Seals, Traps, and the Petroleum System

Transcription

1

2 Seals, Traps, and the Petroleum System Edited by R.C. Surdam Institute for Energy Research University of Wyoming Laramie, Wyoming AAPG Memoir 67 Published by The American Association of Petroleum Geologists Tulsa, Oklahoma, U.S.A

3 Copyright 1997 The American Association of Petroleum Geologists All Rights Reserved Published 1997 Printed and bound in the United States of America ISBN : Seals, traps, and the petroleum system/ edited by R.C. Surdam. p. em. -- (AAPG memoir: 67) Includes bibliographical references (p. ) and index. ISBN (alk. paper) 1. Traps (Petroleum geology ) I. Surdam, Ronald C. II. Series. TN S '8--dc CIP AAPG grants permission for a single photocopy of an item from this publication for personal use. Authorization for additional copies of items from this publication for personal or internal use is granted by AAPG provided that the base fee of $3.00 per copy is paid directly to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, Massachusetts Fees are subject to change. Any form of electronic or digital scanning or other digital transformation of portions of this publication into computer-readable and/ or transmittable form for personal or corporate use requires special permission from, and is subject to fee charges by, the AAPG. Association Editor: Kevin T. Biddle Science Director: Richard Steinmetz Publications Manager: Kenneth M. Wolgemuth Special Projects Editor: Anne H. Thomas Production: Custom Editorial Productions, Inc., Cincinnati, Ohio THE AMERICAN ASSOCIATION OF PETROLEUM GEOLOGISTS (AAPG) DOES NOT ENDORSE OR RECOMMEND ANY PRODUCT OR SERVICES THAT MAY BE CITED, USED OR DISCUSSED IN AAPG PUBLICATIONS OR IN PRESENTATIONS AT EVENTS ASSOCIATED WITH THE AAPG. This books and other AAPG publications are available from: The AAPG Bookstore P.O. Box 979 Tulsa, OK Telephone: (918) ; or (800) 364-AAPG (USA-book orders only) Fax: (918) or (800) (USA-book orders only) Australian Mineral Foundation AMF Bookshop 63 Conyngham Street Glenside, South Australia 5065 Australia Tel (08) Fax (08) Geological Society Publishing House Unit 7, Brassmill Enterprise Centre Brassmill Lane Bath BA1 3JN United Kingdom Tel Fax Canadian Society of Petroleum Geologists #505, 206 7th Avenue S.W. Calgary, Alberta T2P OW7 Canada Tel (403) ii

4 About the Editor Ronald C. Surdam serves as director of the Institute for Energy Research (IER), a multidisciplinary research organization founded in November 1993 at the University of Wyoming to address problems relating to the exploitation of natural gas resources, clastic diagenesis, thermal modeling, source rock maturation, petrophysics, and pressure compartmentalization. He received an A.B. in geology in 1961 and a Ph.D. in geology in 1967 from the University of California at Los Angeles. Dr. Surdam joined the geology faculty at the University of Wyoming in 1966, and has served as professor of geology since He was selected as an AAPG Distinguished Lecturer ( ), the Don R. and Patricia Boyd Distinguished Lecturer in Petroleum Exploration (1990), and the AAPG Roy M. Huffington Distinguished Lecturer ( ). Dr. Surdam has served on the National Science Foundation Geology /Geochemistry Advisory Panel ( ), the U.S. Continental Scientific Drilling and Review Group (1990), the American Chemical Society Advisory Panel ( ), and was elected Fellow in the Geological Society of America (1989). He has presented 171 invited lectures, taught numerous short courses and seminars for a variety of corporations and scientific societies, and is the author or coauthor of 170 publications. Dr. Surdam previously served as Associate Editor of the Bulletin of the Geological Society of America (1989), and edited AAPG Memoir 37. Dr. Surdam's current and recent research interests include the San Joaquin and Coastal basins of California, the Gulf Coast, the Western Canada Basin, the Rocky Mountain Laramide basins, the Potiguar and Renconcavo basins of Brazil, the San Jorge Basin of Argentina, the Sinu Basin of Colombia, the Maracaibo Basin of Venezuela, the Mahakam Delta of Indonesia, and the Gippsland Basin of Australia. In all of these areas, he is generally interested in the petroleum system, with special interest in source-reservoir rock relations; fluid-flow characteristics, including sealing mechanisms; clastic diagenesis; and determination of the spatial attributes of hydrocarbon accumulations. iii

