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APPLIEDTECHNIQUESTOINTEGRATEDOIL ANDGASRESERVOIRCHARACTERIZATION
APPLIEDTECHNIQUES TOINTEGRATEDOIL ANDGASRESERVOIR CHARACTERIZATION
AProblem-Solution
Discussionwith GeoscienceExperts
Editedby
EnwenodeOnajite
NigeriaAssociationofPetroleumExplorationists(NAPE),Lagos,Nigeria SocietyofExplorationGeophysicists(SEG),Tulsa,Oklahoma,UnitedStates
Elsevier
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Notices
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Practitionersandresearchersmustalwaysrelyontheirownexperienceandknowledgeinevaluatingandusinganyinformation, methods,compounds,orexperimentsdescribedherein.Inusingsuchinformationormethodstheyshouldbemindfuloftheirown safetyandthesafetyofothers,includingpartiesforwhomtheyhaveaprofessionalresponsibility.
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Contents
Listofcontributorsxi
Forewordxiii
Acknowledgmentsxv
I
GEOLOGICALARCHITECTURE OFUNCONVENTIONALAND DEEPWATEROFFSHORE
RESERVOIRS
1. Unconventionalanddeepwaterreservoir architecture
OLEKSANDROKPREKYI,ZAWWINAUNG, ALEXEYSOKOLOV,RAJESHWARANDANDAPANI, ROBERTAVAKIAN,NEILW.CRAIGIE,SUSANNASHAND THARWATHASSANE
Basinanalysis:overviewanduses4
Usesofbasinanalysis4
Basinanalysisworkflow:fromlarge-scaletominiscale7
Geologicalarchitectureofunconventionalreservoirs12
Deepwaterreservoir33
References36
Furtherreading36
II
STRUCTURALAND STRATIGRAPHY INTERPRETATION
2. Qualitativeseismicinterpretation
FREDW.SCHROEDER,GERARDOCLEMENTEMARTINEZ, HESHAMSHALABY,JAAPVANDERTOORN, JOSEADAUTODESOUZA,MATTHIJSVANDERMOLEN, MOHAMEDOAUBEL,RAMYRAGAB,ROBERTAVAKIANAND ZAWWINAUNG
Understandyourseismicdata40
Advantagesofseismicdata41
Disadvantagesofseismicdata41
Two-dimensionalseismicdata42
Three-dimensionalseismicdata42
Seismicdatainterpretationandanalysis44
Datasetneededforseismicinterpretation44
Seismicinterpretationstep-by-stepmethods45
Structuralanalysis48
Structuraltrap52
Faultinterpretation54
Gridding56
Tyingloops56
Techniqueusedtoenhancefaultinthree-dimensional seismicdata57
Faultpicking58
Seismichorizonmapping63
Sequencestratigraphyinterpretation64
Reduceuncertaintiesinreservoirpredictionsusing sequencestratigraphyandseismic inversion67
Unconformities68
References70 Furtherreading71
3. Chemostratigraphyanditsapplicationin integratedreservoircorrelation
NEILW.CRAIGIE
Introduction73
Analyticalmethodology75
Assessmentofdataquality80
Geochemistryandmineralogy81
ConstructionofAchemostratigraphicscheme94
CasestudyonthechemostratigraphyofDevonian, Carboniferous,andPermiansediments, EasternSaudiArabia104
Concludingremarks110
References112
III
SEISMICATTRIBUTESAND THINRESERVOIRBED ANALYSIS
4. Amplitudeandattributeanalysisfor reservoircharacterization
ALFREDOSA ´ NCHEZGONZA ´ LEZ, MATTHIJSVANDERMOLEN,MOHAMEDOAUBEL ANDRAJESHWARANDANDAPANI
Seismicamplitudeanalysis120
Seismicattributesanalysis122
Applicationofseismicattributes125
Analysisofdifferentseismicattributes127
Theuseofintervalattributesonaninterfaceproperty129
Seismicattributeasdirecthydrocarbonindicator130
Directhydrocarbonindicator130
Directhydrocarbonindicatorfluidcharacteristics130
Poststackattributes138
Prestackattributes140
Spectraldecomposition140
Techniquesusedforspectraldecomposition142
Applicationofspectraldecompositionforreservoir characterization142
Thinreservoirbedcharacterizationusingawedge model145
