Petroleum Geochemistry and Exploration of Europe Geochemistry and Exploration of Europe

Edited by J. Brooks Exploration Division Britoil pie, Glasgow

1983

Published for The Geological Society by Blackwell Scientific Publications Oxford London Edinburgh Boston Melbourne Published by DISTRIBUTORS Blackwell Scientific Publications Editorial offices: USA Osney Mead, Oxford OX2 0EL Blackwell Mosby Book Distributors 8 John Street, London WC1N 2ES 11830 Westline Industrial Drive 9 Forrest Road, Edinburgh EH1 2QH St Louis, Missouri 63141 52 Beacon Street, Boston, Massachusetts 02108, USA Canada 99 Barry Street, Carlton, Victoria 3053, Australia Blackwell Mosby Book Distributors 120 Melford Drive, Scarborough First published 1983 Ontario M1B 2X4

1983 The Geological Society. Authorisation to Australia photocopy items for internal or personal use, or the Blackwell Scientific Book Distributors intemal or personal use of specific clients, is granted 31 Advantage Road, Highett by The Geological Society for libraries and other Victoria 3190 users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided British Library that the base fee of $02.00 per copy is paid directly Cataloguing in Publication Data to CCC, 21 Congress Street, Salem, MA 01970, Petroleum geochemistry and exploration of Europe.-- USA. 0305-8719/83 $02.00. (Special publications/GS, ISSN 0305-8719; no. 12) 1. Petroleum--Geology--Europe--Congresses Set by Preface Ltd, Salisbury I. Brooks, J. Printed at the Alden Press, Oxford 622'.1828'094 TN874.A1 and bound by Butler and Tanner Ltd, Frome and London. ISBN 0-632-01076-2 Contents

Page Preface vii

Introduction: BRooKs, J. ix

GEOLOGICAL AND GEOCHEMICAL STUDIES ON NW EUROPE CONTINENTAL SHELF WALMSLEY, P. J. The Role of the Department of Energy in Petroleum Exploration of the United Kingdom ...... 3 MAKOURINE, m. Gas Exploration and Reserves in Europe ...... 11 BARNARD, P. & COOPER, B. S. A Review of Geochemical Data Related to the Northwest European Gas Province ...... 19 GERVlRTZ, J. L., CAREY, B. D. Jr. & BLANCO, S. R. Surface Geochemical Exploration in the North Sea ...... 35 FABER, E. & STAHL, W. J. Analytical Procedure and Results of an Isotope Geochemical Surface Survey in an Area of the British North Sea ...... 51 S1GALOVE, J. Petroleum Offshore Sniffer Exploration* ...... 65 CANDY, G. J. Petroleum Exploration Onshore U.K.t ...... 67 BRENNAND, T. P. North Sea Petroleum Exploration* ...... 69 RONNEVIK, H., EGGEN, S. & VOLLSET, J. Exploration of ihe Norwegian Shelf ...... 71 MUDGE, D. C. & BLISS, G. M. Stratigraphy and Sedimentation of the Palaeocene Sands in the North Sea ...... 95 CURTIS, C. D. Geochemistry of Porosity Enhancement and Reduction in Clastic Sediments 113 IRWIN, H. & HURST, A. Applications of Geochemistry to Sandstone Reservoir Studies .... 127 PEARSON, M. J. & WATKINS, D. Organofacies and Early Maturation Effects in Upper Jurassic Sediments from the Inner Moray Firth Basin, North Sea ...... 147 PEARSON, M. J., WATKINS, D., PI'ITION, J-L., CASTON, D. & SMALL, J. S. Aspects of Burial Diagenesis, Organic Maturation and Palaeothermal History of an Area in the South Viking Graben, North Sea ...... 161 CORNFORD, C., MORROW, J. A., TURR1NGTON, A., MILES, J. A. & BROOKS, J. Some Geological Controls on Oil Composition in the U.K. North Sea ...... 175 FISHER, M. J. & MILES, JENNIFER, A. Types, Organic Maturation and Hydrocarbon Occurrences in the Moray Firth and South Viking Graben, North Sea Basin ...... 195 REITSEMA, R. H. Geochemistry of the North and South Brae Areas, North Sea ...... 203 GRIFFITH, A. E. The Search for Petroleum in Northern Ireland ...... 21'3 ROBERTS, D. G. Frontier Exploration in Western and Northwest Europet ...... 223