5 Acknowledgments Many thanks and congratulations to the following authors and technical reviewers who worked diligently to make this volume possible: David M. Allard C.D. Atkinson George W. Bolger Peter J. Boult Terry Engelder A.E. Fallick J. Foden William R. Almon David K. Baskin Mark P. Fischer Willim Higgs Peter Huntoon Henry P. Heasler Susan J. Hippler Huseyin Is Zun Sheng Jiao John G. Kaldi Mark R. Krolow James Krushin William P. Iverson John G. Kaldi Randi S. Martinsen John McKay Norman R. Morrow AUTHORS REVIEWERS John T. Leftwich T. Leslie Leith Debi T. Maucione Randi S. Martinsen John W. Neasham James C. Niemann Ron A. Noble John W. Neasham Peter D ' Onfro Olivier Poix John H. Sales Leta K. Smith Hugh W. Reid John H. Sales John Sneider Robert M. Sneider Ronald C. Surdam Paul N. Theologou Kadir Uygur M. Arif Yiikler Stephen A. Sonnenberg Robert M. Sneider Ronald J. Steele Brian Towler Charles L. Vavra John Warme I would like thank the Gas Research Institute (GRI) of Chicago for generously supporting various research programs at the Institute of Energy Research (IER); it is fair to say that the bulk of the work presented in Section III of the memoir would not have been undertaken without GRI support. In fact, the innovative ideas of Dave Powley (GRI; formerly of Amoco) provided the impetus to study and apprehend concepts relating to pressure seals and compartments; subsequently, GRI has provided many resources and encouragement to accomplish this task. In addition, I would like to acknowledge Alice Rush, David Copeland, and Laura Vass of the IER at the University of Wyoming for their contributions to the volume. Allory Deiss (IER) created and improved graphics for several authors in the memoir, and has been an invaluable part of this effort. I would also like to thank my co-editor Kathy Kirkaldie (IER), who kept the effort progressing by accomplishing large and small tasks with enthusiasm and optimism and always with a great deal of encouragement. iv

