3-D Seismic Interpretation

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3-DSeismic Interpretation

3-D seismicdatahavebecomethe key tool usedin the oil andgasindustryto understandthe subsurface. In addition to providing excellent structual images,the densesampling of a 3-D survey can sometimes makeit possibleto mapresewoirqualityandthe distributionofoil andgas.The aim of this book is to help geophysicists andgeologistsnew to the techniqueto interpret3-D datawhile avoidingcommonpitfalls. Topicscoveredinclude basicstructuralinterpretationand map-making;the useof 3-D visualisation methods;interpretation of seismicamplitudes,includingtheirrelationto rock andfluid propertiesiandthe generationanduseof AVo andacousticimpedancedatasets. Also includedis the increasinglyimportant neld of timelapse seismic mapping, which allows the interpreter to ftace the movement of fluids within the reservoirduringproduction.The discussionof the acquisitionandprocessingof 3-D seismicdatais rntendedto promote an understandingof important data quality issues.Extensive mathematicshas been avoided,but enoughdetailis includedon the effectsofchangingrock andfluid propertiesto allow readers to maketheir own calculations. The authorsofJ-D SeismicInterpretationareprofessionalgeophysicists with manyyears,experience in the oil industry. They are still actively inter?rcting 3-D seismicdataand arc thercfore able to summarise the currentbest practice.The book will be indispensable for geoscientists leamingto use 3-D seismic data, particularly $aduate studentsof geophysicsand petroleum geology, and new enftants into the oil andgasindusty. Mike Bacon was awarded a Ph.D. in geophysicsfrom the University of Cambridge before becoming a Principal Scientific Offrcer at the Institute of Geological Sciencesin Edinburgh (now the British Geological Suwey). After working as a lecturer in the Geology Depanment of the University of Accra, Ghana, he took a position with shell uK where he worked for 19 years asa seismicinterpreter ard asteam leaderin seismic special studies. Dr Bacon is a co-authorof Introduction to seismic Interpretation by Mce'llrin et al. (1979).'d is a memberof the editorialboardof the petroleumindusty magazine FirstBreak.He is a Fellow of the GeologicalSocietyand a memberof the EAGE (EurcpeanAssociationof Geoscientists andEngineers). Robsimm is a geophysicistwith 16 years' experiencein the oil and gasindustryand a specialistin the rock physicsinterpretationof seismicdatain both explorationand production.After gainingan M.sc. and Ph.D. in marinegeologyat UniversityCollegeLondon,the early part of his careerwas spentwith Bdtoil plc and rricentrol plc as a seismicinter?rcter.He subsequently took a positiqnat Enteryriseoil and progressedfrom North Seaexplomtionto productionand equity determination,prior to becoming a'' rntemalconsultantto assetteamsand management. since 1999Dr Simm hasprcvidedindependent consultancyand taining servicesto numerousindependentand multi-national oil companiesthroush his companyRock PhysicsAssociatesLtd. TerryRedshawgaineda Ph.D. in numericalanalysisfrom the unive$ity of wales beforebecominga GeophysicalResearcher with WestemGeophysical.Since1985he hasbeenemployedby Bp in a variety of roles.Thesehaveincludedresearchinto imagingand inve$ion algorithms,as well as leadinga team supplyingBP's worldwide assetswith supportin the areasof seismicmodelling,rock properties,AVO and seismicinversion.Dr Redshawworks.atpresentin Bp,s ExplorationExcellenceteam,which helps operatingunits to carry out the tecbnical wo* neededto evaluateoil prospectsand decidewhether to drill them or not.