Howtodetectfaultsinthinbedusingseismic attributes146
Attributeanalysisincarbonatereservoir149
Seismicattributeforunconventionalreservoirs150
References151
Furtherreading152
IV
PETROPHYSICALANALYSIS FORRESERVOIR CHARACTERIZATION
5. Nuclearmagneticresonanceandits applicationsforreservoircharacterization
Introduction156 Historicaldevelopment157
Purposeofnuclearmagneticresonance logging157
Applicationofnuclearmagneticresonance data158
Combinablemagneticresonancetool(Schlumberger Brand)158
Combinablemagneticresonancesonde159
Combinablemagneticresonancecartridge159
Howdoesnuclearmagneticresonancework?160
Alignment160
Tipping160
Precessionanddephasing162
Refocusing163
Irreversibledephasing:transverserelaxation time(T2)164
Realignment164
Nuclearmagneticresonancerelaxation mechanisms166
Nuclearmagneticresonanceapplicationsforreservoir characterization167
Lithology-independentporosity167
Shaledelineationinradioactivesandsand carbonate167
Multidimensionalnuclearmagneticresonancefluid characterization167
Casestudyfromrealdatafrommiddleeastcarbonate reservoirusingnuclearmagneticresonance168
Magneticresonancefluidmethod171
Methodanddataprocessing173
Fluididentificationandsaturation173
Viscositycomputation174
Resultsandconclusions176
Loggingconditionsanddataquality176
T2 domainprocessingindicatingthereservoir quality178
Saturationandviscosityanalysis178
Estimatingnuclearmagneticresonance-derived permeabilityinsandstones178
Linkingnuclearmagneticresonanceto permeability179
Lowresistivitypay182
Howthenuclearmagneticresonanceisaffectedbyoil viscositiesandTAR186
Newapproachforsolvingheavyoileffectonnuclear magneticresonancepermeability187
IntegrationofMDTandcombinablemagneticresonance permeability189
Gasdetectionfromnuclearmagneticresonanceand DPHI(densityporosity)189
THARWATHASSANE
Nuclearmagneticresonancesupportin geosteering191
In-flowcontroldevicedesignandnuclearmagnetic resonance192
Furtherreading192
V
SUBSURFACEVELOCITY ANDTIME DEPTH CONVERSION
6. Subsurfacevelocitymeasurement
ADELLHAKIM,JAAPVANDERTOORN,HAMMADHASSAN TARIQANDZAHEERALISHAH
Understandingvelocitydata195
Check-shotdata196
Application197
Verticalseismicprofilefieldoperation198
Check-shotandverticalseismicprofilefieldoperation: practicalapplication202
Differencebetweencheck-shotandverticalseismic profiledata203
Howtoconvertverticalseismicprofileintoawelllog curve204
HowtoQCverticalseismicprofiledata206 Planning206 Execution206 Processing207
Howtodeterminethestaticcorrectionforvertical seismicprofiledata209
Verticalseismicprofilesreplacementvelocity211
Walk-awayverticalseismicprofilefieldoperation211
7. Time-to-depthconversion
JAAPVANDERTOORN,GERARDOCLEMENTEMARTI ´ NEZ, GRANTHANSON,HAMMADHASSANTARIQ, HESHAMSHALABY,MATTHIJSVANDERMOLEN ANDZAHEERALISHAH
Importanceoftime depthconversion215
Velocitydatausedfordepthconversion216
Theaccurateseismicvelocityfordepthconversion217
Depthcalibrationtechnique221
Velocitymodelingfordepthconversion222
Inputdatasetsusedforvelocitymodeling222
HowtoQCvelocitymodelfordepthconversion223
References229
Furtherreading230
8. Seismicpetrophysicsandpetrophysicalwell curvesanalysisforquantitativeseismic interpretation
ENWENODEONAJITE
SeismicPetrophysics:Introduction233
Whatisquantitativeseismicinterpretation?235
Densitylog238
Soniclog240
References248
Furtherreading248
9. Well-to-seismictie