6 Foreword P etroleum explorationists, in the ever increasingly difficult search for hydrocarbons, presently place significant emphasis on integrated studies of source, conduit, seal and reservoir lithologies, and traps (Magoon and Dow, 1994, and others in AAPG Memoir 60). R.J. Murris (1984), in the introduction to AAPG Memoir 35, offers a real and graphic display of the importance of such integrated approaches to oil and gas exploration. In his figure 1, based on an actual case of 165 prospects, Murris (1984) nicely illustrates that ranking prospects by trap size alone increases forecasting efficiency of hydrocarbon accumulations by 28% over a random drilling order. For quite some time it has been apparent that the majority of successful wells are sited on structural closures, but it has been equally apparent that the majority of unsuccessful wells also are sited on structural closure. Murris (1984) demonstrates that by including geochemical charge and retention parameters (e.g., source potential, maturation history, and expulsion efficiency), a forecasting efficiency as high as 63% can be obtained. Murris (1984) argues that it is possible-by integrating source rock studies with structural aspects during the evaluation of a prospect-to reduce exploration uncertainty significantly. Magoon and Dow (1994) promoted a holistic approach to the evaluation of a "petroleum system" by formalizing the integration of data on essential elements and processes characterizing a petroleum accumulation. Ultimately, they hoped that this approach would reduce the risk of exploring for hydrocarbon plays and prospects. They considered source rocks, reservoir rocks, seal rocks, and overburden rocks as the essential elements of a petroleum system, and trapped formation and the generation, migration, and accumulation of petroleum, the vital processes affecting it. After much discussion on petroleum systems with many exploration geologists, it has become clear to me that the least understood element in a petroleum system typically is the seal, and the least understood process in a petroleum system is the trapping of hydrocarbons. To be sure, if explorationists are to reach the 68% forecasting efficiency described by Murris (1984), we must substantially improve our understanding of seals and trapping mechanisms. After all, in many places in the world, our knowledge of structural settings and source rock attributes have been enhanced greatly, yet in these areas forecasting efficiencies do not begin to approach 68%. This AAPG memoir is a serious attempt to reduce uncertainty with respect to hydrocarbon traps and seals. Armed with the knowledge available in this volume and the experiences willingly shared by its authors, explorationists will be able to get beyond the essential knowledge threshold and begin to take the steps necessary to acquire a better conceptual understanding of hydrocarbon traps and seals and produce the diagnostic tools we so desperately need to expedite their development. In my opinion, in most frontier prospective areas, 70% forecasting efficiencies will only become a reality when techniques and technologies are developed to detect, delineate, and quantify the capacity of sealing lithologies, and the critical characteristics of trapping mechanisms are documented. This memoir is divided into the following sections: (I) Seal Characteristics: Processes Controlling Sealing Capacity; (II) Traps: Hydrocarbon Seals in a Regional Context; and (III) Pressure Seals and Fluid Compartments. R.M. Sneider, J.S. Sneider, G. Bolger, and J.W. Neasham start Section I with a description of a new technique to measure sealing capacity using cuttings (i.e., hydrocarbon column heights). Prior to this work, analytical techniques were restricted to core samples; because the coring of fine-grained lithologies occurs mainly by accident, quantitative data on seals remained scarce. With the advent of the techniques outlined in this paper, essential seal data should become much more readily available. A paper by R. Noble, J. Kaldi, and C.D. Atkinson discusses the role of hydrocarbons in fine-grained lithologies and relates it to seal performance. J. Krushin's paper examines the use of pore-throat distribution to seal performance. In contrast, J. Niemann and M.R. Krolow discuss a method to determine if faults exhibit sealing or leaking characteristics. Section II of this memoir addresses seals in a regional context; in other words, the trapping of hydrocarbons. J. Sales starts the discussion with a summary of his lifetime effort to understand the relationship between seal strength and trap closure. This paper is followed by J. Kaldi and C.D. Atkinson v

7 vi Surdam with a neat case history that demonstrates the value of evaluating sealing potential. Next the memoir includes papers by S.J. Hippler, and T.L. Leith and A. Fallick that discuss the role of fractures, diagenesis, and organics in seals associated with North Sea oil fields. D. Allard discusses fault seal interpretation techniques that may improve our understanding of basin-specific seal integrity. P. Boult, P. Theologou, and J. Faden continue the discussion of hydrocarbon traps with a chapter on seal leakage and capillary properties in the Eromanga Basin of central Australia. This section of the memoir concludes with a discussion of carbonate hydrocarbon reservoirs and seals in southeast Turkey by K. Uygur, H. Is, and M. Yiikler. Section III of the memoir deals with pressure seals and pressure compartments, or anomalously pressured hydrocarbon accumulations. R.C. Surdam, Z. Jiao, and H. Heasler start the discussion by describing anomalously pressured gas accumulations in Rocky Mountain Laramide basins. They suggest that gas-saturated pressure compartments are a new class of hydrocarbon accumulation. Next, R. Martinsen determines the difference between a stratigraphic trap and a fluid-pressure compartment. Stratigraphic elements and pressure seals are discussed by Z. Jiao and R.C. Surdam, whereas T. Engelder and J. Leftwich present a case history of the role of faults in the establishment of pressure seals and compartments. D. Maucione and R.C. Surdam next discuss the remote detection of regional pressure seals using seismic reflection data. In the last paper in this section, R.C. Surdam introduces a new exploration paradigm used in the search for anomalously pressured gas/ condensate accumulations, or so-called "pressure compartments." The memoir concludes with an appendix by H. Reid, in which analyses of drillstem test data are used to more accurately assess the leakage potential and reservoir quality of tight formations, even potential seals. In summary, I believe that every explorationist can learn something from the articles contained in this volume. I hope all who read it will more fully appreciate the role of seals and traps in determining the spatial distribution of hydrocarbon accumulations. This AAPG memoir is the outgrowth of a very timely Hedberg Conference sponsored by the AAPG-a conference that clearly demonstrated communication is the key to integrated scientific endeavors. Good luck and success in your search for the everelusive hydrocarbon. Ronald C. Surdam REFERENCES Magoon, L.B., and W.G. Dow, 1994, The petroleum system, in L.B. Magoon and W.G. Dow, eds., The petroleum system from source to trap: AAPG Memoir 60, p Murris, R.J., 1984, Introduction, in G. Demaison and R.J. Murris, eds., Petroleum geochemistry and basin evolution: AAPG Memoir 35, p. x-xii. vi