PETROLEUM EXPLORATION OF EUROPE MATrAVELLI, L., RICCHIUTIO, T., GRIGHANI, D. & SCHOELL, M. Origins of Natural Gas in the Po Valley, N. Italy* ...... 227 WHITICAR, M. & SCHOELL,M. Isotope Geochemistry of Natural Gases in Central Europe* .. 229 KUCKELKORN, K., WEHNER, H. & HUFNAGEL, H. Geochemical Observations of Oil Generation in the German Alps and their Foreland ...... 231 vi Contents

PETROLEUM GEOCHEMICAL PRINCIPLES AND TECHNIQUES WELTE, D. H., YUKLER, M. A., RADKE, M., LEYTHAEUSER, D., MANN, U. & RITI'ER, U. Organic Geochemistry and Basin Modelling--Important Tools in Petroleum Exploration ...... 237 McKENZIE, D. P. Basin Evolution and Hydrocarbon Generationt ...... 253 DURAND, B. & PARATrE, M. Oil Potential of Coals--A Geochemical Approach ...... 255 SCHENK, P. A., de LEEUW, J. W., VIETS, T. C. & HAVERKAMP, J. Pyrolysis- Mass Spectro- metry in Coal Chemistry: a study of the coalification of vitrinites and the typiciation of Australian Brown Coals ...... 267 BATI'EN, D. J. Identification of Amorphous Sedimentary Organic Matter by Transmitted Light Microscopy ...... 275 SMITH, P. M. R. Spectral Correlation of Spore Coloration Standards ...... 289 BUISKOOL TOXOPEUS, J. M. A. Selection Criteria for the Use of Vitrinite Reflectance as a Maturity Tool ...... 295 BARWlSE, A. J. G. Use of Porphyrins as a Maturity Parameter for Oils and Sediments ..... 309

GEOLOGICAL INFORMATION ON HYDROCARBON EXPLORATION ON THE U.K. CONTINENTAL SHELF Introduction: BAXTER, G.G. 319 McKAY, D. J. The Compilation of an Earth Science Bibliography for the North Sea and Adjacent Areas ...... 321 WIGLEY, P. Commercially Available Geological Databanks--U.K.C.S ...... 329 BROOKS, J. R. V. Geological Information from Hydrocarbon Exploration on the United Kingdom Continental Shelf ...... 343 CHEW, K. J. & STEPHENSON, H. EXPHST--A Program to Analyse the History of Explor- ation Success within a Basin or Country ...... 357 BAXTER, G. G. The Use of Computerised Information in Britoil, Exploration Division* 373

Subject Index ...... 375

* indicates an abstract only t indicates an extended abstract Preface

In editing this volume of over thirty papers from aegis of The Geological Society and the the Conference: Petroleum Geochemistry and University of Glasgow and thanks are due to Exploration of Europe the main aim has been Professor Bernard Leake and Ted Tremlett for speed, but concern for accuracy and style, I their assistance in the organisation of the hope has not been neglected. Attempts have Conference. Scientific support was given by been made to have a consistent format for each the Institute of Petroleum. Financial and scien- paper, but also to allow some freedom to indivi- tific support, a Conference reception and many dual authors. Some of the discussion on the other support facilities were provided by Britoil various papers is included in the volume. plc and all these are gratefully acknowledged. My task has been eased by the assistance Assistance must also be acknowledged from provided by Graham Baxter (Exploration Dick Fowle (LASMO), John Brooks (Depart- Data Services Group, Britoil plc) who under- ment of Energy), Bernard Leake (University took the task of co-ordinating the papers in the of Glasgow), Geoff Eglinton (University of section: Geological Information on Hydro- Bristol) and Graham Baxter (Britoil) who carbon Exploration on the UKCS, which was chaired the various sessions. organised by The Geological Society m The Conference was attended by over 350 Geological Information Group. Thanks are also delegates from U.K., Europe, North America due to colleagues, who helped out with ref- and some from even further afield. These ereeing some of the papers and special thanks delegates were mainly from oil companies, but are made to Chris Cornford who willingly consultant companies, research establishments, assisted in various ways in organising the government organisations and universities were Meeting, reading the manuscripts and even as all well represented. 'stand-in' projectionist at the Conference. It is hoped that the book will inform and The papers are assembled from two Con- assist workers in the oil industry and will be a ferences: Petroleum Geochemistry and Explo- useful reference for those working in petroleum ration of Europe and Geological Information exploration, not only in Europe but worldwide. on Hydrocarbon Exploration on the UKCS The volume will also be a relevant reference organised respectively by The Geological work for academic researchers and students in Society, Petroleum Geochemistry and Geologi- earth sciences wishing to understand and appre- cal Information Groups; held within the British ciate some of the recent advances in petroleum Isles Geological Congress at the University of exploration. I now leave the readers to explore Glasgow in September 1982. the various papers and trust they will gain some The compilation of the book would not, of the flavour of a very enjoyable few days at obviously have been possible without the con- the Conference. tributions of the various authors. I sincerely thank each author for their contribution and J. Brooks continued assistance in submitting and checking Glasgow, 1982 manuscripts. The meeting was held under the Introduction

