbonate diagenesis and Using Cathodoluminescence Petrography, sedimentology are part of an ongoing PhD research project Shu'aiba Formation (Lower Cretaceous), at the University of Aberdeen. He is a member of the AAPG, Abu Dhabi, United Arab Emirates SEPM, SEE, and SPE. and Jebel Akhdar, Oman Gordon M. Walkden is currently the S. Duffy Russell Head of the Department of Geology Abu Dhabi Company for Onshore Oil Operations and Petroleum Geology at the and Gordon M. Walkden University of Aberdeen, Scotland. University of Aberdeen After receiving a degree from Quintin School in London, he obtained his Previous workers have successfully determined porosity PhD in Carbonate Sedimentology evolution using cathodoluminescence (CL) petrography on from Manchester University in 1970 sediments of different ages and geographic locations, yet . Gordon was appointed Lecturer in little CL data is available for the Shu'aiba Formation. The the Department of Geology and Shu'aiba provides one of the best examples of CL response Petroleum Geology and Senior Lecturer in 1988, and in carbonate sediments from four subsurface and six outcrop became Department Head in 1993. He has extensive field study areas. Petrographic studies of porosity evolution experience and supervision of research in Britain, Europe, through the application of CL analysis reveal a complex North America and the Middle East. diagenetic history of exposure to mixed meteoric and marine pore fluids. Although there is no conclusive evidence of subaerial exposure (such as caliche, paleokarsts, vadose Attribute-Driven Porosity Estimation cements), there is direct evidence of significant exposure to by Neural Systems meteoric pore fluids within a phreatic environment. Muhammad M. Saggaf and Husam Al-Mustafa The diagenesis of the Shu'aiba involved early marine and Saudi Aramco meteoric cementation phases and late meteoric-marine mixed cementation. Early syntaxial cements reveal a Neural networks are dynamic systems composed of a large sequence of four clear zonations - non-luminescent (NL), number of interconnected cells, or neurons. In the brain an bright, dull, and bright/dull subzoned cements. Microprobe enormous amount of neurons are operating in parallel at any analyses reveal zonal concentrations of Mn and Fe consistent given instance. Artificial neural networks are based on with early exposure to meteoric oxic fluids (NL cement - models of the human brain and behavior. They have proven Mn 32-68 ppm, Fe 80-103 ppm) and evolution of the pore helpful in recognizing patterns that can be attained by fluids through stagnation (bright cement) to two phases of learning through experience, and can be highly effective mixed meteoric-marine burial (dull cement - Mn 320-630 estimators of non-linear relations. ppm, Fe 1,570-3,620 ppm to bright cement - Mn 470-690 ppm, Fe 149-360 ppm). Multiple episodes of exposure to In this paper, porosity is estimated by applying neural meteoric-phreatic pore fluids occurred, as evidenced by the networks to attributes derived from seismic data. A number successive dissolution of aragonitic inner shellwalls of of wells are employed with the purpose of predicting porosity rudists. Cement zonations are correlative over great in the inter-well area, thus producing a 3-D map of porosity distances within one stratigraphic subunit of the upper from a 3-D seismic survey. After pre-processing, which Shu'aiba, suggesting the uniformity of meteoric-phreatic includes depth-to-time conversion of porosity logs and diagenesis. An understanding of porosity evolution is the calibration of synthetic seismograms to the seismic data to key to predicting reservoir quality in highly productive at each well location, relevant seismic attributes are extracted subunits of the upper Shu'aiba.

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from the seismic data. The network is then trained by presenting it with both the derived attributes from the seismic Enhanced Deconvolution of traces at the wells and with the measured porosity there. Saudi Arabian Seismic Data Porosity is then estimated in the inter-well area by applying the trained network to the entire seismic survey. Muhammad M. Saggaf and Roma A. Hergott Saudi Aramco Several network geometries and structures are investigated and evaluated, including feed-forward back-propagation and That reflection coefficients follow the white noise model is radial basis networks. Special smoothness constraints are one of the fundamental assumptions of conventional imposed on the networks in order to reduce the effect of deconvolution schemes, especially those based on optimal local minima and converge to a solution that represents the Wiener filtering (the most widely used technique in the smoothest model that fits data. This also helps to avoid the petroleum industry) such spiking and gap deconvolution over-fitting of the data. methods. In other words, reflection coefficients are assumed to be uncorrelated random variables, with a flat power The technique has been applied to seismic data in the spectral density and an auto-correlation function that is a Shedgum region of the Ghawar field in Saudi Arabia. The unit spike. However, analyses of well logs shows that in the network performance is evaluated through systematic cross- majority of cases reflectivity tends to depart from the white validation tests, in which one well is removed from the noise model, and to have a power spectrum that has a richer training set, the network training is carried out, and then the content of higher frequencies - a spectral behavior that is estimated porosity at the hidden well is checked against the often called "blueness". measured values there. The process is repeated for each well. These cross-validation tests indicate that neural networks, The assumption of white noise leads to a conventional can be effective at predicting porosity from seismic data, as deconvolution operator that can recover only the white the agreement between predicted and measured porosity component of reflectivity, thus yielding a distorted values is rather good. The method can be broadened further representation of the desired output. In this paper, a new by utilizing global optimization techniques like genetic stochastic model, fractionally integrated noise, is proposed algorithms. for modeling reflectivity. It is a model that more closely approximates the spectral character of reflectivity, and it Muhammad M. Saggaf holds a BSc encompasses white noise as a special case. The conventional in Mathematics (1989) from King deconvolution method is generalized based on this model Fahd University of Petroleum and in order to handle reflectivity that is not white. The technique Minerals and a MSc in Geophysics is implemented as a post-deconvolution spectral (1996) from the Massachusetts compensation filter that restores the non-white component Institute of Technology. His areas of of reflectivity that was removed by conventional interest include signal analysis, deconvolution. fractal models, wave propagation, inversion, neural networks, fuzzy The conventional and generalized deconvolution filters are logic, microprocessor architecture, analyzed by applying them to synthetic traces derived from and parallel computing. Muhammad is a member of the sonic and density logs of onshore and offshore wells in Saudi SEG. Arabia. Comparing the resulting output by the true reflectivity calculated from the logs shows that the Husam Al-Mustafa holds a BSc in generalized filter yields a significant improvement in the Geophysics (1988) from King Fahd accuracy of deconvolution, as indicated by the residual University of Petroleum and wavelet and RMS errors between the recovered and actual Minerals, and a MSc in Geophysics reflection coefficients. The generalized technique is also (1993) from Texas A&M University. applied to seismic data sections from north Saudi Arabia on His areas of interest include neural data that is characterized by relatively weak resolution and networks, rock properties, shear encumbered by low frequency noise. Visual inspection of wave propagation, and fractured the output shows a notable improvement in the sections in reservoirs. terms of enhanced event continuity, wavelet compression, signal resolution, and suppression of low frequency noise.

Muhammad M. Saggaf (see abstract "Attribute-Driven Porosity Estimation by Neural Systems" on page this for biography and photograph)

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Roma A. Hergott joined Saudi resulting categories by the training dataset and labeling the Aramco in 1980. Since 1992, she has classes accordingly. It is often called guided or directed held the position of Group Leader of classification, as it quantizes the input space into predefined 2-D Review Processing. She target classes. previously worked in seismic processing in Calgary, Canada with Both types of networks are implemented and used for the Digitech and Seiscan Delta. Roma automatic facies analysis of horizontal wells in Saudi Arabia. received her BSc in Mathenatics from Unsupervised networks provide a quantization, or zonation the University of Alberta in 1972. of the penetrated lithologies from which a geologist can start interpretation of the facies encountered in the well. This is done by examining the properties of the resulting classes and labeling them with the appropriate facies names. Automatic Log Facies Analysis Based on Supervised networks are first trained on the logs of a vertical Competitive Neural Networks well and the facies description derived from its cores. They are then applied on the logs of uncored horizontal wells in Muhammad M. Saggaf and Edgardo L. Nebrija the same sabkha for an automatic identification of their Saudi Aramco facies.

Manual interpretation of facies from well logs is a labor- These networks are easy to build and use, and produce results intensive process that involves the expenditure of a equivalent to those of a human log analyst at a fraction of considerable amount of time by an experienced well log the time needed for manual analysis. They are also relatively analyst, even with the aid of graphical techniques like cross- insensitive to incomplete or noisy data and exhibit the usual plotting. The problem becomes especially more difficult as neural network advantages of generalization, graceful the number of simultaneous logs to be analyzed is increased. degradation, and adaptability to parallel computing. Automatic methods that rely on multi-variate statistics are inflexible, require a large amount of statistical data, and often Muhammad M. Saggaf (see abstract "Attribute-Driven need complex dimension-reduction techniques like principal Porosity Estimation by Neural Systems" on page 149 for component and discriminant factor analyses to reduce the biography and photograph) problem to a more manageable size. These dimension- reduction techniques, however, are themselves compute- Edgardo L. Nebrija (see abstract "VSPs and 3-D Seismic intensive and inflict an unnecessary distortion of the input Pitfalls at Shaybah Field, Saudi Arabia" on page 136 for space. biography and photograph)

