Madbi Amran / Qishn Total Petroleum System of the Ma′Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen

Home , Abas (diatom), Aden, Ash Shihr District, Balhaf, Hajr District, Marib

2001 Rub' Al Khali Basin Yemen Volcanic 2019 Ghudun-Khasfeh Flank Province Basin (North) 2010 2101

SAUDI ARABIA Ma'Rib-Al Jabal Ras 1 Al-Saidah As'ad al-Kamil Jawf Basin Saif Bin Yazen Sunah Sunah Northeast Dostour Al-Wahdah Qarn Qaymah 1 Kamaran Raydan Meem Wadi Taribah 2004 Azal Balquis Al-Shura Hemiar North Jabal Samadan Kharir Suqatrah Masila-Jeza Basin Hemiar Al-Raja - Jannah Hemiar South Al-Tahreer Husn El Kradis 1 Hemiar West Shaharah Al Kharwah 1 Haru Sanaa Al-Wihdah Atuf Northwest Yah 1 Camaal North Camaal Nazaih Wadi Bana Tawila Ayad West Heijah Hays Structural Belt Lam 1 Mukalla Ma'een 1 Amal Ayad East 2009 Alif Mawza 1 Aser 1 High Jabal Nuqum Al Khair 1 Nakaa 1 Magraf 1 Y Jabal Habah Dhahab 1 emen V Jabal Barat 1 Al Nasr 1 Mintaq 1 Rajwan 1 Halewah-Sabatayn Mukalla

Sharmah Rift Basin olcanic Basin (South) Arabian Shield 2007

Red Sea Basin 2101

Taiz Shabwah YEMEN Basin 2002 2006

Mukalla Rift Basin Gulf of Aden 2005 0 100 KILOMETERS 2003 Aden 2071

EXPLANATION

Geologic province and code Madbi Amran/Qishn Total Petroleum System outline Gas field Assessment unit outline

Oil field Source rock outline Country boundary Location of thermal modeling (fig. 14) INDEX MAP City

U.S. Geological Survey Bulletin 2202-G

U.S. Department of the Interior U.S. Geological Survey Madbi Amran / Qishn Total Petroleum System of the Ma′Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen

By Thomas S. Ahlbrandt

U.S. Geological Survey Bulletin 2202-G

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Gale A. Norton, Secretary

U.S. Geological Survey Charles G. Groat, Director

This publication is only available online at: http://geology.cr.usgs.gov/pub/bulletins/b2202-g/

Version 1.0 2002

Any use of trade, product, or ﬁrm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government

Published in the Central Region, Denver, Colorado Manuscript approved for publication April 4, 2002 Graphics by author and Gayle M. Dumonceaux Photocomposition by Gayle M. Dumonceaux Edited by L.M. Carter Contents

Foreword ...... 1 Abstract ...... 1 Introduction...... 2 Acknowledgments ...... 2 Province Geology...... 2 Province Boundaries ...... 2 Geographic Setting ...... 2 Political and Exploration History ...... 2 Geologic Setting ...... 6 Total Petroleum System...... 7 Petroleum Occurrence...... 7 Source Rock and Oil ...... 15 Reservoir Rock...... 18 Seal Rock...... 21 Overburden Rock...... 21 Hypothetical Total Petroleum Systems ...... 21 Petroleum Assessment ...... 22 References Cited...... 27

Figures

1–3. Maps showing: 1. Geologic provinces, Madbi Amran/Qishn Total Petroleum System, assessment unit, and major petroleum basins in and adjacent to Yemen ...... 3 2. Location of cross sections, selected well locations, administrative provinces, and areas of dune sand of Yemen ...... 4 3. Structural elements including basins, highs, faults, and outcrop belts, and cross section locations...... 5 4. Cross section A–B across western and central portions of Yemen ...... 8 5. Cross section B–C across central and eastern Yemen...... 9 6–10. Charts showing lithostratigraphy, correlations, and spatial stratigraphic distributions for: 6. Phanerozoic rocks in Yemen ...... 10 7. Paleozoic rocks in Yemen and adjacent Saudi Arabia ...... 11 8. Jurassic rocks in Yemen ...... 12 9. Cretaceous rocks in Yemen ...... 13 10. Cenozoic rocks in Yemen, Oman, and Saudi Arabia...... 14 11. Schematic diagram of total petroleum systems in Ma′Rib–Al Jawf/ Shabwah and Masila-Jeza basins, Yemen...... 16

III 12. Tectono-stratigraphic, halokinetic, and petroleum generation history model of Ma′Rib–Al Jawf/Shabwah basin, western Yemen ...... 17 13. Tectono-stratigraphic and petroleum generation model of Masila-Jeza basin, eastern Yemen...... 18 14. Thermal maturation modeling for Ma′Rib–Al Jawf/Shabwah basin, western Yemen ...... 19 15. Petroleum system events chart for Madbi Amran/Qishn Total Petroleum System, Yemen ...... 20 16. Graph showing cumulative grown oil volumes versus discovery year for Yemen assessment unit ...... 23 17. Graph showing cumulative grown gas volumes versus discovery year for Yemen assessment unit ...... 24 18. Histogram showing estimated undiscovered oil field number and size distribution for Madbi Amran/Qishn Total Petroleum System, Yemen ...... 25 19. Histogram showing estimated undiscovered oil field number and size distribution for Madbi Amran/Qishn Total Petroleum System, Yemen ...... 26

IV Madbi Amran / Qishn Total Petroleum System of the Ma′Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen

By Thomas S. Ahlbrandt

Foreword A graphical depiction of the elements of a total petroleum system is provided in the form of an events chart that shows the times of (1) deposition of essential rock units; (2) trap forma This report, describing the petroleum resources of a total tion; (3) generation, migration, and accumulation of hydrocar petroleum system in Yemen, was prepared as part of the World bons; and (4) preservation of hydrocarbons. Energy Assessment Project of the U.S. Geological Survey. For A numeric code identifies each region, province, total this project, the world was divided into 8 regions and 937 geo petroleum system, and assessment unit; these codes are uniform logic provinces, which were then ranked according to the dis throughout the project and will identify the same type of entity covered oil and gas volumes within each (Klett and others, in any of the publications. The code is as follows: 1997). Of these, 76 “priority” provinces (exclusive of the U.S. and chosen for their high ranking) and 52 “boutique” provinces Example (exclusive of the U.S. and chosen for their anticipated petroleum Region, single digit 2 richness or special regional economic importance) were selected Province, three digits to the right of region code 2004 for appraisal of oil and gas resources. The petroleum geology of Total petroleum system, two digits to the right of these priority and boutique provinces is described in this series province code 200401 of reports. Assessment unit, two digits to the right of petroleum The purpose of the World Energy Project is to assess the system code 20040101 quantities of oil, gas, and natural gas liquids that have the poten The codes for the regions and provinces are listed in Klett and tial to be added to reserves within the next 30 years. These vol others (1997). umes either reside in undiscovered fields whose sizes exceed the Oil and gas reserves quoted in this report are derived from stated minimum-field-size cutoff value for the assessment unit Petroconsultants’ Petroleum Exploration and Production data- (variable, but must be at least 1 million barrels of oil equivalent) base (Petroconsultants, 1996) and other area reports from Petro or occur as reserve growth of fields already discovered. consultants, Inc., unless otherwise noted. The total petroleum system constitutes the basic geologic Figure(s) in this report that show boundaries of the total unit of the oil and gas assessment. The total petroleum system petroleum system(s), assessment units, and pods of active includes all genetically related petroleum that occurs in shows source rocks were compiled using geographic information sys and accumulations (discovered and undiscovered) that (1) has tem (GIS) software. Political boundaries and cartographic rep been generated by a pod or by closely related pods of mature resentations were taken, with permission, from Environmental source rock, and (2) exists within a limited mappable geologic Systems Research Institute’s ArcWorld 1:3 million digital cov space, along with the other essential mappable geologic ele erage (1992), have no political significance, and are displayed ments (reservoir, seal, and overburden rocks) that control the for general reference only. Oil and gas field centerpoints, shown fundamental processes of generation, expulsion, migration, in these figures, are reproduced, with permission, from Petro entrapment, and preservation of petroleum. The minimum consultants, 1996. petroleum system is that part of a total petroleum system encom passing discovered shows and accumulations along with the geologic space in which the various essential elements have been proved by these discoveries. Abstract An assessment unit is a mappable part of a total petroleum system in which discovered and undiscovered fields constitute a Since the first discovery of petroleum in Yemen in 1984, single, relatively homogeneous population such that the chosen several recent advances have been made in the understanding of methodology of resource assessment based on estimation of the that country’s geologic history and petroleum systems. The number and sizes of undiscovered fields is applicable. A total total petroleum resource endowment for the combined petroleum system may equate to a single assessment unit, or it petroleum provinces within Yemen, as estimated in the recent may be subdivided into two or more assessment units if each U.S. Geological Survey world assessment, ranks 51st in the unit is sufficiently homogeneous in terms of geology, explora world, exclusive of the United States, at 9.8 BBOE, which tion considerations, and risk to assess individually. includes cumulative production and remaining reserves, as well

