Geochemistry in Petroleum Exploration Geochemistry in Petroleum Exploration Douglas w. Waples BROWN AND RUTH LABORATORIES, INC. DENVER, COLORADO ... ~ D. REIDEL PUBLISHING COMPANY " A Member of the Kluwer Academic Publishers Group DordrechtIBostonILancaster INTERNATIONAL HUMAN RESOURCES DEVELOPMENT CORPORATION Boston For Bob Witters and all other excellent teachers Cover illustration: Core 13 from Hole 550 of Leg 80 of the Deep Sea Drilling Project, Goban Spur, North Atlantic. Black, bioturbated clay stones of probable Turonian to Coniacian age grade upward into green and finally red claystones, reflecting the gradual increase in bottom water oxygen content in the Late Cretaceous. The sequence is capped by a white chalk turbidite. See also figure 2.13. Cover and interior design by Outside Designs. © 1985 by International Human Resources Development Corporation. Softcover reprint of the hardcover 1st edition 1985 All rights reserved. No part of this book may be used or reproduced in any manner whatsoever without written permission of the publisher except in the case of brief quotations embodied in critical articles and reviews. For information address: lHRDC, Publishers, 137 Newbury Street, Boston, MA 02116. Library of Congress Cataloging in Publication Data Waples, Douglas, 1945- Geochemistry in petroleum exploration. Bibliography: p. 217. Includes index. 1. Organic geochemistry. 2. Geochemical prospecting. 3. Petro leum-Geology. 4. Gas, Natural-Geology. 1. Title. TN871.W28 1985 622'.13 85-105 ISBN-l3: 978-94-010-8900-5 e-ISBN-l3: 978-94-009-5436-6 DOl: 10.1007/978-94-009-5436-6 Published by D. Reidel Publishing Company P.O. Box 17, 3300 AA Dordrecht, Holland in co-publication with lHRDC Sold and distributed in North America by IHRDC In all other countries, sold and distributed by Kluwer Academic Pub lishers Group, P.O. Box 322, 3300 AH Dordrecht, Holland Geological Sciences Series Series Editor George deVries Klein Department of Geology University of Illinois at Urbana-Champaign Consulting Editors Michael A. Arthur Graduate School of Oceanography University of Rhode Island Thomas W. C. Hilde Department of Geophysics Texas A(]i'M University W. Stuart McKerrow Department of Geology and Mineralogy University of Oxford J. Casey Moore Earth Sciences University of California-Santa Cruz, Contents Dedication iv Preface ix 1. Introduction 1 Philosophy of Hydrocarbon Exploration Formation of Oil and Gas Applications to Hydrocarbon Exploration Suggested Readings 2. Organic Facies 5 The Carbon Cycle Factors Influencing Organic Richness Examples of Rich and Lean Sediments General Models for Source-Rock Development Summary Suggested Readings 3. Organic Chemistry and Isotopes 19 Introduction Names and Structures Stereochemistry and Isomers Reactions Isotopes 4. Kerogen 31 Introduction Kerogen Formation Kerogen Composition Kerogen Maturation Summary Suggested Readings 5. Bitumen, Petroleum, and Natural Gas 43 Introduction Compounds Present in Bitumen and Petroleum vii viii Factors Affecting Composition ofBitu1nen and Petroleum Factors Affecting Thermal Maturity Comparison of Bitumen and Petroleum Interpretation of TTl Values Natural Gas Applications to Hydrocarbon Preservation Summary Applications to Exploration Suggested Readings Comparison of Several Maturity Models Potential Problems with Maturity Calculations 6. Migration 63 Conclusions Definitions Suggested Readings Primary Migration Practice problems Secondary Migration Solutions to Practice Problems Accumulation 10. Correlations 155 Effects on Oil and Gas Composition Significance for Exploration Introduction Suggested Readings Correlation Parameters Correlation Parameters for Gases 7. Analytical Techniques 73 Case Studies Introduction Conclusions Chemical Characterization for Correlations Sugsested Readings Source-Rock Evaluation Practice Problems Contamination and Weathering Solutions to Practice Problems Analytical Costs 11. Surface Prospecting 181 Summary Suggested Readings Philosophy of surface Prospecting Surface-Prospecting Techniques 8. Source-Rock Evaluation 93 Summary Definition of Source Rock Suggested Readings Principles of Source-Rock Evaluation Interpretation of Source-Rock Data 12. Integrated Applications to Exploration 189 Examples of Source-Rock Evaluation Philosophy of the Model-Based Approach Summary Qualitative Models of Hydrocarbon Systems Suggested Readings Quantitative (Volumetric) Models Practice Problems Summary Solutions to Practice Problems Suggested Readings 9. Predicting Thermal Maturity 121 Glossary 205 Introduction References 217 Construction of the Geological Model Special Considerations