In this paper we propose to approach the problem of identifying facies from well logs though the use of neural Sequential Simulations of Porosity networks that perform vector quantization of input data by in a Carbonate Reservoir competitive learning. These are uncomplicated one-layer or two-layer networks that are small, compute-efficient, Ali Sahin and Saleem G. Ghori inherently well suited to classification and pattern King Fahd University of Petroleum & Minerals identification, and avoid the difficulties associated with back-propagation feed-forward neural networks; namely that Geostatistical simulation techniques such as Sequential their convergence is often unreliable, they have a Gaussian Simulation (SGS) and Sequential Indicator monotonous generalization behavior (overfitting, large Simulation (SIS) were developed recently and have now networks often perform worse than smaller ones on test become popular in simulation of both continuous and discrete data), require a considerable amount tweaking for the variables. These techniques have several advantages network geometry and choice of activation functions, and including automatic handling of both isotropies and data lack biological plausibility. conditioning, as well as fast computer implementation. SIS has an advantage over SGS in that it does not require any Competitive networks can be used in either an unsupervised assumption about the distribution of data. or supervised manner. Unsupervised learning looks for structure in the data without requiring a training dataset. Both SIS and SGS techniques were applied to simulate the This mode is often called feature-discovery or a "let-the- porosity distributions within a carbonate reservoir in Saudi data-talk" scheme. It performs clustering, or quantization Arabia. The results revealed that the realizations generated of the input space, but the resulting classes are unlabelled. by SIS have a wider range of variability than those generated Supervised learning imposes structure by calibrating the by SGS. The histograms and the variograms of the input

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data were reproduced more satisfactorily with the SGS Statistical Distributions and Correlation technique. However, the SIS technique was employed since different correlation ranges existed for different porosity cut- of Petrophysical Parameters in a off values. Also, the use of indicator classes in the SIS Carbonate Reservoir technique assists reservoir engineers to focus on the range of values which are critical in predicting reservoir Ali Sahin, Salih Saner and Hany F. El-Sahn performance. Therefore, the SIS technique appears to be King Fahd University of Petroleum & Minerals more appropriate for the geostatistical simulation of porosity within the reservoir under consideration. Statistical analysis of petrophysical parameters and correlation between these parameters are extremely Ali Sahin is currently working as an important in characterization of carbonate reservoirs. This Associate Professor at the Research study demonstrates how these tools can be used effectively Institute of King Fahd University of to characterize the Arab-D reservoir in the Abqaiq field Petroleum and Minerals (KFUPM) located in the Eastern Province of Saudi Arabia. Extensive in Dhahran, Saudi Arabia. He is data sets consisting of well-log porosity, core porosity and involved in various research projects core permeability values from the productive zones (Zone in the field of petroleum reservoir 1, Zone 2, and Zone 3) of reservoir and lithology indicators characterization and mineral deposit from Zone 1 provided the basic data for the study. evaluation. Ali received his BSc (Honors) in Mining Geology and Statistical analysis revealed that the well-log porosity and PhD in Applied Geostatistics from the University of Leeds. the core porosity distributions of respective zones are almost After his graduation in 1977, he joined the Mineral identical with core porosity distributions having slightly Exploration and Research Institute (Ankara, Turkey) as a higher mean values. This can be explained by possible bias Senior Geologist. During his stay in Ankara, he also served in core selection and differences in the conditions of as a Faculty Member at the Department of Mining and measurements. The porosity distribution for Zone 1 is Petroleum Engineering in the Middle East Technical approximately normal reflecting a mixed lithologic University. Ali joined the Department of Earth Sciences at framework within this zone. However, due to grain- KFUPM in 1982, where he taught courses in Geostatistics, dominated sediments associated with mainly high porosity Economic Geology and Computer Applications in Geology, values, the porosity distribution for Zone 2 displays and participated in the supervision of 14 MSc students. He asymmetry with a negative skewness. On the other hand, also served as a member of the Editorial Board of the due to mud dominated sediments exhibiting low porosity in Arabian Journal for Science and Engineering. Ali is a Zone 3, the porosity distribution is asymmetric with a member of the Institution of Mining and Metallurgy, Turkish positive skewness. Geological Society and the Dhahran Geological Society. The general pattern of permeability distribution for each Saleem G. Ghori received his BSc zone on the logarithmic scale is similar to that of the in Petroleum Engineering from the corresponding porosity distribution reflecting some degree University of Engineering and of correlation between porosity and permeability. The Technology, Lahore, Pakistan. He corresponding distributions of vertical and horizontal core received his MSc and PhD degrees permeability values are similar, but their averages are from the New Mexico Institute of different. The average horizontal permeability values within Mining, USA, both in Petroleum both Zone 1 and Zone 2 are considerably higher than the Engineering. After graduation in corresponding averages for the vertical permeability. 1992, he worked as a Research However, the reverse is true in Zone 3 with the average Associate in the Petroleum vertical permeability being slightly higher than the average Engineering Department of the University of Texas at Austin. horizontal permeability. Saleem joined the Research Institute at the King Fahd University of Petroleum and Minerals in November 1993. The correlation plots between the core porosity and core His research interests are geostatistics, reservoir flow permeability on semi-log paper and regression analysis simulation, tracer technology and parallel processing revealed relatively poor correlation between these variables computers. He is a member of the SPE. with the correlation coefficient being less than 0.7 for all zones. The correlation diagrams for the core porosity and the core permeability within each lithology in Zone 1 indicate that the lithologic control on porosity is not very significant in this zone.

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Ali Sahin (see abstract "Sequential Simulations of Porosity The main phases that have affected this area are the in a Carbonate Reservoir" on page 151 for biography and Hercynian and Autrichian orogenies. The effects of the photograph) Hercynian orogeny are characterized by significant erosion in Paleozoic time. In the Early Mesozoic, the area was Salih Saner is an Associate Professor affected by broad subsidence resulting in the formation of a at the Research Institute of the King broad basin. Fahd University of Petroleum and Minerals (KFUPM) since 1981. He In order to develop a structural and tectonic appraisal of the has 21 years of experience in the Talemzane block two directions (northeast-southwest and petroleum industry and research with northwest-southeast) of the megaregional cross- section and specialization in petroleum geology geological cross-section were used. Also a satellite image and formation evaluation. Salih study of the Talemzane block and depth map was used to received his PhD in Geology from the determine the structure and deformation along the study area University of Istanbul in 1977. He and extrapolate the information southward into the Hassi worked as an exploration geologist with Turkish Petroleum R'mel block and eastward into the Mehaiguene block. Corporation for six years before joining KFUPM. Currently, Salih is associated with the Petroleum and Gas This approach improved our understanding of the basin Technology Division at the Research Institute as the leader architecture and the planning of future seismic and of the Geology and Group. Geological basin exploration activities. analysis, reservoir modeling, well logging, rock and pore characterization, and petrophysical studies are the fields of Cherifa Sakher graduated from the his interest. He has about 30 publications in these fields. University of Algeria in Geophysics Salih is a member of the AAPG, SPE, SPWA, Society of Core in 1992 after which she studied Analysts, Association of Turkish Petroleum Geologists, and petroleum exploration at the Institut the Chamber of Turkish Geological Engineers. Algerieu du Pétrole for a year. Cherifa joined Turkish Petroleum Hany F. El-Sahn is currently Corporation in 1996 for six months working as a Scientist at the Research and was involved in hydrocarbon Institute of King Fahd University of exploration and assessment of some Petroleum and Minerals (KFUPM). blocks in Algeria. She is presently He received his MSc degree in Earth Geophysicist Engineer with Sonatrach Exploration on a Sciences from KFUPM in 1992, and variety of exploration projects, one of which was the his BSc degree in Geology from Cairo interpretation of the giant Algerian gas field Hassi R'mel. University in 1984. Since joining the Her research interests include the processing and the seismic Research Institute in 1992, Hany has interpretation on Workstation "Charisma". participated in several geological and petroleum engineering projects. His areas of interest Farida Benatmane graduated in include regional geology, carbonate facies analysis, Geology from the University of micropaleontology, and computer aided modeling. Hany is Algeria in 1991. She also studied the co-author of several publications in the fields of geology, Petroleum Geology at the Institut geostatistics and computer programming. Algerien du Pétrole. Farida worked with Sonatrach Division Exploration in 1994 on various interpretational Structural Evolution by Mega-Regional geological projects and is currently Geologist Engineer with the Seismic in the Northwest Triassic Basin company. She is interested in (Block 409) sedimentology research.

Cherifa Sakher and Farida Benatmane Sonatrach Exploration AGU Spring Meeting

The Triassic reservoirs constitute the main plays with the 26-29 May, 1998 development of the trias argilo-greseux that produce in Hassi For more information please contact: R'mel giant gas field. From the tectonic viewpoint this area AGU Meetings Department has a structural style associated with major faults trending 2000 Florida Avenue, NW northeast-southwest or north-south. Washington, DC 20009, USA Tel: (202) 462-6900; Fax: (202) 328-0566

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the microbial mats. Coarse- to medium-crystalline dolospar Facies and Diagenesis as Controlling occurs either as primary pore-filling or as replacement of Factors on Reservoir Quality of the pore-filling calcite. In general, dolomitization enhanced the Proterozoic-Cambrian Ara Group porosity of the carbonates. Carbonates (South Oman Salt Basin) During successive diagenetic stages several processes Stefan Schröder, Albert Matter, Karl Ramseyer affected the dolomites. The diagenetic sequence can be University of Bern subdivided into an early dolomitization with positive effects and Joachim E. Amthor on porosity, and a late succession of both porosity creating Petroleum Development Oman and destroying processes. Leaching and formation of fractures were porosity creating processes. Porosity The Ara Group of the South Oman Salt Basin attracts destroying processes include cementation by evaporites renewed interest by exploration because of its hydrocarbon (halite, anhydrite) and bitumen, as well as partial de- potential. It comprises a cyclic sequence of dolomite dolomitization and silica replacement of anhydrite. reservoirs, prolific source rocks, and evaporite seals. Due Destructive processes dominated during late diagenesis. to deep erosional truncation in post-Ara times no surface Initial porosity was controlled by facies distribution and most exposures are available. Subcrops of the Ara Group are probably increased from supratidal sabkhas to subtidal confined to the interior of Oman where it was deposited in shoals. During diagenesis lithologies with high initial several evaporitic basins, one of them being the South Oman porosity (e.g. bioherms) were cemented preferentially, Salt Basin. The study focuses on (1) the facies evolution whereas lithologies with moderate initial porosity (e.g. in through time as a basis for a sequence stratigraphic analysis, inter- to subtidal microbialites) remained unaffected. and (2) the degree to which the diagenetic evolution controls reservoir quality, with the aim to predict reservoir quality Stefan Schröder received his MSc in distribution. Geology from Würzburg University, Germany in 1997. He worked on The Ara Group (Late Proterozoic to Early Cambrian) Pliocene clastic sediments and consists of a thick (3 to 4 kilometers) sequence of evaporites neotectonics in Italy before joining (sulfates, halite and potash salts) deposited during more Bern University. Stefan is currently restricted phases, and dolomites that represent more open working on his PhD on marine conditions. In a typical succession, basal dolomites sedimentology and diagenesis of are followed by thin anhydrite and thick halite, again overlain subsurface Proterozoic/Cambrian by anhydrite. The cyclic repetition of this succession reflects carbonates and evaporites from recurrent changes in salinity and sea level. Oman.