GERARDOCLEMENTEMARTI ´ NEZ,GRANTHANSON, HAMMADHASSANTARIQ,JAAPVANDERTOORN, JOSEADAUTODESOUZA,MATTHIJSVANDERMOLEN, OLEKSANDROKPREKYI,RAJESHWARANDANDAPANI ANDZAHEERALISHAH
Objectiveofwell-to-seismictie251
Inputdataforwell-seismictie252
Uncertaintiesinwell-to-seismictie253
Time depthrelationshipforwell-tie253
Bulkshiftandstretchissueswhendoingwell-to-seismic tie258
Stretch/squeezetoimprovewellsyntheticstoseismic match260
Kneepickinginsoniccalibration263
Differencebetweentimeandphaseshiftinwell ties263
Howtodeterminethewaveletusedforsynthetic trace264
Syntheticseismogram265
Reasonswhywedosyntheticseismograms265
Depth depthcurvesyntheticseismogram269
Seismicattributesfromsyntheticseismic data269
References271
10. Gassmann’sfluidsubstitution
MICHELKRIEF
Fluidsubstitution273
Forwardstratigraphymodeling279
Porosityconceptsinfluidsubstitution281
References282
Furtherreading283
11. Waveletextraction/derivation
BRIANSCHULTE,GERARDOCLEMENTEMARTI ´ NEZ, HAMMADHASSANTARIQ,JAAPVANDERTOORN, JOSEADAUTODESOUZAANDRAJESHWARANDANDAPANI
Waveletextraction285
Waveletextractionmethods286
Seismicphaseanalysis291
Seismicpolarity292
Howtopredictthephaseofawaveletinthinreservoir bed298
Reference300
12. Amplitude-variation-with-offsetanalysis andinterpretation
ALFREDOSANCHEZGONZALEZ,BRIANSCHULTE, MATTHIJSVANDERMOLEN,MOHAMEDOAUBEL, RAJESHWARANDANDAPANIANDROCKYDETOMO
Understandingamplitude-variation-with-offset analysis302
Datacalibrationsforamplitude-variation-with-offset analysisandreservoircharacterization303
Amplitude-variation-with-offsetattributes306
Factorsthataffectamplitude-variation-with-offset analysis311
Reflectioncharacteristicsofsandandshale313
Amplitude-variation-with-offsetclassification313
Class2Pamplitude-variation-with-offsetresponse317
Effectofmultipleinamplitude-variation-with-offset modeling319
Amplitude-variation-with-offsetanalysisincarbonate reservoir326
References327
Furtherreading328
13. Seismicinversionforreservoir characterization
ALEXEYSOKOLOV,BRIANSCHULTE,HESHAMSHALABY ANDMATTHIJSVANDERMOLEN
Factorsthatcontributetogoodinversion331
Benefitsofseismicinversion332
Datasetsneededforseismicinversion332
Seismicinversiontechniques333
Benefitsofdeterministicinversion336
Areaswheredeterministicinversionwillwork better336
Low-frequencymodeluseforseismicinversion343
Howtodeterminethelow-frequencymodel343
Simultaneouselasticinversion346
Performingseismicinversiononhigh-resolution2D seismicdata349
DifferencebetweenAVOanalysisandseismic inversion350
Advantagesofcoloredinversionovertraceintegration method350
References351
Furtherreading351
POREPRESSUREAND WELLBOREINSTABILITY
14. Porepressureandwellboreinstability
JOSEADAUTODESOUZA,GERARDOCLEMENTE MARTINEZ,MARCELF.CASTROPONCEDELEON,MORTEZA AZADPOURANDVAHIDATASHBARI
Porepressureprediction356
Howtoestimateporepressurepriortodrilling356
Relationshipbetweenshaleanisotropyandpore pressure363
Porepressurepredictionusingseismicdataandwell data363
Pressuregradientandfracturegradient367
Methodsofporepressureprediction373
Impedance-basedporepressureprediction374
PorepressurepredictionusingEaton’smethod375
PorepressurepredictionusingBowers’method378
Porepressurepredictionincarbonatereservoir382
Porepressurepredictioninanunconventional reservoir383
Postdrillporepressureprediction386
Howtovalidateyourporepressureresult388
Wellboreinstability390
RTporepressureanalysis393
References393
Furtherreading394
4DSEISMICFORRESERVOIR CHARACTERIZATION