1 as a mean estimate of undiscovered resources. Such undiscov Acknowledgments ered petroleum resources are about 2.7 billion barrels of oil, 17 trillion cubic feet (2.8 billion barrels of oil equivalent) of natural This paper benefited from discussions with Dr. David gas and 1 billion barrels of natural gas liquids. A single total Boote, Occidental Oil Company, and other members of the petroleum system, the Jurassic Madbi Amran/Qishn, dominates World Energy Consortium, an advisory group to the World petroleum generation and production; it was formed in response Energy Project. Reserves data are derived from Petroconsultants to a Late Jurassic rifting event related to the separation of the (1996) and oil data are derived from GeoMark (1998). The Oil Arabian Peninsula from the Gondwana supercontinent. This and Gas Journal and Dr. Istvan Csato of MOL Hungarian Oil rifting resulted in the development of two petroleum-bearing Company gave permission for use of selected figures in this sedimentary basins: (1) the western Ma’Rib–Al Jawf / Shabwah report that is much appreciated. Richard Pollastro and Timothy basin, and (2) the eastern Masila-Jeza basin. In both basins, Klett reviewed the manuscript and made many helpful petroleum source rocks of the Jurassic (Kimmeridgian) Madbi suggestions. Formation generated hydrocarbons during Late Cretaceous time that migrated, mostly vertically, into Jurassic and Cretaceous reservoirs. In the western Ma’Rib–Al Jawf / Shabwah basin, the petroleum system is largely confined to syn-rift deposits, with Province Geology reservoirs ranging from deep-water turbidites to continental clastics buried beneath a thick Upper Jurassic (Tithonian) salt. The salt initially deformed in Early Cretaceous time, and contin Province Boundaries ued halokinesis resulted in salt diapirism and associated salt withdrawal during extension. The eastern Masila-Jeza basin Yemen is located in the southwestern portion of the Ara contained similar early syn-rift deposits but received less clastic bian Peninsula, bordered by the Red Sea to the west, the Gulf of sediment during the Jurassic; however, no salt formed because Aden to the south, and the Arabian Sea to the east. It shares a the basin remained open to ocean circulation in the Late Juras common border with Oman on the east and a disputed border sic. Thus, Madbi Formation-sourced hydrocarbons migrated with Saudi Arabia on the north (fig. 2). Yemen is divided into 10 vertically into Lower Cretaceous estuarine, fluvial, and tidal geologic provinces by the USGS, 3 of which contain petroleum sandstones of the Qishn Formation and were trapped by overly (Klett and others, 1997). These three provinces are Ma’Rib–Al ing impermeable carbonates of the same formation. Both basins Jawf Basin (2004), Shabwah Basin (2006), and Masila-Jeza were formed by extensional forces during Jurassic rifting; how- Basin (2009) (fig. 1). One total petroleum system, the Madbi ever, another rifting event that formed the Red Sea and Gulf of Amran / Qishn, encompasses the hydrocarbon potential of Aden during Oligocene and Miocene time had a strong effect on Yemen and crosses these three petroleum province boundaries the eastern Masila-Jeza basin. Recurrent movement of basement (fig. 1). Subsequently, the geologic understanding of the area blocks, particularly during the Tertiary, rather than halokinesis, permitted combining the three provinces into two basins as was critical to the formation of traps. described in the total petroleum system section.

Introduction Geographic Setting This report describes the total petroleum system (TPS), the Yemen is bounded by 1,900 km (kilometers) of coastline of Jurassic Madbi Amran / Qishn of the Ma’Rib–Al Jawf Basin the Red Sea along its western border and the Gulf of Aden at its (2004), Shabwah Basin (2006), and Masila-Jeza Basin (2009) southern border. A narrow coastal plain adjacent to a mountain provinces (fig. 1). The estimated undiscovered resources of the ous Precambrian terrane to the west gives way to a dissected TPS are all contained within the country of Yemen. In terms of a upland desert plain to the east and merges into the great deserts political entity, Yemen is a relatively young country; and it is of the Rub’Al Khali farther to the north and east (figs. 2, 3). The also a recent petroleum-producing area, with the first petroleum climate ranges from hot and humid in the west to extraordinarily discovery of oil at Alif field in 1984 (fig. 1). Of the world’s 409 hot in the deserts to the northeast. geologic provinces that contain hydrocarbons, 3 such provinces The area of Yemen is 527,970 km2, about twice the size of are in Yemen and are combined into one total petroleum system the State of Wyoming. Yemen claims a 200-nautical mile (or to with a ranking of total petroleum endowment of 51st in the the edge of the continental shelf) exclusive economic zone. world. The total petroleum endowment of this TPS is an esti mated 9.8 BBOE (billion barrels of oil equivalent) (Ahlbrandt and others, 2000), and with a production of about 405,800 BOPD (barrels of oil per day) from this TPS (International Political and Exploration History Petroleum Encyclopedia, 2000), Yemen is now recognized as a significant petroleum-producing country. The geologic under- Politically, Yemen had been divided into two countries— standing of Yemen in the last two decades, particularly the last Northern Yemen (the Yemen Arab Republic, YAR), and South 10 years, has been substantially improved, causing an essentially Yemen (the former Aden Protectorate and later the People’s unexplored area to become an important petroleum-producing Democratic Republic of Yemen, PDRY)—until 1990 when area in a relatively short time. they were united to form the Republic of Yemen. North 2 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen est

E 2007

50° Hemiar North Hemiar W Hemiar Haru Hemiar South Nazaih 2009 Sharmah Rift Basin Sunah Sunah Northeast men. Gulf of Aden awila T 100 KILOMETERS aribah otal Petroleum System outline di T Heijah Wa Mukalla 2010 Camaal Atuf Northwest 2006 0 Basin Assessment unit outline Location of thermal modeling (fig. 14) Madbi Amran/Qishn T Source rock outline n Qaymah 1 Kharir Mintaq 1

Mukalla High Shabwah Qar Ghudun-Khasfeh Flank Province

TION Husn El Kradis 1 Camaal North

EXPLA Magraf 1 Masila-Jeza Basin est ahdah

Ayad East ARABIA ARABIA Al Kharwah 1 azen Ayad W Amal

Nakaa 1 Jabal Barat 1

Suqatrah 2005 Dostour Al-W Saif Bin Y SAUDI As'ad al-Kamil Al-Raja - Jannah Al-Saidah ihdah Jabal Ras 1 Shaharah Al-W Mukalla Rift Basin Halewah-Sabatayn 2019 Al Khair 1 Meem Dhahab 1 YEMEN Al-Shura 2101 Country boundary Geologic province and code Oil field City Gas field Al Nasr 1 Rub' Al Khali Basin Raydan Arabian Shield Balquis Aser 1 Rajwan 1 Kamaran Jabal Habah Mawza 1 Azal Aden

E 2101

45° Alif o lcanic Lam 1 Jabal Nuqum ahreer Ma'een 1 adi Bana 2002 W ah 1 Al-T Y 2004 emen V Sanaa Basin (North) Y aiz Jabal Samadan T Ma'Rib-Al Jawf Basin Hays Structural Belt

2001 olcanic Basin (South)

Yemen V Red Sea Basin INDEX MAP

Geologic provinces, Madbi Amran/Qishn Total Petroleum System, assessment unit, and major petroleum basins in adjacent to Ye

15 ° ° Figure 1.

Province Geology 3 ° ° ° ° 19 18 17 16

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4 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen 42°E 44°E 46°E 48°E 50°E 52°E

N a b i t (Najran T a Afif T h Sutu errane Boundaries Asir T Nabitah Orogenic Shahr-1 (An Nimas) Belt (Al Qarah) re errane) Block Al Khali Basin errane Rub' ? (Southern Flank)Hathouth-1 Rakhawt-1 18° Qinab-1 C Hathouth-2 Taur-2 Thamud-1 Taur-1 License Sanaa h Tarfayt-1 Basin Arc wt Sir ma dra Basin Ha Howarim-1 Al-Furt-1 Rayyan ? A Jiza - Qamar Basin Al-Fatk-1 Fartaq Wadi-Jeza-1 Khaywan-1 16° ? Jani-Mukalla HighThukmayn-1 SAY'UN (Marib-Shabwah-Hajar) Say' Beta-1 High un Rakhawt-1 Sab'atay - Ti Al Qarn-1 al Masilah Basin Alif-1 Sunah-1 hamah Kharwah-1 R Maljan-1 Basin E SANAA n

D B Sarar-1 yhut Basin Ash Masilah-1 Shuaib-1 AL HUDAYDAH ? Hufayr-1 Mukalla - Sa Basin ? S W. Siham Central MUKALLA E (Mahfid) Balhaf-1 Balhaf-2 A (J3) Balhaf 14° Uplift Basin J. Al Aswad TA'IZ High ? Ad Dali' Basin N DE OF A GULF Al Baydah Al Mahfid 0 100 200 KILOMETERS ADEN Abyan Islands Arc Gneiss Terrane Al-Mukalla 1.2-2.5 Ga 1.8-3.0 Ga Island Arc Abas Gneiss (older ages from (?Pan African) Basin (Pan-African Terrane Aden continental basement networking) 1.7-2.3 Ga beneath arc) 12°

EXPLANATION

Location of exploration wells Volcanic (Tertiary Yemen Volcanic Group) Subsurface Najd faults modified from Dyer and Husseini, 1991; Jurassic outcrop area (resting on basement except in northwest) Province Geology barbs show relative movement Basement outcrop area (Archean Late Proterozoic) Approximate limits of various Precambrian terranes Cretaceous on basement (Jurassic eroded/not deposited) Basin boundary Paleozoic outcrop area Anticline