Although the search for oil and gas in Europe, early as 1546 (Kent 1980). In Britain, seepage particularly in the North Sea, has been very oil was being used for medical purposes during successful, it has become progressively more the seventeenth century (Lees & Cox 1937). difficult and costly in recent years. The need Oil sands were mined for oil recovery during for continuing exploration success in finding the mid-1700s in the Pechelbronn area of the accumulations of hydrocarbons has created a Rhine graben and it is estimated that in the climate which favours the use of modern period up to 1860, more than 4000 metric tons scientific and technological methods and tech- of oil had been produced (Kent 1980). Britain, niques. Amongst these is petroleum geochemis- during the 1850s, saw the first use of seepage try. Applications of petroleum geochemistry oil recovered from a Derbyshire, U.K. coal (integrated with petroleum geology) in petro- mine. The first successful reported oil well was leum exploration has drastically changed in drilled in 1859 and discovered in the Wietze oil recent years from a post-mortem science to a field north of Hanover in northern Germany widely accepted exploration predictive tool. (Zeigler 1980). In 1918, following from the The oil industry, in its search for hydro- problems of importing crude oil during the carbons, has in recent years extended its 19 i 4" 18 First World War, the British Govern- exploration activity to take in the entire ment commissioned the first phase of U.K. continent of Europe, both on- and offshore deep exploration. The exploration programme basins. In addition to proving substantial oil and was based on analogy with the Pennsylvanian gas reserves, these studies have provided a vast Oil Fields and the objective was directed at amount of new geological and geochemical Carboniferous limestone accumulations in the information from many different areas of Southern Pennines and Scotland. A small oil Europe. These advances and applications are field was discovered at Hardstoft near reflected in this present volume. The pro- Chesterfield in 1922 and it was still producing ceedings of Petroleum Geochemistry and oil on a very small scale over fifty years later. Exploration of Europe contains papers by Exploration incentives lapsed during the 1920s experts in geology, geochemistry, sedimen- and the second phase of deep exploration did tology, data analysis, petroleum exploration not commence until the early 1930s when the and U.K. government policy that were anticlines in the Mesozoic basin of southern presented at an International Conference held England became the exploration targets. This within the British Isles Geological Congress at search for oil in southern England was the University of Glasgow in September 1982. encouraged by the occurrence of outcropping oil sands of Lower Cretaceous and Jurassic age (Lees & Tait 1946), together with probable Jurassic-aged source rocks at various locations Brief history of European petroleum from the Weald to Dorest (Gallois 1976; exploration Douglas & Williams 1981). Following from the small oil discovery at Hardstoft, exploration Exploration ofoil and gas has a long and varied activity later transferred back to the U.K. history in Europe, but it is only during the last East Midlands in the hope of finding hydro- few decades that geological understanding of carbon discoveries beneath unconformable North-west Europe and its extensive continental Mesozoic rocks (Kent 1980). The East shelves has been more fully understood. Since Midland operations met with mixed success and the late 1950s geological understanding of the the first commercial field was found at Eakring, North-west Europe offshore area has advanced Nottinghamshire in 1939, followed soon after- significantly mainly due to exploration and wards by three other discoveries. development activities by the oil and gas Exploration and some small commercial industry. production has continued onshore U.K. in the The oil industry has a long exploration Carboniferous (Southern Scotland; NW history in onshore parts of Europe. For England and East Midland), Permian (Eastern example, in North-west Germany, natural England), Triassic (Western England) and petroleum found at Hanover, Lower Saxony, Jurassic (Southern England) Formations. was already used for lubrication and lighting as During the late 1950s and early 1960s BP ix x Introduction drilled several wells in the Wessex Basin Dor- Extensive exploration for and development set U.K. and commercial oil was found in of oil and gas fields has provided a wealth of fractured Cornbrash in Kimmeridge No. 1 new data and during the last decade the geo- (1959) and in a thin