15. 4D(3Dtimelapse)forreservoir characterization
ENWENODEONAJITE
Whatdoesa4Dachieveinreservoircharacterization?399
Useof4Dreservoirmonitoring399
Understanding4Dseismicresponseand interpretation399
Typesof4Dchangestoareservoir401 Kindsoftime-lapsereservoirmeasurements402
Areaswhere4Dseismicmonitoringisapplicable404
Reference405
Furtherreading405
Advicefromtheindustry:careerguideto geosciencesstudentsandhowtoprepare forinterview407
Index413
Listofcontributors
VahidAtashbari UniversityofAlaskaFairbanks, SouthChandalarDrive,Fairbanks,AK,United States
ZawWinAung ExplorationGeologistatMPRL E&P,Myanmar
RobertAvakian OklahomaStateUniversity, InstituteofTechnology,Okmulgee,OK,United States
MortezaAzadpour NationalIranianOilCompany, Tehran,Iran
MarcelF.CastroPoncedeLeon Senior GeomechanicsEngineer,EseasaOffshore, Tampico,Tamaulipas,Mexico
NeilW.Craigie GeologicalConsultantatSaudi Aramco,Dhahran,SaudiArabia
RajeshwaranDandapani TelestoEnergy,Chennai, India
JoseAdautodeSouza ExploratoryVision,Macae ´ , Brazill
RockyDetomo GeophysicalConsultingatOmoted E&PConsulting,NewOrleans,Houston& Florida,UnitedStates
AlfredoSa ´ nchezGonza ´ lez IngenieroGeo ´ logo Especialista&Consulting,Me ´ xico,Mexico
AdellHakim GeophysicalConsultantat MAGNUMEGYPTforConsultancy,Training andDevelopment,Egypt
GrantHanson Consultant-SeismicData Processing,Houston,TX,UnitedStates
TharwatHassane PetrophysicalTechnicalLead, Beicip-FranlabAsia,KualaLumpur,Malaysia
MichelKrief ConsultantPetrophysicist,Krief Models,GreaterParisMetropolitanRegion, France
GerardoClementeMartı ´ nez PEMEX, Villahermosa,Tabasco,Mexico;PEMEX Exploracio ´ nyProduccio ´ nS.A.deC.V., Villahermosa,Mexico
MatthijsvanderMolen ShellInternationalE&P, TheHague,Netherlands
SusanNash InnovationandEmergingScienceand Technology,UniversityofOklahoma,Tulsa MetropolitanArea,UnitedStates
MohamedOaubel PETRONAS,Montreal,Quebec, Canada
OleksandrOkprekyi Sr.GeologistatBurisma, Kyiv,Ukraine
EnwenodeOnajite NigeriaAssociationof PetroleumExplorationists(NAPE),Lagos, Nigeria;SocietyofExplorationGeophysicists (SEG),Tulsa,Oklahoma,UnitedStates
RamyRagab Sr.ExplorationGeophysicistat EdisonS.P.A.,Cairo,Egypt
FredW.Schroeder ExxonMobil(retired),Houston, TX,UnitedStates
BrianSchulte CSEGRecorder,GreaterCalgary MetropolitanArea,Canada
ZaheerAliShah SeniorManagerExplorationand BoreholeSeismicSpecialist,PETRONAS,Kuala Lumpur,Malaysia
HeshamShalaby DragonOil,Cairo,Egypt
AlexeySokolov ReservoirEngineering,CGGVostok,Moscow,RussianFederation
HammadHassanTariq ExperienceLead(Sr.) BoreholeGeophysicist,Weatherford International,Houston,UnitedStates
JaapVanderToorn ShellInternationalE&P (retired),TheHague,Netherlands
Foreword
Inhisnewbook,Onajitecontinuesthework begunin SeismicDataAnalysisTechniquesin HydrocarbonExploration (ISBN:978-0124200234) inbringingup-to-dateinformationandtechniquestogeophysicistsandgeologistsworking attheforefrontofexplorationanddevelopment.Thisnewofferingfocusesprimarilyon thegrowingintegrationofgeophysical,geological,reservoirengineering,production,and petrophysicaldatainpredictinganddeterminingreservoirproperties.Asbefore,discussions ofthevarioustopicsarefollowedbyrealworldproblemsgarneredfromworkingprofessionals.Answersarenotonlycontributedto byotherinterpreters,buttheworkisalsoreinforcedbyagroupofdedicatedprofessionals, manywithimpressiveresumes,whoaddextra dimensiontotheproblemsandanswers.