8 Table of Contents Foreword Section I R.C. Surdam Seal Characteristics: Processes Controlling Sealing Capacity 1 Comparison of Seal Capacity Determinations: Core vs. Cuttings R.M. Sneider, J.S. Sneider, G. W. Bolger, and J. W. Neasham 2 Oil Saturation in Shales: Applications in Seal Evaluation R.A. Noble, J.G. Kaldi, and C.D. Atkinson 3 Seal Capacity of Nonsmectite Shale J. T. Krushin 4 Delineation of a Pressure Fault Seal from Shale Resistivities J.C. Niemann and M.R. Krolow Section II Traps: Hydrocarbon Seals in a Regional Context 5 Seal Strength vs. Trap Closure-A Fundamental Control on the Distribution of Oil and Gas J.K. Sales 6 Evaluating Seal Potential: Example from the Talang Akar Formation, Offshore Northwest Java, Indonesia f.g. Kaldi and C.D.Atkinson 7 Microstructures and Diagenesis in North Sea Fault Zones: Implications for Fault-Seal Potential and Fault Migration rates S.J. Hippler 8 Organic Geochemistry of Cap-Rock Hydrocarbons, Snorre Field, Norwegian North Sea T.L. Leith and A.E. Fallick 9 Fault Leak Controlled Trap Fill: Rift Basin Examples D.M. Allard 10 Capillary Seals Within the Eromanga Basin, Australia: Implications for Exploration and Production P.J. Boult, P.N. Theologou, and J. Faden 11 Reservoir Characterization of Cretaceous Mardin Group Carbonates in Bohikya-Cukurtas and Karakus Oil Fields, SE Turkey: A Petrographic and Petrophysical Comparison of Overthrust and Foreland Zones K. Uygur, H. Is, and M.A. Yiikler vii

9 viii Table of Contents Section III Pressure Seals and Fluid Compartments Appendix Index Anomalously Pressured Gas Compartments in Cretaceous Rocks of the Laramide Basins of Wyoming: A New Class of Hydrocarbon Accumulation R.C. Surdam, Z.S. Jiao, and H.P. Heasler Stratigraphic Controls on the Development and Distribution of Fluid-Pressure Compartments R.S. Martinsen Characteristics of Anomalously Pressured Cretaceous Shales in the Laramide Basins of Wyoming Z.S. Jiao and R.C. Surdam A Pore-Pressure Limit in Overpressured South Texas Oil and Gas Fields T. Engelder and J. T. Leftwich Seismic Response Characteristics of a Regional-Scale Pressure Compartment Boundary, Alberta Basin, Canada D.T. Maucione and R.C. Surdam A New Paradigm for Gas Exploration in Anomalously Pressured "Tight Gas Sands" in Rocky Mountain Laramide Basins R.C. Surdam Evaluating Seal Facies Permeability and Fluid Content from Drill-Stem Test Data H. W. Reid

10 AAPG Wishes to thank the following for their generous contributions to Seals, Traps, and the Petroleum System Amoco Production Company Mobil Exploration and Producing Technical Center Petro Tech Associates John K. Sales Contributions are applied against the production costs of publication, thus directly reducing the book's purchase price and making the volume available to a greater audience. ix

11