fractured Inferior Ooolite logical understanding of Europe, particularly in Wareham No. 1 Well (1964). Further NW Europe, and its extensive continental evaluation of the Wessex Basin suggested that shelves has been more fully understood, mainly the Bridport Sands were probably a better due to the exploration and development reservoir target than the fractured poor activities by the oil and gas industry. The hydro- reservoir rocks believed to be producing in the carbon potential of the various regions of Kimmeridge No. 1 and Wareham No. 1 Wells Europe is by no means uniform and oil and gas (Colter & Harvard 1981). Wytch Farm No. 1 accumulations have been encountered in sedi- Well was spudded in 1973 and discovered light ments ranging in age from Pre-cambrian to oil in the Bridport sands. Subsequent ex- Tertiary. Hydrocarbon accumulations can be ploration and appraisal of the Wytch Farm correlated to specify depositional cycles and Field (Colter & Harvard 1981) has proved the distinct mega-tectonic units (Ziegler 1980, largest known onshore U.K. oil field with light 1981). A number of hydrocarbon provinces oil accumulation in both Bridport and Bunter have been defined based upon the age of their sand reservoirs. major hydrocarbon source rocks and their However, it was not until the discovery of principal reservoir formations, the type of the vast natural gas field at Groningen in the reservoir trap and also the regional oil and gas Netherlands in 1959, that extensive offshore assessment. Reviews of the evolution of major exploration activities commenced. After the oil and gas plays in Europe are given by Kent Second World War, Shell-Esso carried out (1975a, 1975b, 1980), Ziegler (1980, 1981), exploration over large areas of the Netherlands Burollett (1980), Naylor & Mounteney (1982) and drilled several tests in the Groningen region and Pergrum et al. (1982). Specific and in the northern part of the country. In 1959, detailed studies of regional geology and the Slochteren No. 1 Well was drilled through selected oil and gas fields are presented in two the Zechstein Formation and discovered that excellent Conference Volumes Petroleum the underlying basal Permian (Rotliegendes) Geology of the Continental Shelf of North- Sands were hundreds of feet thick and later West Europe (Eds. A. W. Woodland 1975 and shown to be more than 20 miles across, which L. V. Illing & G. D. Hobson 1981). A useful was entirely gas-bearing and very porous. This reference Geological Atlas of Western and unexpected discovery of recoverable gas rentral Europe, edited by P. A. Ziegler (1982) (5.69 x 10 TM m 3) made the field one of the has recently been published. Annual reviews of largest ever found. In addition to Groningen's European petroleum exploration activity are economic importance, the discovery also published in AAPG World Review (see Kat provided a new scale of reference for potential 1980, 1981). NW Europe offshore discoveries. Exploration- ists now begin to anticipate the possibility of large hydrocarbon accumulations rather than Development of petroleum geochemistry reservoirs measured in only tens of feet vertical thickness and acres in extent. The science of petroleum geochemistry is the Just over 18 years ago, in 1965, the first gas application of chemical principles to the study discovery in U.K. waters was made by BP at the of the origin, generation, migration, accumula- West Sole Field in the Southern North Sea tion and alteration of petroleum, and the use of Basin. This was followed immediately by the this knowledge in exploration and recovery of gas discovery of the Viking Field and, in rapid oil and gas (Hunt 1979). Although the concept succession by discovery of the Leman Bank, of petroleum originating from organic-rich Indefatigable and Hewett Fields in 1966. The and migrating into sands was first major turning point in the exploration for oil in observed by geologists in the late 1800s, these offshore NW Europe was the discovery of the early theories about the controlling principle of giant Ekofisk Field in the Norwegian sector of petroleum occurrences were often limited in the North Sea in December 1969. Following concept in that they mainly addressed the this major oil discovery, the North Sea has question of 'where' accumulations were located. proved to be one of the best areas for It has become clear during the last twenty petroleum exploration anywhere in the world years, that to be able to better answer the and a number of large oil fields have been question 'where', it is usually necessary to discovered. evaluate 'why, when and how much' petroleum Introduction xi was present in a basin and to understand and aware of the wide scope of different modern establish