The almost complete dolomitization of the rocks has Albert Matter and Karl Ramseyer (see abstract "The Athel obliterated much of the depositional fabric. However, some Play in Oman: Controls on Reservoir Quality" on page 62 remaining features allow reconstruction of the general for biography and photograph) depositional environment. Microbialites are most conspicuous, and their presence indicates a deposition in a Joachim E. Amthor (see abstract "Sedimentology, peritidal setting. Due to the lack of grazing organisms, the Diagenesis and Charge History of the Haima Deep Gas microbes could have colonized even the deeper subtidal Reservoirs in North Oman: An Integrated Approach to Play areas. Observations on slabbed cores suggest a gradual Evaluation" on page 60 for biography and photograph) transition from more or less stratiform mats, often associated with sabkha-anhydrite, that are typical of inter- and supratidal areas, and dome-shaped small biohermal Late Triassic Evaporite and Pre-Triassic constructions forming subtidal shoals. Their internal fabric Strata: Potentials for Future can be highly variable and they show only minor occurrences of evaporites. Hydrocarbon Prospects in Lebanon

Isotope data suggest that dolomitization as the main Mars E. Semaan diagenetic process occurred during and/or shortly after Lebanese American University deposition. The microfabric of Ara carbonates comprises mostly fine-crystalline dolomite with intercrystalline Indications of the presence of Triassic evaporites beneath porosity developed during the transformation of micritic Lebanon, in the eastern side of the Levant in the calcite to dolomite. Anhedral crystals are associated with Mediterranean is documented. In 1993, a marine seismic survey in northern Lebanon, and covering the widest part

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of the continental shelf, showed deeper structural horizons with a high velocity below the Jurassic, which with further A High Resolution Sequence analysis may confirm the presence of deeper evaporites. Stratigraphic Study of the These Jurassic successions contain intervals of carbonates Callovian-Early Kimmeridgian and evaporites, henceforth showing potential existence for Shuqra Formation in the Aden-Ahwar Area non-flushed biodegraded accumulations under anhydrite of Coastal South Yemen seals. These horizons were correlated with the salt deposits in the Kura-Chine basin of the Palmyrides. John D. Smewing Earth Resources Ltd., UK The Triassic successions are believed to be a continuation Abdul R. Saeed and Abdul M. Ahmed of the west-southwest trend of the adjacent Palmyride Basin Ministry of Oil and Mineral Resources, Yemen of Syria. This trend also suggests that the basin axis is west- southwest and continues toward Egypt, with its thickest The Shuqra Formation forms part of a widespread section present in northern maritime Lebanon. The transgressive carbonate succession overlying the Kohlan Palmyride Basin is well-known from subsurface exploration sandstone and basement in south Yemen. In order to better and drilling, where a number of Triassic oil and gas understand the distribution, development and geometric discoveries were made. relationship of its constituent lithofacies, an outcrop-based, high-resolution sequence stratigraphic study has been carried Regional considerations with regard to distribution and trend out on the Shuqra Formation in the Aden-Ahwar area of of the Kura-Chine salt basin, may be correlated with the coastal south Yemen. westward extension across the Levant Transform fault under north Lebanon. These deposits are then expected to be This has involved the correlation of twelve measured present under the northern part of Lebanon. Thus a sealing, stratigraphic sections along a regional east-west dip line. potentially prospective pre-Jurassic subsurface successions The results of this analysis have shown that the Shuqra was seems to be firmly established for Lebanon. deposited on a southeast-facing, clastic-influenced homoclinal carbonate ramp and that it contains five This paper will attempt to shed some light on these probable lithofacies representing delta plain to mid-outer ramp Triassic evaporites which may hold the future of oil and gas environments. The distribution of lithofacies on this ramp prospects in Lebanon. The fractured and eroded younger was controlled by long-term variations in relative sea level rocks of Lebanon suffered fresh water flushing which has and not by short-lived localized tectonics. Based on the removed any hydrocarbons present. However, the Upper correlatable vertical stacking pattern of these lithofacies and Triassic evaporites and the pre-Triassic strata still hold the identification of key surfaces, the Shuqra can be divided unflushed oil reservoirs. This is the proposed theory. into three unconformity-bound third order depositional Additional geophysical data and reprocessing of the 1993 sequences. The Kohlan sandstone is found in the lowest marine data from offshore Lebanon may be necessary to part of the lowermost sequence. The base Madbi comprises prove this theory. the lower part of an overlying fourth sequence. Mars E. Semaan received his MSc Potential for source rock development exists in the degree in 1978 and PhD degree in transgressive portions of the Shuqra sequences. Porosity in Physics in 1982 from Texas Christian the Shuqra at outcrop is minimal. However, grainy inner University. Mars is currently an ramp carbonates were developed in the highstand systems Assistant Professor of Physics at the tracts and these may be expected to have intergranular Lebanese American University in porosity in the subsurface. The sequence boundary at the Byblos. He also worked with PT top of the Shuqra was subaerially exposed and secondary Caltex Pacific Indonesia between porosity can be anticipated in the underlying limestones. 1991 and 1996 and as Geophysicist The Kohlan sandstone is clean and generally only poorly to with Texaco's Exploration and moderately cemented. Production Division between 1982 and 1991. His interests are related to hydrocarbon prospects in Lebanon. Mars is John D. Smewing is currently a member of the API, AAPG, IPA and SEG. Director of Earth Resources Ltd., UK. He received his BSc degree in GSA Annual Meeting Earth Sciences and Chemistry with 26-29 October, 1998 Honors from Leeds University in 1971, and PhD in Earth Sciences For more information please contact: from the Open University in 1975. GSA Meetings Department Following an early career in Tel: (303) 447-2020; Fax: (303) 447-1133 ophiolite studies, John established

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the Earth Resources Institute in 1980 and now directs a Usually, level-by-level interpretation schemes are used in number of international outcrop-based projects for the oil log analysis. Electrical measurements at each logging depth industry. level are used to interpret multiple formation parameters including the depth of the invasion zone and the resistivities Abdul R. Saeed graduated in of the invaded and uncontaminated formation. Only the Geology from Qatar University in combination of multiple measurements will yield reliable 1985 and has since been working as estimates for these parameters. Additionally, when a Geologist with the Ministry of Oil combining galvanic and induction measurements, one can and Mineral Resources in Sana'a, also use the inherent bias of each measurement to Republic of Yemen. His work has compensate for the weakness of the other and obtain a unified involved secondment to a number of significantly less biased and thus more realistic operating companies in Yemen where interpretation. Although this process is very beneficial in his duties have included field and well delivering a less biased interpretation it further increases site geology, gravity and seismic computational requirements. surveying and seismic interpretation. He has been a member of the Reevaluation Data Committee in PEPB and Chairman One way of addressing the computational constraints is by of Al-Bakri Oil Company. using massive parallel supercomputers which even in one processor mode reduces the computational time by one Abdul M. Ahmed completed his MSc decade leaving enough room for speed improvements in Geology at Baku, Azerbaijan in through code parallelization and special algorithms. Another 1981. He has been working with the way of addressing the heavy computational requirements is Ministry of Oil and Mineral to replace the conventional two-dimensional inversion with Resources in Sana'a, Republic of a special rapid computational scheme where the two- Yemen since 1982. His work has dimensional calculations are broken into a sequence of one- involved secondment to a number of dimensional ones. This process converges to the real two- operating companies in Yemen where dimensional solution approximately tens to hundreds times his duties have included field and well (model complexity dependent) faster than the conventional site geology, stratigraphic two-dimensional schemes. Yet another decade of speed correlation and seismic interpretation. He has acted as improvements of the rapid two-dimensional inversion is Ministry Geologist Representative for Hunt Oil Company. being achieved by using neural net type techniques.