Readingthebookinsequence,whichis recommended,startsyouatthebeginningof theexploitationeffort,withbasinevaluation. Youthenmovethroughunconventionalreservoirs,structuralandstratigraphictrapinterpretation,time-to-depthconversionandits manynuances,andseismicpetrophysics/reservoirgeophysicsandapproachthebook’send withporepressurepredictionand4Dseismic reservoirmonitoring.Indoingsoyouexperience,inalogicalandsupportedorder,thecuttingedgeofreservoirpropertydetermination
throughtheuseofintegratedgeophysical/geological/engineeringteams.Ofcourse,youmay diveintothebookatanyplaceyouchoose,but youwillnothavethebenefitofthepriormaterialstoaidinyourunderstanding.
Thelastchapterisoneyouwillrarelyseein print:“AdvicefromtheIndustry:CareerGuide toGeosciencesStudents,”whichissubtitled, “UnderstandingWhatItIsToWorkInAn IntegratedGeoscienceTeam.”Manyoldhands, havingworkedinteamsmadeupofgeologists, geophysicists,andengineers,maybetempted toskipoverthislastchapter.Butthisisanew kindofteam,andinanycase,allofuscanbenefitfromarefresherincooperationamongprofessionalswithdifferingbackgrounds.This chaptershouldberequiredreadingforallnew hiresseveralweeksbeforetheirfirstdayonthe jobandperiodicallythereafter.
Nosinglebookcantreattheentirerangeof reservoirsandthewaysofdeterminingtheir properties.Yet,athoroughreadingofthisparticularbookwillpreparetheworkingprofessionalfortherigorsofidentifyingand determiningpropertiesofsignificantreservoirs beingexploitedtoday.
RobertAvakian OklahomaStateUniversityInstituteofTechnology, Okmulgee,OK,UnitedStates
Acknowledgments
Iammostgratefultothemanyglobalgeoscientistexpertsandprofessionalswhohave helpedandinspiredmeinthewritingand developmentofthisindustry-orientedpractical book.
SpecialthankstoShellE&PInternational, SaudiAramco,SaudiArabia,TotalE&P, Nigeria,PGSgeophysical,CGGVeritas, PETRONAS,TelestoEnergy,India, ExploratoryVisionandUSEnergyInformation Association(EIA)aswellastoSocietyof ExplorationGeophysicists(SEG),United States,and CanadianSocietyofExploration Geophysicists (CSEG)fortheirimmersecontributionstothisbook.
ThankyoutoSusanNash,PhD,Directorof InnovationandEmergingScienceand Technology,UniversityofOklahoma,United States,ZawWinAung,ExplorationGeologist atMPRLE&P,OleksandrOkprekyi,Sr. GeologistatBurisma,andAlexeySokolov, ReservoirEngineeringTeamLeadatCGGfor theircontributionstothechapteronbasinanalysis,unconventionalreservoirs,anddeepwaterreservoirs.
ThankyoutoMatthijsvanderMolen, GeoSignsSeniorGeophysicistatShell InternationalE&P,andAlfredoSanchez Gonzalez,GeologistatNetBrainsServices, Mexico,fortheirwillingnesstoassistandfor theircontributionstothechapterson3Dseismicinterpretation,seismic-to-welltie,and time-depthconversion.
ThanksalsotoDr.FredW.Schroeder, GeologistatExxonMobil(Retired),forgranting
methepermissiontousehismaterialsforthe chapteronstructuralandstratigraphicseismic interpretation.Andalso,toRamyRagab,Sr. ExplorationGeophysicist,forhiscontributions tothischapter.