the generation, migration and geochemical analytical techniques and methods accumulation processes. This understanding is applicable to assist in petroleum exploration at essential if the oil industry is to improve its different phases from the initial frontier basin petroleum exploration success ratio. study through many different topics even to a Although hypotheses are periodically put better understanding of the origin and proper- forward for a non-biological, earth-mantle ties of reservoired heavy crude oil. origin of petroleum, the generally accepted Exploration drilling is becoming more ex- origin is from sediments rich in biologically pensive and less successful and petroleum derived organic matter found mostly on conti- geochemistry has now a recognised role to play nental shelfs derived initially in quiet water in exploration programmes. When a new ex- environments such as in lagoons, estuaries and ploration programme, especially offshore deep basins of restricted circulation (Demaison regions, is designed only a limited amount of & Moore 1980). Another environment favour- general geological information is normally able for accumulation of organic matter are available. Initial geochemical studies, include continental slopes (Dow 1978). the collection of outcrop samples (if possible) The formation of hydrocarbons is currently at the rim of basins being evaluated, followed understood as a complex series of geochemical by evaluation of the available information on processes within a source , by which the the filling of the basin (stratigraphic and facies original organic components of biological analysis) which may give preliminary indi- materials are converted to hydrocarbons and cations of potential source rocks and reservoirs. other organic compounds of varying degrees of Rapidly reducing oil and gas reserves in mature thermodynamic stability during sedimentation basins, together with increasingly remote and burial at elevated temperature and pressure locations and hostile environments of the in the subsurface. The term hydrocarbon source world's remaining unexplored sedimentary rock is probably best defined as a 'fine-grained basins is placing increasing economic and sediment that in its natural setting has or could technological needs on oil explorationists. generate and release significant amounts of oil These requirements together with an increasing and/or gas'. The classification of hydrocarbon geochemical understanding of the origin, source rocks (see Brooks & Fisher 1983) is generation, migration and accumulation of defined in terms of amount and type of organic petroleum has resulted in the increasing use of matter, its state or organic maturation (caused predictive models for locating new petroleum by temperatures in the range 50-180~ and by reserves. The scope of these models (see the nature and amount of hydrocarbons capable Yukler & Welte 1980; Waples 1983; of being produced (Brooks 1981). The burial of Yukler & Kokesh 1983) range from a sedimentary basin results in the contained qualitative and descriptive treatment of organic matter being subjected to increasingly limited exploration information to sophisti- higher temperature, which causes thermal and cated models which relate complex geological, chemical degradation of the insoluble organic geophysical and geochemical data into matter (kerogen) to form petroleum-like comprehensive and systematic basin analyses products. Primary migration of liquid and and prediction of petroleum accumulations. gaseous products out of the source rock and The determination of the most favourable subsequent secondary migration (via carrier petroleum exploration targets, depends upon horizons, faults etc.) into porous reservoir rocks the best use o; our geochemical knowledge of leads to formation of hydrocarbon accumu- source rocks, generation, migration and lations where further migration is halted by a accumulation, combined with the geology of the trap. basin. During the last decade petroleum geo- chemistry has become a useful and increasingly applied aid in petroluem exploration. Although many oil explorations are now more familiar with the basic concepts of petroleum Petroleum geochemistry and geochemistry, mainly due to the increase in the number of oil company research laboratories, exploration of Europe conference service companies and the publication of two The main emphasis in this book is on various excellent petroleum geochemistry text books by aspects of petroleum exploration in Europe with Tissot & Welte (1978) and Hunt (1979), the particular reference to petroleum geochemistry. oil industry is only very recently becoming The papers are divided into 4 sections. xii Introduction

