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Geophysical MonoGraph series

Number 16

First steps iN seismic iNterpretatioN

Donald A. Herron

Rebecca B. Latimer, managing editor

tulsa, oklahoma

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ISBN 978-0-931830-56-3 (Series)ISBN 978-1-56080-280-8 (Volume)

Society of Exploration GeophysicistsP.O. Box 702740Tulsa, OK 74170-2740

2011 by Society of Exploration GeophysicistsAll rights reserved. This book or parts hereof may not be reproduced in any form without written permission from the publisher.

Published 2011Printed in the United States of America

Cover background image courtesy of Thomas H. Wilson

Library of Congress Cataloging-in-Publication Data

Herron, Donald A., 1949- First steps in seismic interpretation / Donald A. Herron ; Rebecca B. Latimer, managing editor. p. cm. -- (Geophysical monograph series ; no. 16) Includes bibliographical references and index. ISBN 978-1-56080-280-8 (volume : alk. paper) -- ISBN 978-0-931830-56-3 (series : alk. paper)1. Seismology. 2. Geophysical surveys. I. Latimer, Rebecca B. II. Title. QE534.3.H47 2011 551.22--dc23

2011047720


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iii

contents

about the author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vpreface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiacknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

chapter 1: introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

chapter 2: seismic response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

chapter 3: seismic attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Coherence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Inversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

chapter 4: Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Sonic logs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Well-velocity surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Seismically derived velocities . . . . . . . . . . . . . . . . . . . . . . . . 41Velocity anisotropy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Time-depth conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

chapter 5: migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

chapter 6: resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

chapter 7: correlation concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . 83First look . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83Horizons versus faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84Multiple reflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Manual versus automatic tracking . . . . . . . . . . . . . . . . . . . . 96Artifacts and interpretation pitfalls . . . . . . . . . . . . . . . . . . . . 105


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iv

chapter 8: correlation procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 115Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115Loop tying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120Jump correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133Correlations in depth-migration projects . . . . . . . . . . . . . . . 140Visualization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145Interpretation processes and work flows . . . . . . . . . . . . . . . . 149

chapter 9: Data Quality and management . . . . . . . . . . . . . . . . . . . 153Data quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153Data management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158Nomenclature systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

chapter 10: other considerations . . . . . . . . . . . . . . . . . . . . . . . . . . 163Gridding and contouring . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1634D seismic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165Seismic modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167Interpretive judgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167Curiosity and interpretive thinking . . . . . . . . . . . . . . . . . . . . 170The interpretation paradox . . . . . . . . . . . . . . . . . . . . . . . . . . 174Approximations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174Uncertainty and risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176The workstation environment . . . . . . . . . . . . . . . . . . . . . . . . 178Ergonomics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179Presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180Career development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181Advanced interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184Time spent and value added . . . . . . . . . . . . . . . . . . . . . . . . . 185

references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193


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vabout the author

Don Herron received a bachelor of sci-ence degree (with honors) in geological sci-ences from Brown University in 1971 and a master of science degree in geological sci-ences from the California Institute of Tech-nology in 1973. He enjoyed a career as a seismic interpreter at Texaco (19731977), Gulf (19771984), and most recently Sohio/BP (19842008). Since retirement in 2008, he has worked as an independent geophysi-cal consultant for Petroleum Geo-Services (PGS) as a geosciences advisor, and with several oil companies as a seismic interpre-

tation instructor. At Gulf and Sohio/BP he taught in-house courses in seis-mic interpretation and was co-instructor for the SEG Continuing Education course Seismic Interpretation in the Exploration Domain (19952007). He was a member of the Editorial Board of The Leading Edge (20022007, chairman in 20062007) and is author of the bi-monthly Interpreter Sam column in The Leading Edge. He is an active member of SEG, AAPG, and Sigma Xi.


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vii

preface

This book begins with an introduction that is more philosophical than technical, followed by five chapters on fundamentals of reflection seis-mic (titled Seismic Response, Seismic Attributes, Velocity, Migration, and Resolution). The gist of what I really have to say about the correlation of seismic records is in Chapters 7 (Correlation Concepts) and 8 (Correlation Procedures). Chapter 9 (Data Quality and Management) certainly should not be glossed over, and Chapter 10 (Other Considerations) contains my thoughts on several worthy topics that do not fit neatly into any of the pre-ceding chapters.

In large part, this book is a compilation of notes from seismic inter-pretation courses that Ive had the good fortune to teach over the past three decades. Because Ive assumed that readers are familiar with basic concepts and principles of geology and reflection seismology, the book is best viewed as a synthesis rather than a fundamental treatment of those concepts and principles. When I use the expression geologically reasonable to qualify interpretation results, which I do throughout the book, I mean reasonable in the sense of analogous to known geology or consistent with known geology or sound geologic models or within the context of expectation or realization of some geologic concept or model.

I certainly dont intend this book to be the definitive primer on inter-preting reflection seismic data or a comprehensive treatise on the latest in correlation tools and techniques; rather, Im seeking to give voice to a con-cern about this particular art that Ive had ever since my first foray into interpretation in the early 1970s. My concern is founded on a statement by a man from whom I had the privilege to learn about exploration geophysics in the classroom and in the field. In his own book he wrote that the cor-relation procedure itself is of such a nature that it can hardly be adequately described in a book.

Well, with the utmost respect for that man, here goes.


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ix

acknowledgments

I thank Rebecca Latimer, Bill Barkhouse, Bruce Hart, and John OBrien for their constructive reviews of my manuscript and also BP (Amal Ray and Tim Summers), PGS (Nathan Oliver), TGS (Tom Neugebauer), and West-ernGeco (Lee Hooper) for permission to include data and images from their companies in this book. I thank Mike Schoenberger for sharing his charac-terization of seismic data quality with me; its the most concise and practi-cal description of data quality Ive ever known, so Ive used it to set context throughout the book. I extend my thanks also to members of the SEG publi-cations and graphics groups in Tulsa, in particular Jennifer Cobb and Kathy Gamble, without whose skill and patience this book could not have come into being. Im especially grateful to Kathy Pile and Gary Stewart, whose editing gave my text the clarity and consistency it needed. In creating this book, Im indebted to countless geoscientists, old and young alike, from whom Ive learned so much over the years. Among all those talented men and women, I owe the most to Tim Smith, perhaps the most insightful inter-preter Ive ever known and an excellent teacher as well, with whom Ive had the distinct privilege numerous times to share the front of a classroom.


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Interpretation is telling the geologic story contained in seismic data. It is correlating the features we see in seismic data with elements of geology as we know them. The story is read from a book having many chapters, some of which are either illegible or unintelligible, and others are lost or yet to be written. And although the story doesnt always have a happy ending, only in its telling do we expand our knowledge.

Interpreter Sam


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