ThankyoutoJaapVanderToorn,Learning AdvisorGeophysicistatShell(Retired),and AdellHakim,GeophysicalConsultantand BoreholeSeismicExpert,Egypt,fortheir immersecontributionstothechapterson seismic-well-tieandtime-depthconversion.
ThankyoutoDr.NeilW.Craigie, GeologicalConsultantatSaudiAramco,Marco Vecoli,SaudiAramco,andConradAllen, SaudiAramco,SaudiArabia,fortheircontributionstothechapteronchemostratigraphy anditsapplicationinintegratedreservoir correlation.
ThanksalsotoJoseAdautodeSouza,Senior Geophysicist,SeismicInterpreterat ExploratoryVision,HeshamShalaby,Sr. Geophysicist,DragonOil,Australia,and GerardoClementeMartinez,Sr.SeismicData Processing/ImagingExpert,fortheircontributionstothechaptersontime-depthconversion andwaveletextraction.
ThankyoutoZaheerAliShah,Senior ManagerExplorationandBoreholeSeismic Specialist,Canada,foryourcontributionsto thechaptersonseismic-to-welltieandtimedepthconversion.
ThankstoDr.TharwatHassane,Reservoir Engineer/PetrophysicistatSchlumberger,BP andBakerHughes(retired),forhiscontributionstothechapteronpetrophysicalanalysis
forreservoircharacterizationaswellastothe chapteronunconventionalreservoirs.
ThankyoualsotoRajeshwaranDandapani, DirectorGeophysicsatTelestoEnergy,India, BrianSchulteInternationalMultidisciplinary GeoscientistatSchieferReservoirConsulting, andMohamedOaubel,Sr.Geoscientists, PETRONAS,fortheircontributionstothe chaptersonseismicattributeanalysis,AVO analysis,andseismicinversion.
ThankyoutoProf.JackDvorkin,Rock PhysicsScientist,andMichelKrief,Consultant Petrophysicist AcousticLogsSpecialist,for theircontributionstothechapteronGassmann fluidsubstitution.
ThanksalsotoVahidAtashbari,Pore PressureExpert/AssistantProfessor, UniversityofAlaskaFairbanks,UnitedStates, andMarcelF.Castro,SeniorGeomechanics Engineer,Mexico,fortheircontributionstothe chapteronporepressureprediction.
ThankyoutoRockyDetomo,HeadQI,Shell Nigeria(retired)andGeophysicalConsultant atOmotedE&PConsulting,forhiscontributionstothechaptersonAVOanalysisandseismicmonitoringforreservoircharacterization.
ThankstoErickAlvarez,ColinMacBeth, andJonathanBrainfortheirworkon4Dseismicforreservoirmonitoring.Theircontributionshelpedmedevelopthechapteron4D seismicforreservoirmonitoring.
ThankyoutoRobertAvakian,Instructor, OklahomaStateUniversityInstituteof Technology,UnitedStates(retired),forediting themanuscriptandcontributingtothegeneral structureofthebook.Youbroughtexcellence tothisbook.
ThanksalsotoBayoOjulari,MDShell NigeriaExplorationandProductionCompany andNedoOsayande,formerGMCorporate SocialResponsibility,ShellNigeria(retired), forgrantingmeaccesstotheoilandgas industry.
Withaheartfullofappreciation,Isaythank youtoPastorChrisOyakhilome,PhDfor buildingastrongGodlycoreinmeandfor instillinginmetherightmindsettosucceedin anyendeavorinlife.
Finally,Iamgratefultothegiveroflife,the creatoroftheuniverse Godalmightyandthe sweetHolySpirit fromwhomtheinspiration andtheabilitytocreatethisbookcomesfrom.