The two-dimensional inversion delivers not only the two- Limits and Possibilities Determining Rt dimensional distribution of the formation parameters but also statistics which are essential for estimating the reliability with Array Resistivity Logging Tools of the results. Errors give an idea about the fit between the interpretation and the real data. Error bounds can give the Kurt M. Strack, Michael A. Frenkel possible range of the interpreted parameters and can be and Alberto G. Mezzatesta translated directly into maximum and minimum pay. The Western Atlas Logging Services importance of each parameter can tell whether or not the data is sensitive to any changes in this parameter and thus In locating hydrocarbon-bearing formations in a borehole, false interpretations can be avoided. electrical logging techniques play a key role by distinguishing between oil and water saturated rocks. Among Case histories for different tools and applications clearly the electrical techniques both classes, induction and current show the benefits of the new concept of integrating multiple injection (galvanic) tools, are of significant importance in resistivity logs. determining movable and residual hydrocarbons. Over the years, substantial effort has been put into the tool design to Kurt M. Strack received a MSc from obtain the best possible apparent readings representing the the Colorado School of Mines and a formation resistivities. Unfortunately, with more complex PhD from University of Cologne, environments such as dipping beds, deep invasion and thin Germany. He is presently Chief beds, significant interpretation must be done to avoid false Scientist at Western Atlas Logging analysis. The most objective way is the use of geophysical Services (WALS) after being inversion which gives good reliable formation parameter Manager of the Advanced Scientific estimates. Research and the Resistivity Product Line where he developed several of WALS’ new technologies. Prior to

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WALS Kurt worked as Geophysical Consultant, as university An Integrated Approach to researcher and teacher (9 years in Cologne), as R&D Manager in the geothermal and logging industry. Kurt has Najmah-Sargelu Formation Fractured published over 100 publications, one textbook and several Carbonate Reservoir Prediction patents. He also received a Fulbright scholarship and (Upper to Middle Jurassic) numerous international grant/awards throughout his career. in the Gotnia Basin of Kuwait His main interest is integrated geophysics, inversion, and technology transfer and project development. He is a Christian J. Strohmenger, Steven R. Webb member of the SPWLA, AAPG, ASEG, DGG, BDG, SPE, Exxon Exploration Kuwait Inc. SEG and EAGE. Jassim M. Al-Kandari, Kuwait Oil Company Jonathan Kaufman and James M. DeGraff Michael A. Frenkel received a MSc Exxon Production Research Company degree in Applied Mathematics in 1978 from the Moscow Institute of the The information presented in this paper is based on the Oil and Gas Industry and a PhD in results to date of a joint technical study between Kuwait Oil Physics and Mathematics in 1984 Company and Exxon Exploration Company. A from the USSR Academy of Sciences, multidisciplinary approach was used to analyze and predict Moscow. He worked for 20 years in reservoir quality distribution in Mid to Upper Jurassic geophysics as a Scientist on the carbonates of the Najmah and Sargelu formations in the development of numerical methods Gotnia Basin of southwestern Kuwait. The carbonate strata and software for processing, were deposited in low to moderate energy, inner to outer modelling, inversion of electromagnetic and potential fields, ramp/basinal environments, and are overlain and underlain well logging tool design and data interpretation. In 1992, by excellent regional seals. Fractures critical to reservoir Michael joined Western Atlas Logging Services where he is performance were created in part by multiple tectonic events presently working as Senior Scientist on the development of related to convergence and collision between the Arabian fast inversion methods and software for well logging data and Asian Plates, followed by periods of plate relaxation. interpretation. Michael has published over 30 scientific In addition, maturation of excellent source rock in the upper papers and twobooks. He is an active member of the SEG, Najmah Formation has generated near-lithostatic SPWLA and AGU. overpressures that probably contributed to fracturing. The economic viability of the reservoir depends on the Alberto G. Mezzatesta received a distribution of matrix porosity in addition to the fracture PhD from the University of Houston networks. Disciplines used in the study include sequence and a diploma in Petroleum stratigraphy, 2-D and 3-D seismic interpretation, Engineering from the University of petrophysics, petrography, fracture description and analysis, Cuyo, Argentina. Alberto joined basin history modeling, geochemistry, and reservoir Western Atlas in 1984 where he is modeling. presently Manager of Research Support with the responsibility of The sequence stratigraphic framework developed in this supporting the development of new study divides the section into two second-order sequences. technologies with modeling and In the lower sequence, a transgressive systems tract (TST) inversion capabilities. Prior to this, he was a Project Leader overlies the top-of-Marrat sequence boundary (SB), and in for the development of the integrated interpretation of turn is overlain by a highstand systems tract (HST) on top resistivity measurements using inversion methods, and was of an intra-Dhruma maximum flooding surface (MFS). A heavily involved in the development and deployment of the second sequence boundary is placed near the top of the new resistivity technology. Prior to joining Atlas, Alberto Sargelu Formation. In the upper sequence, a second MFS was Head of the Reservoir Simulation Group in the National separates the TST and HST within the Najmah Formation. Oil Company, Argentina, where he worked in the areas of The HST displays a sequence boundary at the top of the reservoir engineering, reservoir simulation, petrophysics clean Najmah limestone and is overlain by transgressive and well log interpretation. Alberto’s areas of expertise are “Upper Najmah Shale” (condensed section). Detailed core log interpretation development software, petrophysics, to well-log ties allow further subdivision of the systems tracts borehole geophysics, reservoir engineering, and reservoir into Sargelu early highstand systems tract, Sargelu late simulation. He is an active member of the SPE, SPWLA, highstand systems tract, Najmah early transgressive systems and SEG and has authored several publications and presentations at international symposia.

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tract, Najmah late transgressive systems tract, Najmah early Jassim M. Al-Kandari received a highstand systems tract, and Najmah late highstand systems BSc in Geology from Kuwait tract. The best matrix reservoir quality exists within the University in 1995 and joined Kuwait Najmah highstand systems tract and the Sargelu late Oil Company (KOC) the same year. highstand systems tract. Jassim is presently a Geologist with KOC working in the Exploration and Fracture analysis based on core observations indicates that Development Group. He worked six nearly all effective fractures are vertical and partly filled months on a loan assignment with with calcite and sometimes bitumen. The open apertures of Exxon Exploration Company in some fractures exceed one centimeter and are likely held Houston, Texas. open in the subsurface by the near-lithostatic pressures and irregular distribution of cements that act as natural propants. Jonathan Kaufman has over 16 The highest fracture densities are in relatively clay-free, low years experience in carbonate total organic carbon content, low porosity packstones and reservoir characterization, with 9 of wackestones near source rock intervals in the Najmah and those years being at Exxon extending downwards into the upper Sargelu. Fractures in Production Research Company in these lithologies generally terminate abruptly against Houston Texas. Jonathan has been argillaceous or organic-rich strata. Based on fracture involved in sequence/seismic orientations determined from paleomagnetically oriented stratigraphy, facies analysis, and core, image logs, production data, and seismic interpretation, reservoir quality studies of carbonate we conclude that the fractures formed as a combined product reservoirs from the USA, Canada, of overpressure generation and tectonism related to Russia, China, Mexico, West Africa, Indonesia, and the movement of the Arabian Plate. Middle East. He is presently a Senior Geologist in the field studies group at Sonat Exploration Company in Houston, Christian J. Strohmenger received Texas. a Diploma in Geology from the University of Giessen and a PhD in James M. DeGraff received a BSc in Mineralogy/Sedimentology from the Geology (1975) and an MSc in University of Heidelberg, Germany. Geophysics (1976) from Michigan From 1989 to 1990 he worked as a Technological University, and a PhD Research Assistant in carbonate in Structural Geology from Purdue sedimentology and sequence University (1987). After joining stratigraphy at the University of Exxon Production Research Geneva, Switzerland. Christian Company in 1988, he worked on the joined BEB Erdgas und Erdoel GmbH, Hannover, Germany prediction of fractured reservoir in 1990, working as a Carbonate Sedimentologist until 1994, quality in a variety of reservoir types and as a Seismic Interpreter until 1996. In 1996 he accepted and structural settings around the world. His current a foreign assignment as an Exploration Geologist with assignment involves predicting fractured reservoir quality Exxon Exploration Company in Houston, Texas, where he in Jurassic carbonate reservoirs of Kuwait. James has is currently working on carbonate reservoirs of Kuwait. published numerous papers and abstracts on a variety of Christian has published papers on a variety of topics, topics including fracture formation in fold-thrust belts and including carbonate sedimentology, sequence stratigraphy, volcanic rocks, mechanical modeling of folds and faults, and reservoir quality prediction. and fractured reservoir quality in carbonates, basement rocks, and tight sandstones. Steven R. Webb received his BSc degree in Geology in 1973, and MSc degree in Geology in 1975, both from Texas Tech University in Lubbock, GEO’98: Short Course Texas. Since that time he has worked Fractured Reservoir Characterization as an Exxon Geoscientist in a wide and Modeling variety of exploration and production 18-19 April, 1998 projects in numerous carbonate For more information please contact: provinces around the world. From Mr. Eric Gross, IFP Arabian Gulf, 1994 to present, Steven has been P.O.Box 3282, Manama, Bahrain working the Middle East with more recent focus on Kuwait. Tel: (973) 214-778; Fax: (973) 217-908 He is currently a member of the Kuwait team working the e-mail: [email protected] Kra Al-Maru Joint Technical Study in Western Kuwait.