5 Figure 3. Structural elements including basins, highs, faults, and outcrop belts, and cross section locations (red lines) (modified from Beydoun and others, 1998). Yemen (also called Sanaa) became independent of the Otto- Geologic Setting man Empire in 1918, and South Yemen became independent of a British protectorate in 1967. South Yemen (People’s Demo cratic Republic of Yemen, PDRY, or Aden) was a Marxist- Petroleum occurs in two rift basins in Yemen. In western dominated government until it merged with North Yemen to Yemen, petroleum is generated and produced in the Ma’Rib–Al form the Republic of Yemen. The unification of the republic Jawf / Shabwah basin, and in eastern Yemen in the Masila-Jeza and the technological revolution in petroleum exploration basin. These eastern and western basins are largely separated brought into the country in the 1980’s and 1990’s changed the by a structural high known as the Mukalla or Jahi-Mukalla High country dramatically in both political and economic terms. (figs. 1, 3). The western basin is known by a variety of names Currently, Yemen has a population of about 17.5 million, most such as Sabatayn, Marib-Shabwa-Hajar (Beydoun and others, of whom are Arabic and of the Muslim faith. 1998), and Marib-Shabwa basin (Brannin and others, 1999; Political turmoil has surrounded Yemen during its history Csato and others, 2001). Similarly, the eastern basin is also and continues to the present. During the time of separate North known as the Sayun al Masilah and Jiza-Qamar basin (Beydoun and South Yemen countries, 1967–1990, hostilities between the and others, 1998), Sayun basin, and Sir-Sayun basin (Csato and two countries resulted in the migration of hundreds of thou- others, 2001). These basins are part of a system of major rift sand of Yemenis from the south to the north. Following unifi basins, and various authors have used a variety of names for cation in 1990, a secessionist effort in southern Yemen in 1994 both the main basins and the sub-basins or grabens that occur failed, and the country remained a republic. It continues to be within them. The names used herein attempt to represent the an area in dispute particularly along its northern border with major petroleum basins or sub-basins within the three provinces Saudi Arabia. included in the Madbi Amran / Qishn Total Petroleum System. The complex political history of Yemen contributed to a Although the petroleum-bearing grabens are considered to general lack of petroleum exploration until the discovery of Alif be of Late Jurassic age, their origins can be traced back to Pre field in North Yemen in the Ma’Rib–Al Jawf / Shabwah basin in cambrian fault systems. During Precambrian time, the area 1984 (fig. 1) (Beydoun, 1966; Beydoun, 1989; Fairchild, 1992; underwent a major collision and terrane accretion from about Schlumberger, 1992; Petroconsultants, 1996; Bosence, 1997; 955 to 615 million years ago (Ma), when older magmatic Maycock, 1997). This successful exploration effort, in prov assemblages (≈2.95–2.55 billion years old) accreted with inces 2004 and 2006 (fig. 1), was led by Hunt Oil Company and younger magmatic, volcanic, and plutonic rocks (Husseini, its initial partners from Korea, who formed Yemen Hunt Oil 1989; Whitehouse and others, 1998). However, during the Company (YHOC). This company later merged with Exxon Infra-Cambrian (≈615 to 580 Ma), the southern Arabian penin Yemen to form Yemen Exploration and Producing Company. sula became extensional with intrusions of alkali-rich granites The initial oil discovery at Alif was followed by 11 other discov and volcanics as well as development of salt-filled extensional eries of both oil and gas (figs. 1, 2). basins. These rift basins were related to major wrench-fault sys A second petroleum basin area, here referred to as the tems such as the Najd, in the western Arabian Shield, which Masila-Jeza basin (province 2009), lies to the east of the consists of a series of northwest-southeast-trending left-lateral Mukalla High (fig. 1). Oil production was established there fault zones as much as 1,100 km long and 300 km wide (Hus in 1991 by a Canadian Oxy-led consortium (CanadianOXY/ seini and Husseini, 1990; Ellis and others, 1996). The presence CCC/Pecten/Occidental); the discovery of oil at Sunah field of 400 m of Infra-Cambrian syn-rift sediments and metasedi was rapidly followed by other discoveries at Heijah and ments in Yemen (Beydoun, 1997) and the known hydrocarbon Camaal and a dozen other fields (Mills, 1992; fig. 1). occurrence related to Infra-Cambrian salt basins in nearby Twenty exploration companies are now active in Yemen, Oman (Husseini and Husseini, 1990; Pollastro, 1999) led to mostly independents (International Petroleum Encyclopedia, early exploration efforts that focused on the potential of an 2000). Infra-Cambrian petroleum system. Currently, two state-owned oil refineries operate in Aden Exploration in the 1980’s, however, demonstrated that the with capacities of 170,000 BOPD and a 10,000 barrel per day Infra-Cambrian sediments were not petroleum bearing, but that topping plant in Marib. Two other refineries are in the plan petroleum potential existed in rocks, rifts, and structures of Late ning stage including increased capacity (75,000 BOPD) at Jurassic age. The orientation of the Jurassic rifts is likely inher Aden and a 120,000–200,000 BOPD refinery at Mukalla. A ited from the Infra-Cambrian Najd wrench faults, which were liquefied natural gas plant, to be built by Enron at Ras Omran reactivated during the Jurassic breakup of the Gondwana super- on the Arabian Sea, is designed to market gas to Asia from the continent. The petroleum-bearing grabens of Yemen are inter gas fields in the Ma’Rib-Al Jawf / Shabwah area of western preted to be the result of a failed arm of a triple junction that Yemen. A 400-km gas pipeline is planned for construction by occurred in Late Jurassic time (Kimmeridgian) (Greenwood and Enron from the western Yemen gas fields to Ras Omran. The others, 1980; Husseini, 1989; Jungwirth and As-Sururi, 1990; implementation of this 1993 plan to market LNG (liquid natu Schlumberger, 1992; Redfern and Jones, 1995, Csato and oth ral gas) has yet to be completed. As of 2000, oil reserves were ers, 2001). Kimmeridgian source rocks and Jurassic-age petro believed to be 4 BBO and gas reserves are given as 16.9 TCF leum systems are important worldwide, particularly within (trillion cubic feet) (International Petroleum Encyclopedia, extensional basins such as the North Sea (Ahlbrandt and others, 2000). 2000).

6 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen Following Jurassic rifting, sediments filled the resulting Madbi Formation; Csato and others, 2001), but the subsequent grabens from earliest Cretaceous (Berriasian) through Late Cre depositional and structural histories of the two basins are differ taceous time. A second phase of rifting and associated ent, as are the ages and quality of their reservoirs and seals. transpressional and transtensional structures were related to the As shown schematically in figure 11, the combined opening of the Red Sea and the Gulf of Aden during Oligocene Ma’Rib–Al Jawf and Shabwah basins (fig. 1) contain a petro and Miocene time (Beydoun, 1989; Haitham and Nanai, 1990; leum system that formed in the Late Jurassic. The basal petro Bott and others, 1992; Crossley and others, 1992; Huchon and leum source-rock interval in the syn-rift sequence is the Madbi others, 1992). During this rifting, sea-floor spreading separated Formation, which charges both clastic and carbonate Jurassic Arabia from Africa and the Arabian plate rotated in a counter- reservoirs in the Madbi Formation and Sabatayn Foramation of clockwise direction. Tertiary petroleum systems of the Red Sea the Amran Group; these formations are overlain by a salt seal of are largely within the rift sequence, whereas petroleum potential the Shabwah Member of the Sabatayn Formation (fig. 8). Res in the Gulf of Aden is thought to be largely in the pre-rift ervoirs in the Amran Group range from clastic turbidite sequence. The Gulf of Aden is cut by a series of northeast- sequences to strata of alluvial origin that were generally depos trending transform faults that reflect the oblique motion of the ited along the margins of the rift or as sediment that filled the Arabian plate from the Gulf of Aden; the Red Sea rift and basin progressively from the northwest to the southeast. Salt related structures formed mostly in response to plate movement diapirs create additional structures for traps in the western basin perpendicular to the ocean spreading center. In Yemen, the (figs. 11, 12); however, the salt seal is absent in the eastern southern portion of the Shabwah basin (known as the Balhaf Masila-Jeza basin, and hydrocarbons sourced from the Madbi basin) and much of the Masila-Jeza basin (specifically the migrated vertically into the Cretaceous Qishn Formation, where Hadramawt Arch) are also related to transtensional and reservoirs are largely contained within a clastic estuarine transpressional forces during the Tertiary rifting event (Bott and sequence (fig. 13). others, 1992; Richardson and others, 1994; Csato and others, The stratigraphic terminology for the Jurassic rocks of 2001) (fig. 3). Yemen is shown in figure 8 and for the Cretaceous in figure 9. The maximum extent of the Madbi Amran/Qishn TPS is mapped in figure 1 along with the pod of active source rocks (Ro>0.6 Total Petroleum System pct). The two basins in Yemen that contain the TPS, the Ma’Rib–Al Jawf / Shabwah basin in the west and the Masila- Jeza basin in the east, are separated by the Mukalla (or Jahi- The total petroleum system described in this report, the Mukalla) high (figs. 1, 2, 3, and 11), which is a northwest-south- Madbi/Amran/Qishn TPS, is entirely onshore. It is a Jurassic- east-oriented horst block that has undergone recurrent move sourced, and Jurassic- and Cretaceous-reservoired petroleum ment and may reflect the Infra-Cambrian Najd fault system. The system. Undiscovered oil and gas resources in this TPS were structural relations between the two basins and this positive fea quantitatively assessed. Two other potential total petroleum sys ture, which has been a structural high for most of the Mesozoic tems—the Cretaceous Nayfa (Naifa) petroleum system in east- history of Yemen, are not entirely resolved (Paul, 1990, Putnam ern Yemen and a possible Tertiary petroleum system in the Gulf and others, 1997; Beydoun and others, 1998; Csato and others, of Aden—were not assessed but are briefly discussed. 2001). Csato and others (2001) simplified the structural termi nology and discussed two basins separated by the Mukalla high. They interpreted the Mukalla high to be a persistent geologic Petroleum Occurrence feature reactivated in the Tertiary rifting but dividing major geo logic regimes; to the west extensional features formed, whereas Petroleum is currently produced in two main areas in to the east major inversion occurred. These authors believed Yemen; cross sections through the main petroleum-producing Hadramawt High or Arch (fig. 3) to be an uplift related to tec areas are located in figures 2 and 3, and shown in figures 4 and tonic rebound from the opening of the Gulf of Aden. This 5; structural elements are shown in figure 3. Although the strati- rebound was asymmetric; the southern flank tilted southward, graphic nomenclature is complex, the stratigraphic terminology resulting in high-angle tilted fault blocks in eastern Yemen (as used by Beydoun (1997) and Beydoun and others (1998) is shown in fig. 13). applied herein. Stratigraphic terminology and spatial relation- Jurassic salt halokinesis created additional structural traps ships of strata are shown for the Phanerozoic in figure 6, for the for hydrocarbon accumulations in the Ma’Rib–Al Jawf / Shab Paleozoic section in figure 7, the Jurassic section in figure 8, the wah basin. However, Jurassic salt was not deposited in the Cretaceous section in figure 9, and the Cenozoic in figure 10. In Masila-Jeza basin to the east, where structures are indicative of figure 6, the general Phanerozoic stratigraphic framework is inversion and uplift associated with transtensional and transpres shown (from west to east) across the Sab’atayn (Ma’Rib–Al sional forces and the more east-west orientation of Tertiary rift Jawf and Shabwah basins of this report, fig. 1), the Say’un ing (fig. 11). These Tertiary forces also modified the south end Masila basin, and the Jiza-Qamar basin. The latter basin, which of the Ma’Rib–Al Jawf / Shabwah basin creating the Balhaf is not productive, is included as a sub-basin within the Masila- basin (fig. 3), which has no recorded hydrocarbon production Jeza basin. The two petroleum-producing basins (Sab’atayn and (Crossley and others, 1992; Beydoun and others, 1998; Csato Sayun Masila) have a common source rock (the Kimmeridgian and others, 2001).