Geological and geochemical studies of NW 'Petroleum Offshore Sniffer Exploration'. This Europe Continental Sheff paper reviewed the developments in electronic and analytical techniques which now permit The opening paper in the book 'The r01e of comprehensive geochemical analyses to be the Department of Energy in petroleum ex- carried out for trace amounts of dissolved ploration of the United Kingdom' by Peter hydrocarbons in water. Low level micro-seeps Walmsley (Department of Energy, London) (10-11g/litre) can be detected and used to assist describes the structure and function of the U.K. in evaluating hydrocarbon potential of a basin Department of Energy. There are two divisions presence/absence of structures and determine within the U.K. Department of Energy that whether the accumulation is likely to be gas have responsibility for petroleum exploration. or oil. These three papers on geochemical pros- Petroleum Production Division administers pecting provided much critical discussion and Licensing policy. All technical matters relating comment, some of which is recorded in the to exploration, development and safety are volume. handled by Petroleum Engineering Division. A series of papers on U.K. and North Sea The principal function of these divisions is to Exploration were presented. 'Petroleum advise Government Ministers on exploration exploration onshore U.K.' by Graham Candy policy and to carry out policy decisions. (SheI1-U.K.) reviewed the onshore exploration A review of 'Gas exploration and reserves in activity in the U.K. and discussed some of Europe' by A. Makourine (USSR: Member of Shell's exploration activities in the West the ECE Gas Committee-Geneva) presents Midlands. Much exploration and commercial data and summary of the official information activity has taken place in the UKCS and this supplied by European Governments to the was discussed by Tim Brennand (ShelI-UK) in participating ECE Group on natural gas his paper 'North Sea petroleum exploration'. resources and exploration for natural gas in This paper reviewed the history of North Sea Europe (including the USSR). The theme of exploration and the development of the main natural gas is continued in the next paper 'A hydrocarbon plays was integrated into a review of geochemical data related to the synopsis of the complex North Sea Basin southern North Sea gas province' by Patrick evolution, sedimentary fill characteristics, Barnard and Brian Cooper (RRI). This paper development of hydrocarbon traps and timing reviews the complex history of the Southem of hydrocarbon generation from relevant North Sea Basin, the occurrence, maturity and organic-rich source rocks. Similar theme and location of the gas source rocks timing, approach is used in 'Exploration of the composition and generation of the gas. Norwegian Shelf' by Hans ROnnevik, T. The next group of papers deals in detail with Vollset and S. Eggen (Norwegian Petroleum the somewhat contentious topic of geochemical Directorate) who report on exploration drilling surface prospecting. Joel Gervirtz, B. D. Carey on the Norwegian Shelf and the results of Jr and Steve Blanco (Tenneco Oil Company) successful exploration in the North Sea and in their paper 'Surface geochemical exploration north of 62 ~. Recent exploration work on three in the North Sea' propose that their studies areas north of 62 ~ (Haltenbanken, Traena- demonstrate that correct interpretation of baken and Tromsflaket) is given and geological geochemical data from gravity cores (and information shows the existence of two new integrated with geological and geophysical petroleum provinces and possibility for data) can be a great aid in the evaluation of the additional discoveries in other areas. A study hydrocarbon potential of prospects. Gaseous on 'Stratigraphy and sedimentation of the light hydrocarbons recovered from near-surface Palaeocene sands in the North Sea' is given by sediments from the North Sea Central and David Mudge and Graham Bliss (Britoil- Viking Grabens have been studied and are Glasgow). The Palaeocene of the North Sea reported in E. Faber and W. J. Stahl's paper Basin between 58 ~ and 62~ contains a number 'Analytical procedure and results of an isotope of important reservoir sands and this paper geochemical surface survey in an area of the reviews the regional tectonic setting and British North Sea'. This paper reports that deposition of sediments, which was dominated geochemical data from shallow sediments by subsidence in the Viking Graben and Witch reflects the underlying sub-surface petroleum Ground Graben areas and its importance in accumulations and allows the differentiation of developing the thickness and distribution of the dry areas from areas containing hydrocarbon Palaeocene sands. accumulations. Inter-Ocean Systems U.S.A. The diagenetic history of reservoir sands is carry out geochemical prospectivity using their discussed in'Geochemistry of porosity enhance- 'Sniffer Method' and Joel Sigalove reported on ment and reduction in clastic sediments' by Introduction xiii