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State-of-the-Art 3-D DMO Eric Suaudeau is currently R&D Geophysicist with Compagnie Générale de Géophysique. He also Eric Suaudeau, Philippe Herrmann worked with Informatique Pétrolière and Bernard David Scientifique from 1990 to 1992. Eric Compagnie Générale de Géophysique received his MSc in Physics in 1983, and PhD also in Physics in 1987 from Amplitude and phase preservation are nowadays becoming Orsay University. He also holds a standard requirements for DMO processing of 3-D seismic Post-Doctorate degree from the surveys. In this respect, the inherent wide distribution of University of Florida. His offsets and azimuths associated with land and OBC surveys, professional interests are seismic processing and software and also wide-tow marine surveys represent a challenge to engineering. conventional DMO algorithms. Several prerequisites are necessary in order to fulfil these preservation requirements, Philippe Herrmann has been with such as proper weighting of the DMO operator and Compagnie Générale de frequency filtering of the same operator to remove aliasing Géophysique since 1992 and is noise. It has been shown that a key factor in the preservation currently R&D Geophysicist. He of signal phase and amplitude is the application of a received his PhD in Geophysics from weighting that compensates for the field geometry. A large Delft University in 1991. Philippe is variety of weighting techniques have been proposed that a member of the SEG and EAGE. His significantly reduce acquisition footprints. Nevertheless professional interest is seismic practice shows that, even after proper weighting, artifacts processing. still remain, which compromise the quality of the result and reduce the reliability of the data for further AVO studies. Bernard David is a Geophysicist and These artifacts are related to the crude binning procedure has been working with Compagnie applied to the DMO-generated traces in conventional Générale de Géophysique since algorithms. The Kirchhoff algorithm is generally applied 1981. He received his MSc in Earth for a constant-velocity model. Under such an assumption, Science from Paris VII University in the DMO operator is a 2-D operator which generates traces 1976. Bernard's professional interest that are regularly sampled along the source-receiver is seismic processing. segment. Traditionally DMO traces falling inside a bin are moved to the center of the bin, irrespective of their true position. This corresponds to a nearest-neighbor interpolation scheme, which, by smearing the DMO operator in the transverse direction, has the effect of aliasing the data and decreasing the spatial resolution. Development of a Complex Sand-Shale In order to reduce the aliasing noise thus induced, traces Reservoir: A Case Study of the have to be properly interpolated to the neighboring bin Wara Formation in the Minagish Field, centers. This is achieved by convolving each of the DMO- West Kuwait generated traces with a band-limited interpolation filter along the line and CDP directions. The benefits of 2-D band limited Dogan Sungur, Kuwait Oil Company, spatial interpolation are manifold: (1) increase in spatial O.E. Ibe, BP Kuwait, resolution, (2) better preservation of signal phase and Abdullah Bouhamad, Kuwait Oil Company amplitude, and (3) greater signal-to-noise ratio. and Arshad Waheed, Halliburton Services, Kuwait

We illustrate the improvements brought about by this method The Wara Formation in the Minagish field of west Kuwait on both synthetic and field data (notably from the Middle is of Upper Cretaceous, Cenomanian age. The formation East). We show that footprint artifacts observed after DMO consists of a series of alternating fine-grained marine sand are mostly a spurious effect of the spatial interpolation and gray shales cut by younger channel deposits. Detailed scheme conventionally used. These artifacts can be removed stratigraphic interpretations and channel sand correlations at a reasonable computation cost. Furthermore this procedure provide strong evidence that flooding events and channel can be applied to any acquisition geometry. It is model- sand development can be combined into four distinctive and independent and fully compatible with any DMO weighting vertically stacked stratigraphic sequences. The channel scheme. sandstone exhibits good reservoir quality while the marine sands essentially possess non-commercial characteristics.

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Preparing a geological map, charting the course of the pay in Natural Gas Engineering from Texas A&I University and horizon and defining commercial reserves of the Wara a DEng in Petroleum Engineering from the University of reservoir in the Minagish area has been a challenge primarily Southern California. due to uncertainties in reservoir continuity. Abdulla Bouhamad received his BSc In addition to the geological challenges, sustaining stable in Petroleum Engineering from West production from this horizon has been difficult in the past. Virginia University in 1980. Abdulla Measured oil gravity average 19 degrees API while average has 12 years experience in petroleum reservoir pressure is 2,500 psi. Production tests from seven engineering and 3 years in reservoir completions showed unstable rates between 85-350 bopd at engineering. He is currently the low wellhead pressures. It is suspected that the high viscosity Superintendent of Field Development oil and low formation pressures were the primary with Kuwait Oil Company. impediments to sustained productivity.

The challenge to develop this reservoir led to the implementation of two pilot programs to evaluate alternative Arshad Waheed is a Technical completion and stimulation techniques for sustaining Advisor with Halliburton Ltd., productivity in the Wara channel sands. A horizontal well Kuwait. He has been with was drilled and completed in Channel 1 while a propped Halliburton for 13 years working in fracture stimulation was performed across Channels 1-3 in stimulation, cementing, tools and an existing well. Both pilots aimed to increase the flow testing services at various locations potential of the wells by enhancing the permeability over this period. Arshad holds a BSc thickness and conductivity respectively. degree in Petroleum Engineering from Texas A&M University. Preliminary results obtained from the pilots showed sustained rates of 1,750 and 2,750 bopd respectively from the horizontal and fracture stimulated wells compared to a maximum of 350 bopd tested in an offset well. Although The Power of 3-D Seismic During extensive tests will be required to confirm initial results, Exploration: Successful Drilling of plans are underway to drill a 7-well program to develop the reservoir. This paper details the methods applied to resolve Seismic Anomalies Rosetta Concession, geologic and engineering questions regarding successful Nile Delta, Egypt development of a complex sand-shale reservoir. John L. Swallow, Steven J. Maddox and Sinead Lynch Dogan Sungur is a Senior Geologist BG plc at Kuwait Oil Company (KOC). He has over 20 years of petroleum The Rosetta Concession was officially granted to a British experience including 4 years with Gas International Exploration and Production led consortium KOC, 7 years at AGOCO, Libya, 5 on 29th May, 1995. Previous licencees had left BG a legacy years in Norcen Oil, Calgary, of two non-commercial wells, Rosetta Northwest-1 and Canada, 2 years at Husky Oil Rosetta-2, and a pre-1980 grid of poor quality 2-D seismic Operation Ltd. Calgary, Canada and augmented by a few more modern (1986 to 1993) 2-D 5 years with Turkish Petroleum seismic lines. Based on these data a block wide review Corporation, Ankara, Turkey. Dogan identified several play types within the Pliocene and holds BSc and MSc degrees in Geology from Hacettepe Miocene and also generated a significant number of leads. University of Ankara, Turkey. With no firm prospects generated by autumn 1995, the O.E. Ibe is a Petroleum Engineering decision was taken to shoot the largest single 3-D seismic Consultant with British Petroleum survey then undertaken in Egypt (1,500 square kilometers) Exploration on secondment to to explore the most prospective parts of the block. The 3-D Kuwait Oil Company. He has 20 survey was shot in January 1996 and processing was years of reservoir and production completed in September 1996. engineering experience. Ibe previously worked for Mobil Oil E&P Pliocene anomalies were tentatively identified during in California and Gulf Coast regions processing and worked into prospects by placing the before joining British Petroleum in anomalies into a coherent geological framework and 1989. He holds BSc and MSc degrees quantifying their seismic response. This included the use

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of amplitude extractions, AVO analyses and modeling, and North Oman and are mature only in the Late Cretaceous/ the description of flat spots and other attributes. Tertiary foreland basin. Burial histories and thermal modeling indicate that generation started during Late Within two months of receiving the 3-D volume, the Cretaceous time and continues today. consortium was able to agree to drill one of the anomalies. Rosetta-3 was drilled in March 1997 and encountered the Natih oils have a distinct biomarker and carbon isotope three main gas-bearing sands as prognosed, with three DST's signature, which can be used to map their geographical flowing a cumulative rate of 60 mmscfg/d. distribution, and identifies other contributing oil types in mixtures. The Natih petroleum system is limited to central The story did not finish there. With high quality 3-D data North Oman, its maximum extent being structurally already available it was possible to switch directly from bounded, in the south by the peripheral bulge of the Late exploration into the development phase of the project. Cretaceous/Tertiary foreland basin and in the east by the Additional mapping based on the results of Rosetta-3 has salt-structured core of the Ghaba Salt Basin. The presence further refined our understanding of the subsurface. At the of a massive top seal and rather modest deformation in the time of writing Rosetta-3 lies within a development lease fold and thrustbelt of the Oman Mountains forces Natih oil and a three well back to back drilling program is underway. to migrate laterally.

John L. Swallow and Steven J. Maddox (see abstract "Plio- The volume of hydrocarbons generated by Natih source Pleistocene Clastic Reservoirs of the Offshore Nile Delta, rocks was calculated and compared to the estimated in-place Arab Republic of Egypt" on page xxx for biographies and oil to determine the trapping efficiency of the petroleum photographs) system. Some 100 billion m3 of source rocks is currently mature and generating oil and has produced a cumulative Sinead Lynch has spent four years volume of 14 billion m3 (100 billion bbls) oil. Natih oil-in- working in the oil and gas industry place amounts to 1.3 billion m3 (9 billion bbls), indicating with British Gas E&P. Sinead has that 9% of all generated hydrocarbons has actually been primarily worked in the Geophysical discovered. Currently 0.25 billion m3 (1.8 billion bbls) are Operations and Special Projects booked as recoverable reserves, equivalent to 1.8% of the Group which specializes in risk total generated volume. Both percentages classify the Natih reduction using seismic attributes. petroleum system as the most efficient system in Oman. Her areas of expertise include seismic The outstanding efficiency is due to the presence of an modeling, AVO and inversion and she excellent top seal and intra-formational source rocks, that has applied these technologies on have generated hydrocarbons since the Late Cretaceous. British Gas assets in North Africa, Southeast Asia and the UKCS. Remaining potential has been recognized in truncation traps on the northern flank of the foreland bulge and in possible turbidites in the foreland basin. The Natih Petroleum System Jos M.J. Terken (see abstract "Sedimentology, Diagenesis of North Oman and Charge History of the Haima Deep Gas Reservoirs in North Oman: An Integrated Approach to Play Evaluation" Jos M.J. Terken on page 60 for biography and photograph) Petroleum Development Oman