Total Petroleum System 7 B ar ' Jiza Nayfa Sa Sharwayn Mukalla Sufla Mb Umm er Radhuma Qishn 24` Harshiyat 13` o o 9 TD 2485 X 15 Y 4 Maljan-1 olcanics nd others, 1998). TD, Other igneous V Intrusive granite Coal Conglomerate 50 46` 03` o o 9 un - Masila Basin) ' TD 2917 X 15 Y 4 Sunah-1

Shuqra+Kuhlan

ar i

ferentiated) ferentiated) (Undif '

yfa yfa 90 d

a a

M Harshiyat-Mukalla Harshiyat-Mukalla Sa N Qishn 45` 15` o o with local structural highs 8 un Sector (Say ' Al Qarn-1 TD 3709 X 15 Y 4 Say 55 6 ` 49` 4 o o 7

TD 1907 X 15 Y 4 Q

ar ar

Thukmayn-1 '

n n

fa fa

? y

i i

y Shuqra+Kuhlan

120 ta

a a ' ad

Qishn Qishn

M Anhydrite Halite N a Dolomite Limestone Jahi- Mukalla High S 7 ` 44` (NC) 5 o o 7 atayn ' TD 3998 X 14 Y 4

Hufayr-1

Basin Hajar Sector Sab R R e

70 U Rus Rus 7 ` Sh K 18` 3 o

Balhaf Basin 7

erentiated) erentiated) f (Undif Gp wilah Ta TD 4096 X 14 Y 4 Balhaf-2 Aswad High 75 ? 2 ` 39` 0 o o 7 Kuhlan TD 2842 X 14 Y 4 Shuqra Ash Shuaib-1 Qishn 80 Nayfa 20` 50` o o 6 Siltstone Marl Sandstone Shale TD 2753 X 15 Y 4

Kharwah-1

n n y . )

B a s i n ta

Kuhlan

fer a

' ra ra

b q

120 u a

wilah Gp h

Madbi S S (Undif Recent/Q Ta 33` 48` o o a t y n ' 5 Alif-1 15 TD 4184 X Y 4 S a b (Marib - Shabwah Sector and Central high) 210 ? ? A–B across western and central portions of Yemen from Ma'Rib–Al Jawf/Shabwah basin into Masila-Jeza (modified Beydoun a ?

16`

01` o o

. . er f Amram Gp. Undif Gp. Amram 4 (platform) Sanaa Basin Khaywan-1 TD 1797 X 16 Y 4 TION Cross section j i d Quaternary Umm er Radhuma Fm. Rus Fm. Jiza Fm. Shuqra Fm. Kuhlan Fm. Oil production Gas and condensate Gas, noncommercial Latitude N. Longitude E. Exploration well test Wa Kuhlan Akbarah LEVEL '

(NC)

Scale 40 km m 400 EXPLANA J R K X Y SEA Q Distance in km Figure 4. total depth (in meters). Correlations queried where uncertain. Sh UeR A

8 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen B C

Distance in km 145 75 135 60 160 90 195 135 60 Masila Sector of Say'un - Masila Basin J i z a Q a m a r B a s i n Rub' Al Khali extending into Tertiary offshore Fartaq (Jiza Sector) (Qamar Sector) Hadramawt Arch Basin (S. Flank) Mukalla-Sayhut Basin High Scale 40 km Maljan-1 Beta -1 Tarfayt-1 Al-Furt -1 H

400 m Jiza a bshiyah Rus Thamud-1 UeR UeR Qinab-1 Wadi-Jeza-1 Mukalla L S SEA Al-Fatk-1 q Masilah-1 M arta LEVEL Sufla Mb Sarar-1 F at ? T R shiy u Har M Rus ? s ? h h r D J a a S ukalla F U iz q ra iy a m a a h Ha Q a rta T a Harsh m s S L e b m Qishn q a u bshiyah r R H h M d a a iy Sarar T d at h r R Shuqra D u m e a hiyat a J / mm TD 1753 ? U R M X 17o 11` ? (Undiff.) Q Haras u Mukall o is J k H a Y 51 04` TD 1800 Tillite h lla n n y X 17o 20` P / C b a S a o Qus ? a Ghaydah F rw Y 49 51` F H H a 'a ar a a UeR ishn ' a rta h TD 2485 r rta o Q rs S q Sa h X 15 24` N q Fartaq o a iy Y 49 13` y a ? / O fa t t M Q u is b EXPLANATION T TD 2750 a o h Lusb Mb D n D F X 16 02` Q Quaternary a Y 52o 19` ? rta q M Lr Cam Q q ta t UeR Umm er Radhuma Fm. u r is TD 2850 a k a h o a iy H. Hab n Sa'af Mb X 16 15` F Infra Habshiyah Fm. lla h S o a s n Y 51 47` r ' yfa h Camb. R a a Rus Fm. kalla N r a is u H a N J Jiza Fm. Q y Sa'ar M fa L Lusb Mb M Madbi a Sh /K i + S d 662 -27 Ma Sufla Mb b b Shuqra ? Infra -Cambrian Tuff TD 3443 i d 613 Ma M Maqrat Mb a Kuhlan TD 4502 Basement M X 16 o 23` TD 4211 T Tuhayr Mb at 3500 o Y 50o 19` X 18 01` D Duha Suhis Mb (projected) Y 49o 56` X 14 o 51` Sh Shuqra Fm. o TD 4300 Y 50 23` X 16o 18` K Kuhlan Fm. o TD 4404 Y 52 37`

Total Petroleum System J/ Jurassic/Triassic Basement Basement estimated at depth of at least 6500 below sea level P/C Permian/Carboniferous at 4420 (projected) X 15 o 01` Qus Qusaiba (Silurian) o Conglomerate Y 51 02` Sandstone Dolomite /O Cambro - Ordovician Paleozoic Siltstone Limestone Coal X Latitude N. Shale Anhydrite Other igneous Y Longitude E. Exploration well test Marl Volcanics Intrusive granite

Figure 5. Cross section B–C across central and eastern Yemen principally in Masila-Jeza basin (modified from Beydoun and others, 1998). TD, total depth (in meters). Correlations queried

9 where uncertain.

No Jurassic Jurassic No

o Group Mahra

o ? High Dhufar S E ° E ^ ° er 53 v ^ 17 o ? ? ? eature wt Arch: e ? ^ e men aqah Y ered o T v ^ Dabut ectiv ama ? ^ To group and basement f only co from the Cretaceous Hadr An eff Fartaq Shuqra ? Kuhlan ^ ? ° E Madbi Sharwayn 51 o 17°30' ^ ? ? T s, 1998). Jiza - Qamar Basin Habshiyah Sarar . ) ? ^ Ghaydah

^ No Jurassic Jurassic No o ? ^ o o Radhuma High Occur along some rifted basin margins ^ Fartaq o Qusaiba ^ er Jiza o o o o o ? Shihr Group Qishn ah o Mukalla yn ^ Rus a y l o ? o Umm ^ ? o o y ^ wa Kuhlan o o o Harshiyat Dibsiy o o o Sudair Ju

o Shuqra Sa'ar ^

Madbi o ^

o Nayfa wilah Group Group wilah Ta (South flank, between long 48° and 53° E.) Pre Jurassic profile, Rub' al Khali Basin, Overlain by thin Shuqra (Jur Khusa : ^ o o o o ^ Qalibah o o ° Qinab Group

^ On Basement Basement 20 On INSET

o o Say'un Masila Basin

^^ o

o Qishn Cretaceous N

° E ahi- Sa'ar - Nayfa or Jurassic No J High ^ ^ 48 o Mukalla o o o o ^ o Fanglomerates, breccias, turbidites. Other igneous Chert Kaninah ^ o ^ o o o o ^ o abens ^ r o ^ ^^^ ^ fshore area ^ o 30' N. 45' E. o o ^ ° ° o ulted g o o o 48 Ghabar Group Occurs in small fa in coastal areas centered on 14 ^

oo ?

o Mayfa'ah Aden Group

Sa'ar o

^ ^

Basin Hadramawt o

^ Nayfa

an Gp Gp an Sab'atayn Amr Coastal and of Gulf of oo ^ ^ o ? o Conglomerates Coal Intrusive granite o o o T ION ^ o x o ^ x Madbi o o ^ Sab'atayn x o ^ o o ^ oo o o ° E o o ^ Shuqra oo 45 o EXPLANA o ? o o o o o o f erentiated o o ^ o o o awilah Group o Kuhlan T o ^ Undif o o o o o ^ m en l c a n ic oo

lcanics o ^ Majzir

o ajid

o o ferentiated ferentiated Group Undif Ye o Vo o

Halite Shale stringers Vo W oo o

oo Amran Group Group Amran Akbarah o o o o o x o o o o o (Platform) o o x o o HIgh Plateau o ? ^ ? ? ^^ hamah Group ^ Ti Red Sea ^ ^ ° E ^ W 42 Marl Limestone Anhydrite Correlation or extent queried where uncertain. ort. Age . /Langian r e sian l anginian r o nian a r c./Hettang thonian

Messin./T Serrav Burd./Aquit. Chattian Rupelian Priobonian Barton./Lutetian Yp Thanetian Mont./Danian

Maastrichtian Campanian Santonian Coniacian Tu Cenomanian Albian Aptian Barremian Hauterivian Va Berriasian Ti Kimmeridgian Oxfordian Callovian Bath./Baj./Aalen To - CAMBRIAN U M L U L U M L U

L L Phanerozoic lithostratigraphy, correlations, and spatial stratigraphic distributions for Yemen (modified from Beydoun other Pliocene

Middle M M /Late U L/Early U/Late L/E Mioc. li. O oc. E Paleoc.