Charles Curtis (University of Sheffield). The Northern Ireland and more widely in frontier diagenetic history is considered in three stages: areas of western and northwestern Europe. the first includes destruction of primary 'The search for petroleum in Northern Ireland' porosity by grain coatings and pore-filling by Tony Griffith (Geological Survey of Northern cements, followed by a period of leaching after Ireland) summarises the brief history of which the original trend of porosity reduction is exploration in Northern Ireland and reviews the re-established. The paper evaluates the scale of prospect that petroleum sourced by carbon- diagenetic modification at different stages and iferous sediments may be potential targets. A relates this to solute transport, solubilities and broad overview of 'Frontier exploration in chemical composition. The paper 'Applications 'Western and Northwest Europe' by David of geochemistry to sandstone reservoir studies' Roberts (BP-London) discusses the outer areas by Hilary Irwin and Andrew Hurst (Statoil- of the NW Europe continental shelf, their Norway) deals with the mineralogy, chemical hydrocarbon potential and divides the area into composition and physical properties of a number of geological provinces characterised reservoir sandstones and uses this information by differences in age, tectonic style and geolog- to establish the burial history of the reservoir ical history related to rifting and spreading of sediments and prediction of potential produc- the North Atlantic Ocean. tion problems. Geochemical parameters are used in reconstructing the burial history of a North Sea sandstone sequence. Petroleum exploration of Europe Two papers by David Watkins and Mike The first paper in this section 'Origins of Pearson (University of Aberdeen) on 'Organo- Natural Gas in the Po Valley, North Italy' is by facies and early maturation effects in Upper L. Mattavelli and co-workers (AGIP-Milan) Jurassic sediments from the Inner Moray Firth, and examines some of the problems which North Sea' and 'Aspects of burial diagenesis, occurred during their geochemical studies of organic maturation and palaeothermal history natural gases sampled from 48 gas fields in the of an area in the South Viking Graben, North Po Basin. Using stable carbon isotope data it is Sea' (with co-authors) deals with an oil-source possible to distinguish methane from three rock characterisation and organic maturation different sources in the Po Basin. The next study on a thick Kimmeridge Clay succession paper: 'Isotope geochemistry of natural gases from the inner part of the Moray Firth Basin in central Europe' by Michael Whiticar and and with a geochemical and mineralogy study Martin Schoell (Hanover) presented stable of a well in the South Viking Graben, North carbon and deuterium isotope data together Sea. The next paper in this section 'Kerogen- with light hydrocarbon gas content to charac- types, organic maturation and hydrocarbon terise and correlate the principle gas provinces occurrences in the Moray Firth and South of Central Europe. The final paper in this Viking Graben, North Sea Basin' by Michael section: 'Geochemical observations of oil Fisher and Jenny Miles (Britoil, Glasgow) generation in the German Alps and their fore- discusses kerogen palaeofacies and maturation land' by H. Wehner and co-workers (Hanover) history and relates these studies to the vari- reports on geochemical exploration studies used ations in hydrocarbon types found in these to follow migration paths from deeply buried areas of the North Sea. Further geochemical Tertiary and Mesozoic source rocks below the studies applied to North Sea exploration are Alpine overthrusts. given in 'Some geological controls on oil com- position in the U.K. North Sea' by Chris Cornford and co-workers (Britoil-Glasgow) Petroleum geochemical principles and and in 'Geochemistry of the North and South techniques Brae Areas, North Sea '~ by Bob Reitsema The opening paper of this section: 'Organic (Marathon Oil-Denver). The first paper uses geochemistry and basin modelling--important the North Sea dominant source rock tools in petroleum exploration' by Dietrich (Kimmeridge Clay Formation) as a model for Welte and colleagues (KFA-Julich) describes studying the geological controls on the oil modern applications of geochemistry to petro- properties of some hundred North Sea samples. leum exploration and highlights the changing The Marathon paper identified at least two role of petroleum geochemistry from a 'post- types of crude oil in the Brae Area, but uses mortem' science into a widely accepted predic- geochemical techniques to correlate both oils tive exploration tool. The paper also details the with a Kimmeridge source rock. use of petroleum geochemistry in predictive The next two papers, whilst studying the geological basin modelling. Dan MacKenzie UKCS, report recent exploration work in (Cambridge) discusses 'Organic reactions in xiv Introduction extentional basins' in the following paper and