The Natih petroleum system is one of the smaller petroleum systems in Oman, measuring only some 20,000 square Makarem: The Giant Awakes - kilometers in areal extent. Resource volumes, however, are Progressively Deeper Exploration Reveals significant and amount to some 1.3 billion m3 of STOIIP. New Huqf Gas Play in Oman Most of the recoverable oil is concentrated in two giant fields, Fahud and Natih, which hold 145 and 100 million Graham J. Tiley, Joachim E. Amthor, 3 m respectively of 32° API oil. and Pascal D. Richard Petroleum Development Oman The Natih Formation consists of a 400-meter thick carbonate succession of latest Albian to Early Turonian age. Reservoirs The gas business in Oman is relatively young, but has made are comprised of heavily fractured, tight, chalky limestone rapid advances through a successful creaming of the Haima that produce mainly via the fracture network. Shaly (deep clastics) play in the Ghaba Salt Basin. Since the first limestone intervals in the Natih Formation contain Type II well drilled on the ‘Government Gas Sequence’ in 1985 organic matter. These source rocks are restricted to western some 19.5 trillion cubic feet (TCF) (550 billion cubic meters

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(BCM)) have been booked culminating in the signing of Fluid Communication Across a the Liquified Natural Gas agreement in 1996. To continue to meet growth targets of 1.0 to 1.5 TCF (28-42 BCM) of Major Fault Transecting the gas booking per year required the identification of a new 'Uthmaniyah Khuff Reservoir play. This challenge has been partly met with the drilling of Makarem-1 which reached its total depth of 5,079 meters Mark H. Tobey, William J. Carrigan, in August 1994. The well discovered gas in fractured Buah Peter J. Jones, Henry I. Halpern, dolomites of the Precambrian Huqf Group, in a large tilted Jaffar M. Al-Dubaisi, Mohammed A. Al-Amoudi and fault block with a closure of approximately 700 square Hani O. Al-Ohaily kilometers. The critical factor in the identification of the Saudi Aramco Makarem prospect was improvements in seismic data quality, in particular long-cable 2-D seismic surveys. Examination of 'Uthmaniyah Khuff-C gas/condensate compositional signatures indicates that: (a) over geological The reservoir flowed 600,000 m3/d of dry, sour gas on test, time, there has been slow fluid migration across a north- but despite the encouraging flow rates considerable south trending fault which transects the 'Uthmaniyah Khuff uncertainty remained over the long-term producibility of into two reservoir compartments; and (b) since production the reservoir and the degree of lateral connectivity. This began, this fluid migration has accelerated in the vicinity of issue was addressed through the development of a geological a well adjacent to the fault, presumably as a result of pressure model based on identification of analogues and through the draw-down at that well. prediction of fracture density from the fault system as defined on 3-D seismic. The resulting reserves booking of Prior to gas production at 'Uthmaniyah, the north-south 0.6 TCF (18 BCM) encompassed a 77 square kilometers trending fault acted as an effective barrier to fluid migration. area of the structure. There is an abrupt change in the chemical composition of fluids across the fault, most notably in H2S concentration. Initially two appraisal wells are planned, the first of which However, very slow fluid migration across the fault was spudded in September 1997, to pursue the remaining scope established over a geological time-scale, resulting in a of 2.6 TCF (76 BCM). The Makarem appraisal campaign gradient in the chemical and isotopic compositions of fluids offers considerable challenges both in terms of the High T west of the fault. The highest H2S concentrations of the drilling, logging and testing, as well as in maximizing original well-stream compositions west of the fault occur reserves bookings from widely spaced penetrations in a adjacent to the fault (5.0 to 5.5%) and decrease to 3.0% 10 complex reservoir. A program of multi-disciplinary work kilometers west of the fault. The H2S content at a well less is underway to improve the reservoir model, pulling together than 2 kilometers east of the fault is 9.3%. a wide body of work on Precambrian carbonates and addressing specific issues such as reservoir continuity and However, a recent sample collected from a well one the nature of the fault/fracture system. kilometer west of the fault shows a 1.4% increase in H2S compared to the original 1983 well-stream composition.

Graham J. Tiley received a PhD in Two other nearby Khuff-C wells show no increase in H2S Geological Sciences from the concentration over the production history of the field. The University of Birmingham in 1988. increasing H2S concentration at this one well attests to a He joined Shell in 1988 and was relatively recent, localized, one-way fluid communication posted to Shell Research in The across the fault in that vicinity, over the well's production Netherlands where he worked on history. Small, yet reproducible, differences in the seismic interpretation software condensate chromatographic signatures support that development. Graham was posted to conclusion. Shell in Nigeria in 1992 where he worked in both lateral prediction and Thus, over the production history of the field (approximately seismic interpretation. In 1996 he was posted to Petroleum 13 years), we observe an enormous acceleration in one-way Development Oman where he has been working on communication across the fault between two reservoir exploration and appraisal aspects of the Huqf play in North compartments. This one-way communication has been Oman. going on over geological time, but at a much slower rate. The accelerated communication is most likely due to the Joachim E. Amthor (see Abstract "The Athel Play in Oman: production-induced pressure draw-down west of the fault. Controls on Reservoir Quality" on page 60 for biography and photograph) Mark H. Tobey,William J. Carrigan, Peter J. Jones and Henry I. Halpern (see abstract "Geochemistry of Eastern Pascal D. Richard (see abstract "Integrated Haushi Saudi Arabian Paleozoic Gas/Condensates" on pages 79-80 Hydrocarbon Habitat Study in North Oman" on page 147 for biography and photograph) for biography and photograph)

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Jaffar M. Al-Dubaisi has been with the absence of reservoir analogues and in the presence of an Saudi Aramco since 1984. He is a extensive cemented fracture system; (3) significant problems Research Scientist with the Lab R&D calibrating wireline log response due to large amounts of Center of Saudi Aramco. He received organic material in the small pores; (4) design of deep, high a BSc degree in Chemistry from the pressure corrosion resistant well completions; and (5) design University of Tulsa in 1991. His of surface facilities to treat the sour gas production and to research interests include reservoir stabilize the volatile crude in an environmentally acceptable geochemistry. way.

In addition to the above, unstimulated production rates from the Al Noor field range between 40 and 110 m3/day. In order Mohammed A. Al-Amoudi and Hani O. Al-Ohaily (see to make the project commercial, higher well initials resulting abstract "Geochemical Evidence for Reservoir in higher recoverable volumes are required. To achieve this, Compartmentalization in Central Arabian Paleozoic different well designs such as massive hydraulic fractures, Reservoirs" on pages 96-97 for biographies and photographs) multi-laterals or multi-fracced multi-lateral wells, are considered. The first development wells will be hydraulically fractured. Extensive production tests before (barefoot) and The Athel Play in Oman: after fraccing are planned to accurately assess the productivity improvement factor of the fracture stimulation. Al Noor and Al Shomou Initially, 2 large (280 tones proppant) fractures are planned Field Development per well. However, a further improvement to one “mega” frac is considered if this stimulation technique is proven to Robert Turner, Michael O'Dell, Wouter Smits, be successful. Marcus Antonini, Elaine Leith, Sau-Wai Wong, Jean-Louis Alixant and Luc A.J. Vermin Given the combination of high pressure, high gas/oil ratio,

Petroleum Development Oman high CO2 and H2S content a unique combination of corrosion resistant sub-surface and surface material (e.g. Hastalloy, The Al Noor field (discovered in 1989) and Al Shomou field HPGRE and Alloy 28) is required to process the sour Athel (discovered in 1995) are located in the South Oman Salt crude in the facilities. A high- level integration between Basin, some 50 kilometers west of Nimr field. Light, volatile the surface engineers and the sub-surface team has proven oil (48° API) with associated hydrocarbon gas containing to be a key success factor in optimizing the design envelope

1.5 mol% H2S and 3 mol% CO2 are present in the Athel of the surface facilities and, as such, has contributed to Formation, a 400 meter-thick, silicilyte reservoir at a depth significant cost reductions. First oil production through the of approximately 4 kilometers. The infracambrian Athel surface facilities is planned by mid-2000. silicilyte consists mainly of micro-crystalline silica with porosity ranging from 15 to 25% and associated low matrix The Phase One development of the Al Noor field, together permeability of 0.02 microDarcy or less. The Athel silicilyte with a planned reserves booking in 1997 of the Al Shomou is unique in that it is both a reservoir and a world-class source field, will provide essential analogues for the maturing of rock, with Total Organic Content (TOC) upto 6 weight% future exploration discoveries in this unique silicilyte rock and hydrogen indices in excess of 400 milligram HC/g TOC. in Oman. The reservoirs are stratigraphically encased within salt and shale and are geopressured with a gradient of 19.8 kilo Robert (Bob) Turner graduated with Pascal/meter. To date six wells have been drilled in the Al a Chemical and Process Engineering Noor structure and four wells and side-tracks in the Al degree from Herriot Watt University Shomou structure. in 1974. He worked with Exxon, Amoco and Arabian Gulf Exploration Given this unique setting, and the nature of the fluid, major before joining Shell in 1980. Bob has multi-disciplinary challenges have to be met to optimize worked in Australia, Libya, UK, the economic oil recovery from the Athel silicilyte. A multi- Gabon, Holland and Venezuela in a disciplinary team (Exploration, Production and Surface variety of jobs mainly in Production engineering) was formed in Petroleum Development Oman Engineering and Well Operations. to address these challenges and to define a Phase One field Bob has played a key coordination role in development teams development plan as a precursor to a full development of for Rabi, Sole Pit and Urdaneta West fields. He is currently the Al Noor field. Major challenges to be addressed are: (1) the Asset Manager for the Athel development with a team seismic imaging and reservoir characterization of salt- comprising exploration, development and surface encased reservoirs based on Pre-Stack Depth Migrated 3-D engineering staff. seismic; (2) prediction of lateral reservoir connectivities in