Period, Epoch, JURASSIC JURASSIC NEOGENE NEOGENE ACEOUS CRET TRIASSIC PERMIAN CARBONIFEROUS DEVONIAN SILURIAN ORDOVICIAN CAMBRIAN INFRA OGENE OGENE E L PA Sandstone Siltstone Shale

System, Series, Stage

Era Era MESOZOIC MESOZOIC LEOZOIC PA CENOZOIC CENOZOIC Figure 6. formation status only.

10 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen W E SW NE Period, Epoch, Age YEMEN SAUDI ARABIA (1) Subsurface Subsurface Outcrops Al Najran System, Series, Stage NW Yemen Jawf Rub' Al Khali Basin South Flank outcrops Rub' Al Khali - Central Arabia

TRIASSIC Sudair Fm Sudair Fm

U Khuff Fm o 'Akbarah o

L Unayzah PERMIAN Fm Fm o o o Juwayl Fm Juwayl U STEPHANIAN Mb o o o o o Juwayl Fm WESTPHALIAN o

M o NAMURIAN ? VISEAN ? Ur Khusayyayn L ? CARBONIFEROUS ? Mb Berwath TOURNAISIAN Khusayyayn Fm Fm FAMENNIAN o o Khusayyayn

U o oo FRASNIAN o o o o o o o Fm GIVETIAN Jubah Fm M EIFELIAN ? Ur Khusayyayn Jauf Fm

DEVONIAN EMSIAN Mb L

Fm Tawilah Fm GEDINNIAN o o o o o oo o o PRIDOLI Wajid o o o o o

U ? LUDLOW Fm ?

jid Sharawra Mb

M WENLOCK (Undifferentiated) Qalibah Fm o o Wa EXPLANATION

SILURIAN Qusaiba Mb ? Qusaiba Mb Qusaiba Mb L LLANDOVERY Sandstone o o Zarqa/Sarah ASHGIL Sanamah Qawara Mb Siltstone

U ? o Mb o oo CARADOC ? Shale Qasim Ra'an Mb LLANDEIL Fm Khafah Mb M ? Marl LLANVIRN o o o Hanadir Mb ? ? ? Limestone ORDOVICIAN ARENIG ?

L o ? o Dolomite TREMADOC o o o ? Dibsiyah Anhydrite U ? ? Dibsiyah Fm Saq Fm MERIONETH o o Mb o Fm Volcanics

Total Petroleum System o

M o o ST. DAVID'S o o o o o o o o o o o o o o o o o o o o Conglomerates ? o o o o o o o o o CAMBRIAN

L CAERFAI ? Coal ? ? ? Siq/Yatib Fms o o o o o o o Other igneous o o o GHABAR ? QINAB Group Chert o "J'BALAH Group" INFRA-CAMBRIAN GP o o o Coastal area o o o o o oo o o ooo o o oooo Crossbedding oo west of Mukalla o o o o o o o o o o o o o o o o

Figure 7. Paleozoic lithostratigraphy, correlations, and spatial stratigraphic distributions for Yemen and adjacent Saudi Arabia (modified from Beydoun and others, 1998). Correlation or 11 extent queried where uncertain. E (E) o Fm ? MADBI o Fm - QAMAR BASIN o SHUQRA ( W) JIZA o (SE) o Queried where uncertain. o o 1998). Fm o

BASIN Fm o o o o o o o o o

o o Mb Mb Rafad Rafad KUHLAN o o o o S Fm A SHUQRA ? o YF U Y'UN-MASILA MADBI NA SA o

Mb O

Maabir G R O U P P U O R G N A R M A o (W) o E ?

ACEOUS RESTS ON BASEMENT BASEMENT ON RESTS ACEOUS CRET JURASSIC: NO Mb Occur along some rifted basin margins A HIGH JAHI Nayfa Breccia

MUKALLA Conglomerates Fanglomerates, breccias, turbidites.

G R O U P P U O R G N A R M A T Mb Rafad o o o o o ? o o o (SE) TION Mb o E o Mbs Maqah o Mb o Maabir R o oo Mb o Mb Mb EXPLANA a d Layadim Shabwa Mb C Ay . Madbi Shales . Madbi Shales Lr Ur m AH-HAJAR) F olcanics Limestone Anhydrite Halite V YN BASIN A Y FA o T o Fm o o o o o NA Fm SHUQRA MADBI o

o Mb Mb o SAB'A o

o Raydan Mb o (MARIB-SHABW oo AND BORDERING OUTCROPS o Mb Lam o M b Mb Alif Mb h Meem o

Arwa

Safir Mbs Seen Mb Mb Mb

Ya Mb Haniyah (NW)

Hanb

N N Y

o (E) A

o Sandstone Siltstone Shale Marl

o Fm

tion tion i s n a

o TEAU Tr G R O U P P U O R G N A R

A M M A o

MADBI SABA'T o HIGH Gp o Fm WILAH PLA o KUHLAN OUTCROPS o TA ? (W) o W

AGE KIMMERIDGIAN KIMMERIDGIAN TITHONIAN TITHONIAN ANGIAN ACEOUS) Jurassic lithostratigraphy, correlations, and spatial stratigraphic distributions for Yemen (modified from Beydoun others, AGE ARCIAN THONIAN

ST BERRIASIAN

OXFORDIAN CALLOVIAN BA BAJOCIAN AALENIAN TO SINEMURIAN HETT

TRIASSIC (CRET

PLIENSBACHIAN EPOCH EPOCH MALM MALM DOGGER LIAS

Upper/Late Upper/Late Middle Lower/Early SERIES SERIES Figure 8.

12 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen STAGE WEST EAST AGE SERIES EPOCH 44°E 47 °E 50 °E 53 °E EOCENE Majzir PALEOCENE Fm ? ? UMM er RADHUMA Fm

MAASTRICHTIAN SHARWAYN Fm

TE CAMPANIAN ? o o DABUT Fm o MUKALLA Fm SANTONIAN o SENONIAN o ? o o o ? ? o

UPPER/LA CONIACIAN o TURONIAN o o o o o o Lusb o o ? Member o o o o o o o o o o o

CENOMANIAN Sufla Mb G R O U P o ? o o Maqrat Mb G R O U P o o Tuhayr Mb "MIDDLE" HARSHIYAT o ? Duha Suhis FARTAQ Fm ferentiated)

A H Member Rays Mb ? ALBIAN L oo I Fm M A H R A (Undif W o o o o o

T A ? o Qishn Carbonate Mb APTIAN o QISHN o EXPLANATION QISHN BERREMIAN o o Sandstone Clastics Mb Fm o o o QISHN Fm Y o o Shale o Sa'af ? o Marl HAUTERIVIAN Mb Limestone ? SA'AR ? ? Anhydrite Fm JAHI-MUKALLA LOWER/EARL VALANGINIAN Al Ghayl Mb High Volcanics SA'AR Fm no Sa'ar, Nayfa Qalana Mb o o

NEOCOMIAN Conglomerates or BERRIASIAN Jurassic Fm Samarma Mb Shale stringers

? o o o

NAYFA Fm o o JURASSIC NAYFA ooo Fm

Total Petroleum System (Tithonian)

Figure 9. Cretaceous lithostratigraphy, correlations, and spatial stratigraphic distributions for Yemen (modified from Beydoun and others, 1998). Queried where uncertain. 13 TION olcanics Queried where Marl Limestone Dolomite Anhydrite Halite V Shale stringers Conglomerates Sandstone Siltstone Shale Intrusive granite x x o oo x EXPLANA o o o o o o o o o o o o o o o o o o o o o o o o o o o A R) o o o o o o o o o o o o o o o o o o o o Aden o o o o o o o F m o o o o o o o of Fm Fm Fm Fm o Red o o o o o Fm o Damam d i m o o o Umm er o o o Rus Fm o Mughsayl Radhuma o o Ashawq o o o o o Adawib Fm Sharwayn Ay o o o Zulumah Fm o o o o Conglomerate Gulf o rom Beydoun and others, 1998). o o o o o oo

oo o o

o o o o OMAN (DHUF o o

GP GP WT HADRAMA

aqah Fm Fm aqah E T o o o o Fm o o o o oo o o o Fm o o ? o o Sharwayn

Sarar o Beds o Ghaydah Fm

o S o G P P G S H I H R R H I H S Habshiyah Formation o fshore Subsurface o o Hami Of

Shammar Mb o o Fm Buwaysh o o o o o o o Fm o o o Aden o Kaninah o

o o N

o Rus Fm o o of Fm Ambakhah o o Jiza o ransition o o T o o o o Jawl Mb o Fm Irqah o Umm er Radhuma o o o o

o o Gulf f.) o

Formation o o o Fuwwah Fm o o Fm Libakhah o o o o o o o Mayfa'ah Ain Ba Ma'bad Mb Onshore Exposure (Undif W I L AH GP

TA ?

G R O U P P U O R G C I N A C L O V N E M E Y o W M E N ? x E ? o Fm o ? o Majzir ? Y E Exposure Mb ? Lahimah Sea ? Abbas Fm Maqna Fm Salif Fm Red Ghawwas Mb ? Zaydiyah Fm Subsurface Kamaran Mb

? Not penetrated

TIHAMAH GROUP GROUP TIHAMAH ? ?