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3-DSeismic Interpretation M.Bacon R,Simm T,Redshaw

CAMBRIDGE

UNTVERSITY PRESS

PUBLISTTED BY TIIE PRESSSYNDICATE OF TIIE UNIVERSITY OF CAMBRIDCE

The Pitt Building, TrumpingtonStreet,Canbridge,Unitei Kingdom The EdinburghBuilditrg, Canbridge CB2 2RU, uK 40 west 20rhSreeL New York, l.[Y 1001l-4211,USA 477 WilliamstownRoad,Port Melboume,VIC 3207,Ausfialia Ruiz de A1arc6n13,28014Madrid, Spain Dock House,The Waterftont,CapeTown 8001,SouthAfrica http://ww\t cambridge.org @M. Bacon,R. Simm andT. Redshaw2003 This book is i$ cop].right.Subjectto statutoryexception and to the provisionsof rclevantcollectlvelicensingagreements, no reproductionof any part may takeplacewithout the written perrussionof CarnbridgeUnivenity hess. First published2003 Pdntedin drc Unit€d Kitrgdomat the Unilersity hess, Cambddge Typefaces'fimesl0,5ll4 pt. ard HelveticaNeue

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A cataloguerecordfor this book is awilable Irom theBritish Library Library of CongressCataloguingin Publicationdata Bacon,M. (Michael), 194G 3-D seismicinterpretation/ by M. Bacon,R. Simm, T. Redshaw. p. cm. Includesbibliographicalreferclces andindex. ISBN 0 521 79203? (hadback) 1. Seismicreflectronmethod, 2. Seismicprospecting. 3. Petroleum- Geology. 4. Natual gas Geology. I. Titlei Three-Dseismicinterpretation. II. Sirffn, R. (Robert),1959T. (Terence), 1957 IV Tide. m. Redshaw, QE539.824 2003 62/.1 592-4c21 20O3Mr2Or ISBN 0 521 792037 hardback

Gontents

Preface

page rx

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1

Introduction

1.1

Seismicdata Migration of seismic data Data density Usesof seismicdata Roadmap Conventions:seismicdisplay.units Unit conversions References

2 3 7 9 13 14 15 16

2

3-Dseismic dataacquisition andprocessing

17

2.1 2.2 2.3 2.4 2.5 2.5.1 2.5.2 2.5.3 2.5.4 2.5.5 2.5.6

Marine 3-D dataacquisition Marine shearwave acquisition 3-D land acquisition Other types of seismic survey 3-D dataprocessing Reformat,designature, resamplingandgain adjustment Deconvolution Removingmultiples Binning Stacking and migration Post-migrationprocessing References

1.2 1.3 r.4 1.5 1.6 1.7

I

18 26 30 34 35 35 39 39 43 46 53 .)l

vi -

Contents

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3

interpretation Structural

Well ties 3.1 3.1.1 The syntheticseismogram 3.1.2 TheVSP Workstationinterpretation 3.2 3.2.1 Displaycapabilities 3.2.2 Manualhorizonpicking 3.2.3 Autotrackers 3.2.4 A ributes 3.2.5 Viewingdatain 3-D Depthconversion 3.3 methods 3.3.1 Principlesof vertical-sfretch 3-3.2 Use of well velocityinformation 3.3.3 Use of seismicvelocities 3.3.4 I-ateralshifts References

57 57 58 66 71 72 77 8l 84 88 89 89 94 96 98 100

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4

interpretation Geological

102

4.1 4.2 4.3

Seismicresolution Seismicsffatigraphy Interpretation tools Someexamples Faults References

ro2

5

seismic amplitudes Interpreting

120

5.1 5.2 5.3 5.4 5.5 5.5.1

Basicrock properties Offsetreflectivity Interpretingamplitudes AVO analysis Rock physicsfor seismicmodelling Fluid effects

120 171 tz5 130 139 140

4.4 4.5

106 109 113 117 118

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Contents

5.5.1.1 Calculatingfluid parameters 5.5.1.2 Calculatingmdtrix parameters 5.5.1.3 Invasioneffects 5.5.2 P-wavevelocityandporosity 5.5.3 P-wavevelocityandclay content 5.5.4 P-wavevelocity anddensity 5.5.5 Shearvelocity 5.5.6 Dry rock moduli 5.6 Assessingsignificance References

143 144 1/t