SECTIONI
GeologicalArchitectureof UnconventionalandDeepWater OffshoreReservoirs
Thispageintentionallyleftblank
Unconventionalanddeepwaterreservoir architecture
OleksandrOkprekyi1,ZawWinAung2,AlexeySokolov3, RajeshwaranDandapani4,RobertAvakian5,NeilW.Craigie6, SusanNash7 andTharwatHassane8
1Sr.GeologistatBurisma,Kyiv,Ukraine 2ExplorationGeologistatMPRLE&P,Myanmar
3ReservoirEngineering,CGG-Vostok,Moscow,RussianFederation 4TelestoEnergy,Chennai,India 5OklahomaStateUniversity,InstituteofTechnology,Okmulgee,OK,UnitedStates 6Geological ConsultantatSaudiAramco,Dhahran,SaudiArabia 7InnovationandEmergingScienceand Technology,UniversityofOklahoma,TulsaMetropolitanArea,UnitedStates 8PetrophysicalTechnical Lead,Beicip-FranlabAsia,KualaLumpur,Malaysia
OUTLINE
Basinanalysis:overviewanduses4
Usesofbasinanalysis4 Whatisasedimentarybasin?5 Riftbasins5
Basinanalysisworkflow:fromlarge-scaleto mini-scale7
Large-scaleanalysis7
Medium-scaleanalysis8
Small-scaleanalysis9
Geologicalarchitectureofunconventional reservoirs12
Unconventionalandtightgassands:whatwe knownow12
Shaleoilandgas12 Oilshale13 Tarsands16 Tarsandextractionandprocessing16
Coal-bedmethane17
Tightgasreservoirsands18
Earlyshaleplayproductionprojectionsand subsequentadjustments20
UpperSafaformation21
Techniquesforunconventionalreservoir evaluationandcharacterization22
Geochemicalanalysis24
Totalorganiccarbon24
Levelofmaturity25
Basinanalysis:overviewanduses
Basinanalysisisofvitallyimportantinoil andgasexploration.Itincorporatestheprocesses usedtodeterminewherethereisahighlikelihoodofencounteringcommercialquantitiesof recoverablehydrocarbons,andthusisintegralto prospectgeneration(Fig.1.1).Intheoilandgas industry,thepetroleumgeologistdeterminesthe possiblepresenceandextentofhydrocarbons andhydrocarbon-bearingrocksinabasin.Basin analysisisoftenperformedbyusingreflection seismologyanddatafromwelllogging.
Usesofbasinanalysis
Basinanalysisisusedinmorethansimply generatingprospects.Geoscientistshaveexpanded basinanalysisbyincorporatingnewtechnologies andtechniques.Itcannowbeusedfor:
• identifyingsweetspotsthroughprojecting enrichmentalongmigrationpathways;
• determiningthebestfluidstouseindrilling andcompletions;
• developingareservoirmodel,andfor estimatingrecoverablereserves;and
• identifyingandavoidinggeohazards.
FIGURE1.1 Crosssectionofsedimentarybasinwherepetroleumsystemanalysisiscarriedout.FromAAPGslide show.Source:CourtesyExxonMobilandF.Schroeder.
FIGURE1.2 GeologyandhydrocarbonpotentialoftheoffshoreIndusBasin,Pakistan.Source:Carmichael,S.M.,etal., 2009.GeologyandhydrocarbonpotentialoftheoffshoreIndusBasin,Pakistan.Petrol.Geosci.15,107 116. https://doi.org/10.1144/ 1354-079309-826
Whatisasedimentarybasin?
Abasincanbeformbysagrelatedtoafault (Mukherjee,2014).Basinanalysiscoverssedimentarybasins,whichareareasontheEarth’s surfacewheresedimentshavebeendeposited. Generallyspeaking,basinsarequiteextensive andcancovertensofthousandsofsquarekm (Fig.1.2).Sedimentarybasinscanbeverydeep andalsoshallow.Deepbasinsareoften markedbyhighpressuresandtemperaturesat depth.
SedimentarybasinsformbecauseoftectonicactivityintheEarth’scrust.Crustalsubsidenceoccursovertime,whichresultsin punctuatedepisodesofsedimentaccumulation,deformation,andstructuralactivity. Thereareseveralmechanismsthatresult insedimentarybasins,andtheyincludethe following.
FIGURE1.3 Riftbasin.Source:From http://homepage.ufp. pt/biblioteca/RoleOfSaltTectonicsInPetroleumSystemsAngolaGu lfOfMexico/Pages/Page1.htm.