W Bald Bathan Fm Fm Bathan Bald o o o

o o

o o o o

Gp Gp o ? o Barqan Barqan o o o ?? Sea ? a jh Fm l canics Jizan ? Fm Lisan Vo Al W Red UDI ARABIA Kial Fm Ghawwas Fm Mansiyah Fm Barqan Fm J. Kibrit Fm Subsurface/Exposures SA S Cenozoic lithostratigraphy, correlations, and spatial stratigraphic distributions for Yemen, Oman, Saudi Arabia (modified f resian rtonian ichtian) OCENE CEOUS

Piacenzian Zanclian Messinian To Serravalina Langhian Burdigalian Aquitanian Chattian Rupelian Priabonian Bartonian Lutetian Yp Thanetian Danian

ies/Stage

U L U M L U L U M U L

System/ L

PLIOCENE PLIOCENE LEOCENE LEOCENE PA OLIGOCENE OLIGOCENE EOCENE

Ser MIOCENE

CRET (Maastr PLEIST

NEOGENE NEOGENE EOGENE L PA uncertain. Figure 10.

14 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen The Ma’Rib–Al Jawf / Shabwah basin in western Yemen skeletons estimated to be as much as 3 m long. The Shuqra was initiated during the Jurassic and was related to rifting of the source beds as referred to by Brannin and others (1999) are Arabian plate from the Gondwana supercontinent. Pre-rift sedi� likely the Lower Madbi Shale Member of Beydoun and others mentation is represented by mostly continental deposits of the (1998). Kuhlan Formation (fig. 8); this formation includes fluviatile and The pre-rift sequences are similar in both the eastern and arkosic redbeds that grade upward into a shallow-marine facies western Yemen basins, but the syn-rift fill in the east has consid� and represent the early transgressive phases of the Late Jurassic erably less sandstone (potential reservoirs). Structures in the seas. It is essentially absent of fossils; however, in the subsur� eastern basin are mostly related to rejuvenation of basin zones of face some palynomorphs have been recovered indicating a Mid� weakness in response to both Jurassic and Tertiary rifting forces, dle Jurassic (Bathonian to Early Callovian) age (Beydoun and rather than related to salt diapirism, as is evident in the western others, 1998). These continental rocks are overlain by shallow- basin. Both basins have multiple grabens and half-grabens that marine fossiliferous carbonates such as the Shuqra Formation of form stratigraphic traps, particularly along the margins of adja� the Amran Group (fig. 8). cent horsts. During the Late Jurassic, commencing in the Kimmerid� Only oil fields are found in eastern Yemen, reflecting a gian and continuing through the Tithonian, syn-rift sediments of lower thermal maturation of the Madbi shales relative to those in the Madbi Formation were deposited (Beydoun and others, the western basin. Thus, vertical migration of Madbi-sourced 1998). The Meem Member of that formation (fig. 8) consists of hydrocarbons charge mostly Jurassic reservoirs beneath the salt clastic turbidites and shales that are important source rock as seal in the west. In the eastern basin where no salt is present, the well as reservoirs in the western basin. The middle Maabir hydrocarbons migrate upward, are trapped in the Qishn Forma� Member is largely a carbonate sequence and a petroleum reser� tion’s fluviatile, estuarine, and tidal sandstone reservoirs, and are voir, and the upper Lam Member is mostly shaly strata. Clastic sealed by impermeable Qishn carbonates and shales (figs. 11 reservoirs also occur in the Madbi Formation and reflect deep- and 13). The Qishn deposits represent a transgressive marine marine sand deposition along the flanks of grabens or half-gra� sequence progressing from east to west across Yemen that bens. Simultaneously continental sediments filled the grabens grades laterally westward into clastics of the non-petroleum- from the north end of the western basin along rift margins. In bearing Tawilah Group (fig. 9). particular, these sediments formed the Safer, Alif, and Yan Members of the Amran Group (fig. 8). Apparently, ocean circu� lation in the western Yemen basin became restricted during the Source Rock and Oil Late Jurassic, and salts of the Shabwah Member of the Sabatayn Formation were deposited over the syn-rift sequence, thereby Within Yemen, geochemical data from 12 oils are reported providing a seal for the Jurassic petroleum system. in the GeoMark (1998) oil database. Seven oils are from Juras� The tectonic history of the Masila-Jeza basin was some- sic reservoirs in the Ma’Rib–Al Jawf / Shabwah basin; of these, what different from that of the Ma’Rib–Al Jawf / Shabwah six samples are from Alif, Azal, and Shabwah fields, and one basin. Whereas the basal source rocks of the Madbi Formation sample is from an oil seep. Three oils are from Jurassic and were deposited in a syn-rift setting, the overlying sequence was Cretaceous reservoirs in the Masila-Jeza basin (Sunah, Hemiar, relatively starved for clastic sediment input. A much later Creta� and Camaal fields; fig. 1), and two other samples are from Ter� ceous transgression of the Qishn Formation was thus required to tiary reservoirs in the Gulf of Aden. Although three groupings provide both reservoir and sealing carbonates, as illustrated in of oil were identified, oils from Jurassic reservoirs are dominant figures 11 and 13. In eastern Yemen, ocean circulation remained in both basins. The nine Jurassic-reservoired oils (seven from open during the Late Jurassic and Early Cretaceous, and open the west, two from the east) are genetically similar. API gravi� marine carbonates and clastics were deposited—but with no ties range from 29° to 35°, sulfur content from 0.09 to 0.59 per- Upper Jurassic salt seal (figs. 11, 13). Further, the eastern cent, and pristine / phytane ratios from 1.46 to 1.72. Biodegra� Yemen basin reflects east-west-oriented Tertiary rift forces, dation is suspected in the seep sample from the western basin compared to the western Yemen basin, which was dominantly due to its low API gravity of 14°, high sulfur content of 6.3 per- influenced by northwest-southeast-directed Jurassic-age forces, cent, and low pristine / phytane ratio of 0.3. The Cretaceous oil inherited from Infra-Cambrian faulting (fig. 13). sample from Hemiar field in the eastern basin is distinct from all The preferred pre-rift, syn-rift and post-rift sedimentary other oil samples, perhaps due to biodegradation; its gravity is sequences, as designated in this report, are consistent with those lower (22.2°), and sulfur content is higher (1.23 percent), but its shown by Csato and others (2001) (figs. 12, 13). Brannin and pristine / phytane ratio of 1.69 is within the range of the Jurassic others (1999) considered only the Madbi Formation and what samples. The Gulf of Aden Tertiary oils are also different, in they referred to as the Lam Formation to be syn-rift deposits. that they have high pristine / phytane ratios, 2.02 to 2.92, and (Note that Beydoun and others, 1998, considered the Lam to be reduced δC13values (<–24) as compared to all other samples a member of the Madbi Formation.) Stratigraphic divisions and whose δC13values range from –26 to –28.3. Some oil from the correlations advanced by Beydoun and others (1998) made a Gulf of Aden is anomalously high gravity, as much as 43°, as significant contribution toward clarifying the stratigraphic corre� noted by Beydoun (1989). These data indicate that the onshore lations in Yemen (figs. 6–10). The pre-rift Shuqra Formation, as oils in Mesozoic rocks dominantly belong to one genetic oil defined by Beydoun and others (1998), is a neritic limestone family, although biodegradation is suspected in the seep and with richly fossiliferous marls and does not contain potential Hemiar samples. The offshore, Gulf of Aden oils reservoired in source beds. Interestingly, the Shuqra contains crocodile Cenozoic rocks are from a different oil family. Total Petroleum System 15 s

r i

v SE

e ression

s i ansg

o ,

c ir

Qishn Carbonates

C Cretaceous tr u, Khar , Har

a-Saar Fm.

Na Hemiar Qamaal, and other fields Petroleum migration Oil reservoir Y'UN) BASIN MASILA-JEZA SA . ( rbidites olcanics Tu V actured Fr loses sealing capacity Maabir Mbr TION vy oil Hea EXPLANA HIGH oirs v ACEOUS rbidite CRET Tu reser Evaporites Siltstone and shale

MUKALLA

ad Member Member ad Raf .) . AH a Mbr yn Fm. Maabir Mbr , Meem, Amal, ydan, and other fields Sandstone Carbonates a Fm. a Fm. Alif Ra a dation yf r Saba'ta (Shabw Na Shuqr Meem Member Lam Member YN) BASIN WF/SHABW A T JA wilah Group Haniyah Member Ta (SAB'A a n Y a n o irs v , Alif ssic sandstone prog Schematic diagram of total petroleum systems in Ma’Rib–Al Jawf / Shabwah and Masila-Jeza basins, Yemen. MA'RIB-AL er A m r . r ra Madbi Fm.

(Saf Members)

Ju reser Ju

sag sag

NW fill

Rift Rift

ift ift ift ift e-r Pr ost-r P Figure 11.

16 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen SW Tertiary NE

0.5 Rifting

1.0 Rejuvenation of Jurassic

(sec) Faults 1.5 TWT Reactive to Active Diapirism 2.0 0 5 km

U. Cretaceous Tawilah Fm. 1 1 Naifa Hydrocarbon System 2 2 Madbi Hydrocarbon System

L. Cretaceous (Aptian-Albian) Qishn Fm.

L. Cretaceous (Valang.-Hauteri.) Post-Rift Naifa Fm. Passive Diapir Growths

Naifa Fm. Earliest L. Cretaceous (Berriaz.) Uplift of Northern Edge Reactive/Passive Initiation of Diapirs Rifting Tithonian Basinal Salt and Marginal Clastic Deposition

U. Jurassic (Kimmer.-Tithonian) Madbi Fm., Lam Member.

U. Jurassic (Kimmer.) Madbi Fm., Meem Mbr.

M. Jurassic Pre-Rift Marine Carb. Fluvial (Kohlan-Shuqra)

Figure 12. Tectono-stratigraphic, halokinetic, and petroleum generation history model of Ma’Rib–Al Jawf / Shabwah basin, western Yemen (with permission from Csato and others, 2001). TWT, two way time.