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Michael (Mike) O’Dell has over 27 Sau-Wai Wong joined the Athel Team years reservoir engineering, as the Senior Production Engineer in supervisory, research and technical July 1997. Before coming to Oman, training experience with a U.S. major he worked for 3 years as a Petroleum and a Middle Eastern national oil Engineer in Sabah Shell Petroleum company. He has worked in reserve Company, Malaysia. Prior to that estimation, development planning, (1989-1994) Sau-Wai was with Shell reservoir simulation, production and Research in The Netherlands, where injection surveillance, and pressure he conducted research in rock analysis in both U.S. and mechanics. He holds a BSc (Honors) international operations, onshore and offshore. Mike is degree in Civil Engineering and a PhD degree in presently Senior Reservoir Engineer in the Athel Team in Geomechanics, both from the University of Manchester, UK. Petroleum Development Oman. Jean-Louis Alixant (see abstract "The Athel Play in Oman: Wouter Smits graduated with a MSc Controls on Reservoir Quality" on page 62 for biography degree in Structural and Economic and photograph) Geology from Utrecht University, The Netherlands in 1985. After joining Luc A.J. Vermin holds an ME in Shell at the end of 1995 he worked in Mechanical Engineering from the the UK (well site and operations Technical University of Eindhoven. geology), Holland (integrated He joined Shell International in 1989. reservoir studies for Nigeria) and Luc worked as Process Engineer in Brunei (Senior Reservoir NAM, Netherlands for 4 years. After Development Geologist in an moving to Petroleum Development integrated exploration and development team). Wouter is Oman as a Conceptual Engineer, Luc currently Senior Reservoir Development Geologist for the is currently Project Leader of the Athel Development in Petroleum Development Oman in an Athel Surface Facilities. integrated team comprising exploration, development and surface engineering.

Marcus Antonini is currently Senior Development of the ‘Slip-Sweep’ Seismic Interpreter in Petroleum Seismic Acquisition Technique Development Oman's (PDO) Athel Development Team working on Jan Wams and Erik Kleiss reservoir characterization in Al Petroleum Development Oman Shomou and developing the Athel exploration portfolio. Marcus The idea behind slip-sweep recording is unnervingly simple: worked as a Seismologist from 1986 a vibrator group starts sweeping without waiting for the other to 1989 and joined BEB Oil & Gas group’s sweep to be completed. After correlation, a long Co. in Germany in 1989 as an composed record will result, which can be cut at the Exploration Geophysicist. In 1995 he was transferred to appropriate time-zeroes to extract the individual correlated PDO's Exploration Unit working in the Ghaba Salt Basin, records. North Oman. Since 1996 Marcus has been working in frontier Athel exploration, South Oman dedicated to the If this technique can be put into production, the benefits are acceleration of reserves additions in an integrated EP a significant increase in seismic recording production rates environment. Marcus has a Diploma degree in Geophysics (up to 400% increase), which would allow significant cost from the University of Munich. savings or gains in data quality. A potential problem is an enhanced noise level on the seismic records. Elaine Leith graduated with a BSc degree from the University of The slip-sweep method has been tested four times in several Newcastle upon Tyne and a PhD from prospects in Oman. The initial test data sets were recorded the University of Sheffield. She during a production survey, with all parameters identical to joined Shell in 1985 and worked as a the production survey (15 second sweep; 6 second listening Materials and Corrosion Engineer in time); this highlights any differences in the seismic data the UK, Netherlands and Oman. In quality. As current acquisition instruments cannot yet 1995 Elaine took up her current accommodate the slip-sweep method to its full extent, a position as a Production Engineer for modified version was employed with the slip-sweep Petroleum Development Oman’s simulated in the processing centre. deep high pressure Athel play. 166

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These tests have indicated that there are small differences area, where it hosts the recently discovered giant Hawiyah on loop-scale, with slip-sweep data being marginally nosier, gas-condensate field. The Jauf consists of shallow marine leading to the tentative conclusion that the slip-sweep sands which exhibit unusually high porosities considering method does not lead to significant deterioration of data- the burial depths. quality, nor does it lead to a different structural interpretation. Pre-Khuff hydrocarbon traps are found in simple four-way Following these encouraging results, recently a part of a 3- closures as well as more complex structural-stratigraphic D production survey was recorded in slip-sweep mode traps on the flanks of Hercynian structures. Trap formation employing two recording instruments by continuous and modification occurred in four main phases: the recording of a limited number of (up to 12) overlapping Carboniferous (Hercynian Orogeny); Early Triassic (Zagros sweeps. The results of this test will be presented and the Rifting); Late Cretaceous (First Alpine Orogeny); and quality compared with the remainder of the survey. Tertiary (Second Alpine Orogeny). Structures in the Ghawar area show differences in growth histories, which have Jan Wams graduated in 1975 from impacted the amount and type of hydrocarbons contained. the University of Delft in Medical Acoustics. He was drafted into the The primary source rock for pre-Khuff hydrocarbons are Dutch Army in early 1976 where he the basal “hot shales” of the Lower Silurian Qalibah researched laser- and night-vision Formation. Maturation modeling of these shales indicates equipment. Jan joined Shell in 1978 hydrocarbon generation began in the Middle Triassic (oil) and shortly after was transferred to and continues to the present (dry gas). the UK to take up a position in seismic data processing, followed by Lawrence E. Wender (see abstract "Geochemistry of postings in Thailand and Brunei as a Eastern Saudi Arabian Paleozoic Gas/Condensates" on page Seismic Interpreter. Jan was transferred back to Holland 80 for biography and photograph) in 1988 to head the Land Acquisition group, followed by a posting to Yemen as Chief Geophysicist. After a further Jeffrey W. Bryant joined Saudi year in Holland as an advisor on acquisition matters, he Aramco in 1990 as a Geologist joined PDO in 1993 to head the geophysical operations working frontier exploration of the department. northwestern region of Saudi Arabia. Since 1993 he has been exploring for Erik Kleiss (see abstract "From Noise Attenuation Towards Paleozoic deep gas reserves in the Signal Preservation" on page 128 for biography and Eastern Province of the Kingdom. photograph) Jeffrey has nearly 20 years of oil industry experience, including Alaska exploration and US Gulf Coast development with Exxon, and Gulf Coast of Mexico Pre-Khuff (Permian) Hydrocarbon exploration with Agip. Jeffrey holds a MSc in Geology from Geology of the Ghawar Area, the University of Arizona. Eastern Saudi Arabia Martin F. Dickens is a Geophysical Lawrence E. Wender, Jeffrey W. Bryant, Specialist with Saudi Aramco. He has Martin F. Dickens, Allen S. Neville, 20 years of international experience. and Abdulrahman M. Al-Moqbel Since 1993 he has been exploring for Saudi Aramco hydrocarbons in the Eastern province of Saudi Arabia. Martin holds a BSc Saudi Aramco is conducting an exploration program to in Geophysics from the University of discover additional non-associated gas reserves in the Southampton. Ghawar area. The program has successfully discovered significant sweet gas and condensate reserves in the pre- Khuff siliciclastics and has further increased our understanding of the Paleozoic petroleum system. AAPG Annual Meeting The Permian Unayzah Formation is the principal pre-Khuff 17-20 May, 1998 hydrocarbon reservoir in the southern Ghawar area, where it contains both oil and gas. The Unayzah consists of fluvial For more information please contact: AAPG Conventions Department to marginal marine sands. The Devonian Jauf Formation is Tel: (918) 560-2679; Fax: (918) 560-2684 the principal pre-Khuff reservoir in the northern Ghawar