of biological marker studies as maturity uses these reactions to predict thermal and sub- parameters for oils and source rocks. In the sidence history of a stretched basin and to paper 'Porphyrins as maturity parameters for estimate organic geochemical reaction con- crude oils and sediments extracts', Tony stants, using observations on organic-rich shales Barwise (BP Research-Sunbury) describes the and siltstones from the North Sea and the origin and occurrence of porphyrins in oils and Pennonian Basin. rock extracts and the application of changes The following two papers deal with coal in molecular structure and distribution in studies. There has been long and extended determining thermal maturity of oil and discussion on oil potential of coals and sediments. Bernard Durand (IFP-France) in his paper 'Oil potential of coals--a geochemical Geological information on hydrocarbon approach' suggests that coals have a fair exploration on the U.K. Continental Shelf potential for oil (and gas) andthe poor The final section of the book deals with association between coal measures and oil 'Geological information on hydrocarbon accumulations is probably due to geological exploration on the U.K. continental shelf' rather than geochemical reasons. Studies on assembled from a Conference of the same name coal are continued and reported by Pieter and organised by the Geological Society's Schenck and co-workers (Delft-Netherlands) in Geological Information Group. The theme and the paper 'Pyrolysis-mass spectrometry in coal papers are briefly reviewed in the Introduction chemistry', where modern geochemical by Graham Baxter (Conference Organiser). techniques are applied to analyze a series of The first paper in this section 'The compil- vitrinite macerals and to relate these to their ation of an earth science bibliography for the biological precursors. North Sea and adjacent areas' by Duncan In recent years, transmitted light microscopy McKay (Britoil) reports on the bibliography of dispersed kerogen components (organic of data being compiled by Britoil's Explora- macerals) has become important, not only in tion Library and gives an overview of Earth studying organic maturation, but also in more Science literature. 'Commercially available fully assessing petroleum potential of sedimen- geological databanks--UKCS' by Peter Wigley tary basins. In 'Identification of amorphous (ERICO) reviews the major commercially sedimentary organic matter by transmitted light available systems which contain geological data microscopy' David Batten (University of from the UKCS. Information on the geological Aberdeen) describes the main components of and geophysical information from the UKCS sedimentary organic matter, palynofacies and available from the Department of Energy is methods to determine organic maturation levels described by John Brooks (Department of and their increasing applications in assessing Energy) in his paper 'Geological information source rock potential for hydrocarbons. Spore from hydrocarbon exploration on the UKCS'. coloration is an important parameter in Further details on commercially available infor- determining the organic maturation of mation is provided in 'EXPHST--a programme hydrocarbon source rocks and in 'Transmitted to analyse the history of exploration success light spectra of spore coloration standards as a within a basin or country' by Kenneth Chew maturation indicator', 'Trica Smith (University and Helen Stephenson (Petroconsultants) of Newcastle) reports a comparison between which reports on EXPHST programme written various oil industry spore coloration standards. to search for, extract and manipulate infor- Organic maturation of source rocks is also mation contained on commercial petroleum widely studied microscopically using reflected exploration data banks. In the final paper 'The light by measuring vitrinite reflectance and in use of computerized information in Britoil, the paper 'Selection criteria for the use of Exploration Division', Graham Baxter vitrinite reflectance as a maturity tool in (Britoil) summarises the work of Britoil's petroleum exploration' by T. Buiskool Geodata Group who provide six computerised Toxopeus (Shell-Rijswijk) discusses different information systems for oil explorationists types of vitrinite and reports on the importance within the Company. All the systems have been of selecting the highest reflecting vitrinite developed in response to specific requirements particles for measurement of organic matur- of geologists and geophysicists. ation and the implication to exploration. The book is completed with a Subject Index, In addition to microscopic studies to evaluate which aims to provide a usable reference to organic maturation of source rocks, there have the volume, but is not claimed to be too been recent major advances in the application extensive. Introduction xv

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J. BROOKS, Exploration Division, Britoil plc, 150 St. Vincent Street, Glasgow, 02 5L J, U.K.