The source of hydrocarbons from the Madbi Amran / Qishn (Naifa) source rocks (Csato and others, 2001; ﬁg. 14). Csato TPS is believed to be Upper Jurassic Madbi (Kimmeridgian age) and others (2001) reported thermally mature Madbi Formation shales (ﬁgs. 14, 15). Petroleum-migration modeling in the in the Lam and Maabir-Meem members to contain source rocks deeper western basin demonstrates the effectiveness of Madbi with total organic carbon (TOC) ranging from 1.4 to 3.6 weight source rocks and the thermal immaturity of Tithonian Nayfa percent, hydrogen indices (HI) of 180–370 and TMAX values Total Petroleum System 17 N S Paleogene S.Hadramaut High Coastal Strip Gulf of Aden Half-Graben 1 inversion transtension tilting ocean floor

1 2

oceanic crust

Qishn Fm. uplift Naifa Fm. 2 Naifa Hydrocarbon System Madbi Fm. 1 Madbi Hydrocarbon System

South Arabian Peninsula Somalia

S.Hadramaut Complex ?

Cretaceous

South Arabian Peninsula Somalia S.Hadramaut Complex ?

U. Jurassic

M. Jurassic

Figure 13. Tectono-stratigraphic and petroleum generation model of Masila-Jeza basin, eastern Yemen (with permission from Csato and others, 2001). ranging from 224°C to 229˚C. Brannin and others (1999) In summary, the Kimmeridgian shales of the Madbi For reported TOC values of 2–5 percent and HI’s of 580 for the mation are probably the principal source rocks in both the east- Madbi Formation in the western Yemen basins, and reported as ern and western onshore basins of Yemen. One total petroleum much as 12 percent TOC (Rock Eval) in the pre-rift Shuqra For system was identified and assessed for both basins (fig. 1). mation with HI greater than 300. Thermal maturation of Madbi source rocks is believed to commence with oil generation at about 2,700 m (Csato and others, 2001). Thermal maturation Reservoir Rock modeling shows that with high heat flow, Madbi source rocks may have expelled oil from 135 to 90 Ma, and with low heat Reservoirs in the two basins are dependent primarily on the flow, from 85 to 50 Ma (Csato and others, 2001). Both models presence or absence of the Upper Jurassic (Tithonian) salt of the apply inasmuch as a variety of structural configurations and vari Sabatayn Formation (Shabwah Member) (fig. 8). In the western able heat flow exist within and among the basins. Essentially, oil Ma’Rib–Al Jawf / Shabwah basin, reservoirs beneath the salt generation commenced in the Late Cretaceous following deposi consist dominantly of clastics deposited either along the tion of significant post-rift clastics of the Tawilah Group (figs. 9, margins of the various grabens (Hayniyat and Rafad Members, 12, 13). fig. 8) or as turbidites (Meem and Lam Members) in the deeper 18 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen Vitrinite SW NE Reflectance Mintaq-1 Percent 0 (meters) 3000 6000 0.200–0.300 0 0.300–0.400 0.400–0.500 0.500–0.600 0.600–0.700 Tawilah 0.700–0.800 0.800–0.900 1000 Naifa- 0.900–1.000 Qishn 1.000–1.100 1.100–1.200 1.200–1.300 Madbi 1.300–1.400 1.400–1.500 2000 Kohlan 1.500–1.600 1.600–1.700

3000

5000 m

Figure 14. Thermal maturation modeling (PetroMod 4.2) for Ma’Rib–Al Jawf/Shabwah basin, western Yemen (with permission from Csato and others, 2001). Profile location shown in figure 1. Hydrocarbon generation commences at R0 = 0.7 percent vitrinite reflectance (green color) or higher.

portions of the grabens (figs. 8, 11). The upper part of the Juras grabens in the basins and their relations to salt dynamics (thin sic Amran Group and its coarser clastic units, Alif, Seen, Yah, over diapirs, thick in salt removal areas). The Jurassic syn-rift and Safir Members of the Sabatayn Formation, are the principal fill is as much as 4 km thick in the western basin, and individual reservoirs in the western basin (fig. 8). coarse clastic intervals along some rift margins are as much as The Madbi Amran / Qishn Total Petroleum System takes its 900 m thick (Brannin and others, 1999). Thus, some individual name from the Madbi Formation source rocks and the Amran reservoirs may be several hundred meters thick, but thin Formation (Jurassic Tithonian) carbonate and clastic reservoirs abruptly across intervening horsts (figs. 4, 5, 12, 13). Turbidite in the western basin beneath the salt and the Qishn Formation reservoirs and basin margin clastics are also important syn-rift (Cretaceous Berriasian) clastic reservoirs in the eastern basin reservoirs that intercept and trap hydrocarbons generated from where no salt is present (figs. 11, 13). Reservoirs in the western the deep marine source rocks of both the Meem and Lam Mem basin are relatively shallow, with depths ranging from 1,829 to bers of the Madbi Formation. Fractured rocks of the Maabir 2,286 m (from 6,000 to 7,500 ft) in the west (Petroconsultants, Member also have produced hydrocarbons, as have the pre-rift 1996). Initially, much of the production was established in successions of the Shuqra (carbonate) and Kuhlan (clastic) For Jurassic carbonate intervals; however, production from sand- mations. Reservoirs in these latter two formations are secondary stones became more dominant as the fields were more fully and generally of poorer quality relative to the Upper Jurassic developed. Porosities for the sandstones generally range from reservoirs (Brannin and others, 1999). 15 to 28 percent, with permeabilities ranging from 80 millidar In the Masila-Jeza basin, the Upper Jurassic salt is absent cies (mD) to 4 darcies. Most Jurassic sandstones have perme and the principal reservoir and trapping conditions exist in the abilities in the several hundred millidarcy range, and commonly transgressive Qishn Formation (fig. 9), which may be as much as in the one-half darcy range (Petroconsultants, 1996). Some res several hundred meters thick. The principal reservoirs occur ervoirs have lower porosities resulting from halite cement within a 75-m clastic interval of mixed sands and shales under- present in the pores, and some production problems are related lying a carbonate facies (Putnam and others, 1997) (fig. 11) that to salt precipitation and salt production in the western basin res forms a seal for Madbi Formation hydrocarbons migrating verti ervoirs (Schlumberger, 1992). cally as shown in figure 11. The eastern basin reservoirs are Reservoirs in the western basin were charged by vertically shallower than those in the western basin with producing depths migrating hydrocarbons that were trapped beneath a salt seal of about 1,524 m at Camaal, Heijar, Heimar, Haru, Suna, and formed by the Shabwah Member of the Sabatayn Formation (fig. Tawila fields (Petroconsultants, 1996; Putnam and others, 1997; 8). Halokinesis in the western basin commenced in Early Creta fig. 1). Reservoir quality for Qishn clastics is excellent. At ceous time and strongly influenced reservoir distribution there Camaal field, all Qishn reservoirs exceed 23 percent porosity (fig. 12). Thickness of these formations and members changes with permeabilities exceeding 1 darcy (Putnam and others, abruptly, depending upon their position relative to the horsts and 1997). Petroconsultants (1996) also reported high porosity and Total Petroleum System 19 ACCUMULATION

PETROLEUM

MIGRATION SYSTEM EVENTS

GEOLOGIC TIME SCALE

- ROCK UNIT RESERVOIR ROCK GENERATION

OVERBURDEN ROCK PRESERVATION PRESERVATION CRITICAL MOMENT TRAP FORMATION SOURCE ROCK SEAL ROCK 0 Plio HB Neogene Mio V R Gulf of Aden 24 Olig Rifting Paleogene Eoc UR 50 MK 65 Pal L TW 100 Cretaceous

E QN SB POST-RIFT AM 150 144 L SYN-RIFT M MD Jurassic SQ PRE-RIFT 200 E KH 206 L Tr iassic E M 250 248 L Permian E

290 L 300 Pennsylvanian M 323 E

L Sabatayn Fm. Amran Group Madbi Fm. Shuqra Fm. Kuhlan Fm. Ghabar Group Qinab Group Mississippian 350 E 363 L SB AM MD SQ KH GH QB Devonian M E TION 400 408 Silurian L TION NAMES 439 E 450 EXPLANA L FORMA Ordovician M E

500 olcanics awilah Group Habshiyah Fm. Rus Fm. Umm er Radhuma Fm. Mukalla Fm. T Qishn Fm. 510 L V M HB R UR MK TW QN V

Cambrian Petroleum system events chart for Madbi Amran/Qishn Total System, Yemen. 550 E GH 570 QB Precambrian

600 Figure 15.

20 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen permeability values for the eastern basin Qishn sandstone wells. infilling of the Tawilah Group, principally from the west to east In the eastern basin, tectonic rejuvenation related to Tertiary rift but including local sediment contributions from highs such as ing caused remigration and breaching of preexisting Jurassic the Mukalla high, account for most of the sedimentary overbur reservoirs. Extensive leakage must have occurred as heavy oil den (figs. 4, 5, 12). belts are known to occur on the margins of the Qishn reservoirs (David Boote, oral commun., 2000, illustrated in fig. 11). Hypothetical Total Petroleum Systems