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Allen S. Neville is a Geophysical 1,200 feet. Our tests showed that the source could generate Specialist with Saudi Aramco. He sharp P-wave first breaks which is preferable for accurate was previously with Gulf Oil tomography results. Corporation and has over 20 years of oil industry experience. Since We believe that the fundamental development of our joining Saudi Aramco in 1987, he has borehole source is almost complete. Future studies will been involved in the study and evaluate source characteristics such as radiation pattern, exploration of the Paleozoic in Saudi energy conversion efficiency, and its practicability. Arabia. Allen holds a MSc in Geology from Wright State Toshiyuki Yokota received BSc and University. MSc degrees in Mineral Science and Technology from Kyoto University in Abdulrahman M. Al-Moqbel is a 1989 and 1991, respectively. He Geophysicist with Saudi Aramco. He joined the Geological Survey of graduated in 1995 from the Japan in 1991 and was involved with University of Pacific (California) geothermal energy development. with a BSc in Geophysics. He has Toshiyuki joined Japan National Oil worked in the Geophysical Data Corporation in 1997. His current Processing Division and the Area interest is borehole seismology, Exploration Division. Abdulrahman especially cross-well tomography and seismic-while- has been involved in the study and drilling. exploration of the Paleozoic hydrocarbons in the Eastern Province of Saudi Arabia. He Shigeharu Mizohata received his is a member of the AAPG. BSc and MSc degrees in Geophysics from Kobe University. He worked with Japex Geoscience Institute Inc. Improvement on a Multi-Stage, in 1992, where he specialized in survey to detect active faults. He also Multi-Disk Type Borehole worked with VSP on crosswell project on geothermal area, which aimed to detect geothermal reservoir zone. Toshiyuki Yokota, Shigeharu Mizohata, Shigerharu joined Japan National Nobusuke Shimada, Yasutaka Shoji Oil Corporation in 1997 and is currently working for and Yoshiro Ishii development of borehole seismic source. Japan National Oil Corporation Nobusuke Shimada holds BSc and In 1991, OYO Corporation developed the first model of a MSc degrees in Geophysics from borehole seismic source (OWS: OYO Wappa Source) with Tohoku University. He joined Japan a spring accelerated, mass impact, single stage, fluid filled, National Oil Corporation (JNOC) in multi-disk design. Testing showed that this type of source 1985 and has been working on has several advantages such as good repeatability, easy project evaluation and geophysical operation and low electric power requirements. survey planning in Japan and overseas. Nobusuke is currently Japan National Oil Corporation and OYO Corporation have Assistant Director of Geophysics made recent design modifications to their borehole source Laboratory in Technical Research that will help assure its practicality for future oil field Center at JNOC. His current interests are reservoir geophysical surveys. Our tests show that a multi-stage, geophysics and reservoir characterization by integration multi-disk design effectively increases the source energy of multi-disciplinary data. output. The latest source now has six stages and ten disks in each stage. Our design also includes a unique method of Yasunori Shoji is currently an transmitting the energy from hammer to anvil, Engineer in the R&D Department of simultaneously impacting all six stages. OYO Corporation Instruments Division. He received his BSc and We performed a crosswell survey field test using our latest MSc degrees in Mining from Tohoku borehole source in a west Texas carbonate-reservoir oil field University. Yasunori joined OYO in 1996. The distance between the two wells was about Corporation in 1984 and has been working in developing instruments for both geophysical and geotechnical surveys. 168

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Yoshiro Ishii is currently the for biosteering control of the horizontal part of the well. Assistant General Manager of Japan This resulted in both reduced rig time and consultant time National Oil Corporation (JNOC), on well site. Middle East Representative Office in Abu Dhabi. He received his BSc from These, and techniques currently being investigated, provide Tokai University. He joined JNOC the tools and methods for onsite biosteering of horizontal in 1981 and has been working in new wells in homogeneous carbonates throughout the world. project evaluation and implementation of geophysical Charles R. (Bob) Young received BSc surveys around the world, including and MSc degrees in Geology from Oman, Jordan and Myanmar. Yoshiro was Head of Reservoir Wichita State University. He worked Geophysics Group at the Technological Research Center of as a Geologist and Biostratigrapher JNOC. with Texaco from 1969 to 1973, and as a Biostratigrapher/Senior Biostratigrapher with Atlantic Richfield Co. (ARCO) from 1973 to Biosteering Horizontal Wells in 1980. Bob is currently Senior Homogeneous Carbonates Using Biostratigrapher with Phillips Advanced High Resolution Petroleum Company. He is also a charter member of the Nannofossil Biostratigraphy International Nannoplankton Association.

Charles R. Young Phillips Petroleum Company The Stratigraphic Creation of Intrashelf Basins: Examples from Advanced High Resolution Nannoplankton Biostratigraphy techniques were used on archived (stored) North Sea well the Cenomanian/Turonian cores to subdivide both the Tertiary and Cretaceous chalk (Natih Formation) in North Oman reservoir intervals. The High Resolution Zones obtained were capable of resolving multiple sequences within the Frans S.P. van Buchem, Institut Français du Pétrole reservoir units. They were successfully used, on wellsite- Philippe Razin, University of Bordeaux, real time mode, to steer horizontally drilled wells within Alain Y. Huc, Institut Français du Pétrole, restricted target zones (e.g., upper third of reservoir interval). Bernard Pradier, Peter W. Homewood, Elf Each of the selected archived wells was the nearest cored and Heiko W. Oterdoom well to a horizontal well’s projected total depth. Petroleum Development Oman

The techniques provided high resolution nannoplankton Intra-shelf shallow basins are an essential part of carbonate zones with resolution finer than the conventional NN/NP, petroleum systems. The source rocks generally accumulate CN/CP, and KPN/Sissingh zones. The stratigraphic in the intra-shelf depression, while the reservoirs are formed resolution achieved is a fraction of a seismic wavelet. These during the time-equivalent aggradation and the subsequent techniques were used to subdivide: (1) the major Tertiary progradation of the carbonate platform. The Cenomanian/ reservoir unit (reworked Cretaceous Zone, Field Layer ED) Turonian carbonate system in Northern Oman shows twice of the Ekofisk field into three (four?) units; and (2) the this typical stratigraphic pattern (Natih E and Natih B Cretaceous reservoir (Tor Formation). The advanced members). techniques include: (1) population dynamics; (2) polar ordination; (3) morphometric analyses; and (4) synchronous This paper documents in detail the initiation and evolution variation of nannofossil assemblages and petrophysical of the Natih B intra-shelf depression, based on 16 detailed parameters. field sections and 10 wells covering an area of 120 by 60 kilometers (Jebel Akhdar, Adam Foothills, Natih field). A The use of archived cores and advanced nannofossil analytic high resolution cyclo-stratigraphic framework has been techniques to furnish a viable intra-reservoir level zonal constructed based on the bed-by-bed sedimentological scheme, as proven by the successful current horizontal well description in outcrop and in core, the specific gamma-ray drilling program, provided Phillips Petroleum with savings signature (wireline logs and outcrop natural gamma-ray of up to a million dollars per well. This was achieved by curves), and the measurements of carbonate and organic eliminating the need to core pilot hole, and run detailed matter distribution. The system evolves in the studied biostratigraphy on that core to obtain a viable zonal scheme transect from an initially flat topography with little lateral facies variations, into a platform to shallow basin topography

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during a 3rd-order transgressive phase. Facies consist alpine geology. He has been the Editor of Sedimentology initially of couplets of organic-rich/organic-poor limestone (1986-1990). Peter has a PhD from the University of beds, with a high abundance of oysters. Topography is Lausanne. created when carbonate productivity, and thus bed thickness, increases in the proximal position. The organic matter Heiko W. Oterdoom (see abstract "The Karim Oilplay: distribution varies considerably, but in a predictable pattern, Cambrian Alluvial-Lacustrine Deposits in South-Central in a vertical and lateral sense (0.03 to 14% Total Organic Oman" on page 97 for biography and photograph) Carbon Content (TOC), while its quality does not show any changes. In a cross-plot, carbonate and TOC show a perfect inverse linear relationship. This suggests a simple dilution relationship between the variable carbonate supply, and the Geochemical Evaluation of stable background sedimentation of marine organic matter the Djofra Saddle Area and clay. Linda M. Zeroual The geometrical evolution and sediment flux pattern of this Sonatrach intra-shelf basin are defined within the context of a high- resolution time framework. This provides a predictive model For more than forty years, the Djofra Basin, which includes for the source rock distribution, and its geometrical and exploration blocks 314 and 315, has not been extensively stratigraphic relationship to adjacent carbonate reservoir explored. The two Djofra exploration permits comprise an facies. area of 15,263 square kilometers. The lack of exploration activity can be assessed by the fact that only eight exploration Frans S.P. van Buchem see abstract "Geochemical wells were drilled between 1956 and 1978, all based on Simulation of Dolomitization in Platform Carbonate structural criteria. Reservoirs" on page 81 for biography and photograph) The primary target in this basin is a Lower Devonian Philippe Razin (see abstract "Sedimentology and Reservoir sandstone reservoir with fair to good porosity, ranging from Geometry of the Upper Permian Upper Gharif and Lower 8% to 30%. The reservoir permeability is poor, however, Khuff Formations in Interior Oman: Outcrop Study in the ranging from 0.1 to 0.7 mD, due probably to the presence Haushi Area" on page 82 for biography and photograph) of very fine-grained matrix and the abundance of carbonate and shaly cements. To date oil shows have been encountered Alain Y. Huc (see abstract "Distribution and Formation of in two wells: HMK-1 in block 314 and BEL-1 in block Pyrobitumen in Haima Reservoirs in North Oman" on page 350. 101 for biography and photograph) Despite the risk associated with this basin, exploration has Bernard Pradier is Organic resumed in these two blocks for several reasons: (1) the target Geochemist, and currently in charge reservoir is not very deep; (2) an excellent source rock of the Organic Petrology Laboratory consisting of the Silurian radioactive shale; and (3) the of Elf Exploration Production. He detection of seismic amplitude anomalies which are has a background in Uranium interpreted as Lower Devonian sand bars with stratigraphic Geochemistry (thesis, 1983), Organic trap potential. Petrology and Geochemistry (doctorate, 1988), and published The negative exploration results to date are interpreted to about thirty scientific papers. After be the result of mis-timing between hydrocarbon generation four years of fundamental research and migration, on the one hand, and the structural trap at CNRS, Bernard joined Elf in 1992. He manages research development. A comprehensive geochemical study, based projects concerned with hydrocarbon migration and organic on core cuttings and well data, is used to develop a model sedimentology, and is responsible for operational studies for the hydrocarbon habitat of the Djofra Basin. in petroleum system evaluation. Linda M. Zeroual graduated as Peter W. Homewood is Senior Geophysicist Engineer from the Scientific Adviser of Elf Aquitaine University of Algiers. She started Production. He has 23 years of working with Sonatrach in 1991. She professional experience, of which 14 then took up Geosciences studies at years were spent at the Universities the French Petroleum Institute of Zürich and Fribourg in between 1992 and 1993. Linda Switzerland, and 9 years in the rejoined Sonatrach and has been petroleum industry. His main fields working with the company since of interest are sedimentology, 1993. sedimentation and tectonics and 170

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