About Burial-History Curves Index 225 Calculation of Maturity Preface This book is intended primarily as a textbook for geolo gists engaged in petroleum exploration. Its purpose is to introduce the reader to organic geochemistry and to show how to apply geochemistry advantageously in an explora tion program. I have made the explicit assumption that most readers will have a sound background in geology but far less knowledge of, or interest in, chemistry. Be cause there is no need for an exploration geologist to be an expert in organic chemistry, the amount of chemistry used in the book is rather modest. It is, however, often important for a geologist to understand some basic vocab ulary. The emphasis in this book is on applications of geo _chemistry to hydrocarbon exploration. Most of the analyt ical techniques are discussed only briefly, because although a geologist should know what a gas chro matograph is, he or she is unlikely to be asked to repair one. If more detailed knowledge does prove necessary, a laboratory is the proper place to learn. The strengths and weaknesses of the various analytical techniques are discussed so that a geologist will be able to anticipate pitfalls, cull bad data, and choose an appropri ate analytical program. On-the-job experience will prove invaluable in converting the basic information from this text into a practical working knowledge. The heart of the book, I hope, will be the examples showing the application of geochemistry to common ex ploration problems. Practice problems (with answers) are included at the end of several chapters so that the reader can test his or her understanding of basic princi- ix x pIes of geochemical interpretation. My interpretations are there is a short list of recent articles that will be of general not guaranteed to be the very best possible; they could interest to a nonspecialist. At the end of the book is a serve as focal points for classroom discussions. longer list of references cited in the text or figure legends. Because of its design as a textbook for independent Many chemical and geochemical terms are italicized study, graduate courses, or short courses, this book is not where they are first introduced. These and many other intended as a reference volume or encyclopedia. Readers terms are defined more formally in the Glossary. who want to delve more deeply into various aspects of Developing the ability to apply organic geochemistry petroleum geochemistry should consult the primary liter intelligently and effectively in exploration is not difficult, ature that I have cited, or the reference volumes Petro even if one does not have a strong chemistry background. leum Formation and Occurrence by Tissot and Welte This text is designed to foster the development of those (1978) and Petroleum Geochemistry and Geology by Hunt skills. If after reading the book you can find ways to make (1979). geochemistry work for you, then you and I will have The literature cited in this book represents only a tiny succeeded. fraction of that available. At the end of most chapters Chapter 1 Introduction PHILOSOPHY OF HYDROCARBON EXPLORATION There is no one magical technique that removes all risk in hydrocarbon exploration, although we would all wel come such an advance. The most we can ask of the vari ous exploration technologies is that they lower our risk. Given the poor success rates for new-field wildcats, this goal is certainly reasonable and feasible. As we improve our ability to apply science in an exploration context, the savings in both money and time not wasted on dry holes could be phenomenal. Explorationists now have at their disposal a large arse nal of weapons to use against the elusive hydrocarbon. Among these are the various traditional branches of geol ogy, global tectonics, seismic technology, remote tech niques (including satellite and airborne methods and surface- prospecting), organic geochemistry, and inte grated basin analysis. In order to make its exploration program as effective and competitive as possible, a mod ern oil company should utilize all of these technologies in appropriate ways. Applying available scientific data and methods in a cost-effective manner always presents a challenge. Ide ally, the initial reconnaissance phases in a new area should lead to inexpensive high-grading, because much of the original area will subsequently be rejected. More expensive techniques can be used later in the areas of greatest interest. We must also decide how the various exploration tech nologies can best be integrated to create an exploration program that provides, at minimum cost, information of 1