Seal Rock A Silurian-sourced petroleum system may also exist, par ticularly in northeastern Yemen. As shown in the Paleozoic stratigraphic column for Yemen (fig. 7), the preservation of Sil Salt in the Shabwah Member (Tithonian) of the Sabatayn urian and Infra-Cambrian sediments in the Qinab-1 well (fig. 5), Formation forms the seal for the reservoirs in the Ma’Rib–Al particularly hydrocarbon source rocks, indicates the possibility Jawf / Shabwah basin (Seaborne, 1996). Salt sequences as much of a Paleozoic or perhaps Infra-Cambrian petroleum system as 30 m thick have been observed in outcrops, but in places there. The Silurian Qusaiba source rock that extends over much where the bases were not exposed (Beydoun and others, 1998). of Saudi Arabia was identified in outcrop in the Wajid Plateau of Brannin and others (1999) reported Sabatayn Formation salts as southwestern Saudi Arabia, where it is as much as 60 m thick. much as 1,500 m thick in the Amal field (fig. 1). The salt was Qusaiba strata may also have been encountered in Yemen in the mobilized shortly after deposition of the Nayfa (Naifa) Forma Qinab-1 well on the north flank of the Hadramawt Arch on the tion during Early Cretaceous time (fig. 12). Differential loading southern flank of the Rub’Al Khali basin (Stump and van der on the salt during sedimentation, as well as uplift of the Mukalla Eem, 1994; Beydoun and others, 1998) (fig. 5). Although the high, volcanism on the basin margins, and tilting of fault blocks potential may exist for a Silurian petroleum system in Yemen, associated with these activities, contributed to salt instability. the depth and thermal maturity of the Silurian Qusaiba shale for The thickness of overlying formations, particularly the Nayfa the southern Rub’ Al Khali basin indicate that it would be gas- and Qishn Formations, and Tawilah Group, is dependent on salt prone (Schenk and Pollastro, 2000). Assessment of the Paleo movement, thicker where salt withdrew and thinner over diapirs zoic potential for the Rub’Al Khali portion of Yemen was (fig. 12). included in the Qusaiba Silurian Total Petroleum System, and In the Masila-Jeza basin, the salt is absent; thus, hydrocar allocation of resources was made to Yemen (USGS, 2000). bons generated from the Jurassic rifts migrate upward until they Immature source-rock intervals were identified in the are trapped generally within the Qishn sandstone reservoirs Jurassic: Sabatayn Formation (Tithonian); the Cretaceous Nayfa beneath the Qishn carbonate unit (figs. 11, 13). The presence of (also spelled Naifa, Berriasian), Saar ( Berriasian), Qishn degraded oils and heavy oils in some of these fields indicates (Hauterivian-Barremian), Harshiyat (Albian-Aptian), Mukalla that the seal in the eastern basin is less effective than the salt seal (Coniacian to Maastrichtian); and the Paleocene and Eocene to the west. Umm er Radhuma and Jeza Formations (Barnard and others; 1992; Bott and others, 1992; Csato and others, 2001). Another Tertiary total petroleum system probably exists Overburden Rock basinward (coastal and offshore areas) of the onshore Masila- Jeza basin (fig. 13). Hydrocarbons have been produced from Overburden rock includes the Cretaceous and younger Tertiary strata in several wells, and are genetically distinct, with post-rift fill. The Early Cretaceous Nayfa (Naifa) Formation is different gravity (both much higher and much lower) and higher thus considered post-rift and the Upper Jurassic salt is consid sulfur content than the Jurassic-sourced hydrocarbons. This ered syn-rift. This interpretation, as shown in figures 11 and 13, potential Tertiary TPS is evidenced by hydrocarbon shows in is consistent with that of Csato and others (2001). Brannin and wells drilled offshore that tested oil from Oligocene and others (1999) discussed two post-rift sequences: (1) Ayad, Miocene reservoirs (Richardson and others, 1994). The Sabatayn, and Naifa Formations, and (2) the Qishn Formation Sharmah-1 well in the Gulf of Aden (fig. 2), for example, pro and Tawilah Group. In this report, the latter is considered to be duced 3,700 BOPD of 43° API gravity oil on a test from a mid post-rift and the former as syn-rift deposition. In areas where dle Eocene carbonate (Beydoun, 1989). To 2001, however, Tertiary rifting is predominant, as much as 4.5 km of post-rift commercial production has not been established in the Gulf of overburden was deposited, such as in the Balhaf basin on the Aden from this hypothetical TPS. The high heat flow, as much south end of the Ma’Rib-Al Jawf / Shabwah basin (fig. 3). Clas as 26.5°C/100 m near the spreading center, indicates the exist tics of the Tawilah Group are the dominant sediments in these ence of an oil window starting at depths from 2,438 to 2,743 m Tertiary rift grabens (figs. 4, 5), and more typical overburden (from 8,000 to 9,000 ft) in the offshore of the Red Sea and Gulf depths are in the 1–2 km range in the western basin and 2–3 km of Aden (Beydoun, 1989; Barnard and others, 1992). In the in the eastern basin (figs. 4, 5, 12, 13). The earliest post-rift sed onshore area, oil-prone source rocks of Tertiary age were iments are the transgressive Nayfa Formation clastics and car identified in the Masilah-1 well (figs. 3, 5), but they showed only bonates that prograded generally from west to east, thinning to modest organic richness and fair pyrolysis yields, and were the west but crossing both basins. The clastic progradation and thermally immature (Barnard and others, 1992).

Total Petroleum System 21 Petroleum Assessment with 4.3 billion barrels of oil equivalent (BBOE), exclusive of U.S. provinces. When undiscovered potential is added to known reserves, the total petroleum endowment for the Madbi Amran / Qishn TPS rises to 9.8 BBOE, which then ranks Production was first established in Yemen in 1984 but was Yemen 51st for potential of petroleum resources, exclusive of not included in a previous assessment by the USGS (Masters and the U.S. The estimated number and sizes of undiscovered oil others, 1994). In the present assessment, only one assessment and gas fields for the Ma’Rib–Al Jawf / Shabwah / Masila AU unit (AU), the Ma’Rib–Al Jawf / Shabwah / Masila AU (20040101) are shown in figures 18 and 19. (20040101), is identified within the Madbi Amran / Qishn TPS Although Yemen is a relatively immature petroleum- (200401) (fig. 1). Because the country and its petroleum prov producing country from an exploration standpoint, sizes of inces do not have a long discovery history, field growth is discovered fields already show significant decline. However, believed to be especially important for assessing future potential. the undiscovered potential, at the mean, was viewed to be larger Known oil reserves as of 1/1/96 were about 2 billion barrels of than what has been discovered to time of this report. The poten oil (BBO) (USGS, 2000). Known gas reserves as of 1/1/96 were tial resides principally in combination structural/stratigraphic about 11 trillion cubic feet of gas (TCF). The potential size of traps related to the complex interplay of rift-filling sequences discovered fields using a field growth algorithm is shown in fig within multiple grabens, half-grabens, and horsts. In the ures 16 and 17 as reported in USGS World Petroleum Assess Ma’Rib–Al Jawf / Shabwah basin, petroleum traps associated ment 2000 (USGS, 2000). with salt tectonics provide many trapping styles. Intra-salt and The undiscovered resources estimated in this assessment supra-salt reservoirs are considered viable plays and are being are reported as probability distributions. It is therefore conve actively explored. In the Masila-Jeza basin, rejuvenation of nient to describe the results in terms of mean values and F95 basement extensional fault blocks, as well as some transpres and F5 probability levels. The mean estimate of undiscovered sional features with associated stratigraphic/structural traps, will oil is 2.7 BBO with a F95–F5 range from 1.0 to 4.7 BBO. likely result in future discoveries. The mean estimate of undiscovered natural gas is 17.0 TCF The potential for undiscovered oil and gas resources in with a F95–F5 range of 6.5 to 30.0 TCF. The mean estimate the Mesozoic Nayfa (Naifa) petroleum system was not of undiscovered natural gas liquids (NGL) is 0.9 billion bar assessed, but the limited areal extent of potential source rocks rels NGL (BBNGL) with a F95–F5 range of 0.4 to 2.2 and their shallow depth of burial and concomitant immaturity BBNGL. For known petroleum resource volumes, the (Csato and others, 2001) make its hydrocarbon potential Ma’Rib–Al Jawf basin province (province 2004) ranks 61st relatively limited.

22 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen

23 23 Assessment Petroleum

Figure 16. CUM. GROWN OIL VOLUME (MMBO) 4,000 1,000 1,500 2,000 2,500 3,000 3,500 500 Cumulative grown oilvolumesversusdiscoveryyear forYemenassessmentunit(from USGS,2000). 0 1980 Ma'Rib– 1982 A l J a 1984 wf/Shabwah/Masila 1986 FIELD DISCOVERY YEAR 1988 1990 , AssessmentUnit20040101 1992 1994 1996 1998 2000 2000 1998 1996 1994 1992 1990 1988 FIELD DISCOVERY YEAR 1986 wf/Shabwah/Masila , Assessment Unit 20040101 a 1984 J l 1982 M a'Rib– A 1980 0 Cumulative grown gas volumes versus discovery year for Yemen assessment unit (from USGS, 2000).

5,000

25,000 20,000 15,000 10,000 CUM. GROWN GAS VOLUME (BCFG) VOLUME GAS GROWN CUM. Figure 17.

24 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen Ma'Rib–Al Jawf/Shabwah/ Masila, Assessment Unit 20040101 Undiscovered Field-Size Distribution 25

Minimum field size: 5 MMBO

20 Mean number of undiscovered fields: 71.5

5 UNDISCOVERED OIL FIELDS (No.) UNDISCOVERED OIL

0 4-<8 8-<16 16-<32 32-<64 64-<128 128-<256 256-<512 512- 1024- 2048- Petroleum <1024 <2048 <4096 OIL FIELD SIZE (MMBO) Assessment

Figure 18. Estimated undiscovered oil field number and size distribution for Madbi Amran/Qishn Total Petroleum System, Yemen (from USGS, 2000). 25 12288- <24576 6144- <12288 000). 3072- <6144 1536- <3072 Minimum field size: 30 BCFG Mean number of undiscovered fields: 35 768- <1536 384-<768 GAS FIELD SIZE (BCFG) 192-<384 Undiscovered Field-Size Distribution 96-<192 48-<96 Ma'Rib–Al Jawf/Shabwah/ Masila, Assessment Unit 20040101 24-<48 Estimated undiscovered gas field number and size distribution for Madbi Amran/Qishn Total Petroleum System, Yemen (from USGS, 2

8 6 4 2 0

14 12 10 UNDISCOVERED GAS FIELDS (No.) (No.) FIELDS GAS UNDISCOVERED Figure 19.

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28 Total Petroleum System, Ma’ Rib–Al Jawf / Shabwah, and Masila-Jeza Basins, Yemen