Riftbasins
Thesesedimentarybasinsemergeduetothe actionofsea-floorspreading.Theyarevery
importantforoilandgasexplorationbecause theytendtohaveadequateflow,whichgenerate oilandongoingthermodynamic/thermochemicalprocessesandthisencouragethemovement ofoilalongmigrationpathways(fractures,faults, connectedporespaces,etc.)(Fig.1.3).
Compressional-convergentplatebasins:These occurwherethereisstructuralmovement, whichcreatesnormalfaultswithsignificant throw,andthesubsequentsheddingofsedimentsfromupliftsandtopographichighs (Fig.1.4B).Itisimportanttokeepinmindthat tectonicactivitycanoccurinmanydifferent pulseswithinabasin,andafewpulsesmay notcovertheentireextentofthebasin.
Technicalquestionandpracticalsolutions QUESTION1
Ifallelementsofapetroleumsystemarein place,canoneestimatethepossibilityof“Trap Breaching”afterhydrocarbonsmigrationfrom
FIGURE1.4 Conceptualmodelsfordepocenter migrationandaxialsedimentsupplyinfault-bend basins.(A)Progressiveright-lateralmigrationof pairedbendsonthefootwallgeneratescompressionalupliftandextensionaldepressiononthe hangingwall.Sedimentsarealwayssuppliedfrom thesamedirectionalongthelong-axisofthebasin. (B)Depocenterfixesalongthereleasingbendresult fromtheright-lateralmigrationofsedimentsdepositedonthefootwall.Atranspressionalcomponent wouldberequiredtogeneratethesedimentsource, andene ´ chelonfoldsmayformalongthemaster faults.Bothmodelsgeneratedepositswithaxial sedimentswhosethicknessesaregreaterthanthe burialdepths.Source:Reproducedwithpermission fromAtsushiNoda.
sourcerock,priortodrillinganexploratory well?
TechnicalsolutionprovidedbyOleksandr Okprekyi
Sr.GeologistatBurisma
Definitely.However,itdependsonhowyou willknowthatallelementsofapetroleumsystemareinplace.Isitanareaadjacenttoan existingfieldandthatisourguess?Isitanoffsetarea?Andthisisonlyahypothesisbased ongrossanalogues.Isitanalreadydrilled area?Inanycase,ifalltheelementsarein place,weshouldconsiderwhethertheelementsaremalleableduetotheongoingburial environment,increasingoverburdenpressure, formationpressure,temperature,newtectonic movements,etc.Onecanassessthispossibility basedonthecontextofavailableanalogues, outcrops,andcontemporaryseismicdataand otherthanseismicpredrilldata.
TechnicalsolutionprovidedbyZawWin
Aung
ExplorationGeologistatMPRLE&P, Myanmar
Basedonmyexperiencethroughtheprospect evaluationworkflowvia3Dseismicdata,there arereasonstoleak(breach)thehydrocarbon (HC)fromacandidateprospect.Ourasset blocksarelocatedinacomplexfoldbeltinduced bytranslationalmovementofIndiaalongthe Myanmarplatecomplex.Thereareseveralfolds andfaultswithmultiphasestructuraldeformationthatdominatewithsyntectonicdeposition ofmassflowdepositsandturbiditieschannels depositsthroughoutthearea.
Iwouldfocusonsealcapabilitybeingnoticeableingoodqualityseismicdataintermsoftrap effectiveness.Ihavetwoexamplesforyouasfollows;thesetwoaremorecriticalinourstudy basin(RakhineOffshoreBasin,Myanmar):
1. Subtlefaultsaffectedbytectonism:Eventhough wehaveallelementsinplace,weneedto investigatethepossiblesealfailurerelatedto minorfaultsinstructuralcrest,whichcanbe seenonseismicdatabutnotinterpretable.In thiscase,wehavetocheckotherindications likeleakagepaths(strangeamplitude responsesalongandnexttothefault).
2. Caprocklithology:Someprospectshavea goodsealsupportedbyverytransparent seismiccharacteristics(shale/clays).Some showfairamplitude(likelysiltyclay,which canleakHCfromreservoir)butarenotas brightasyourunderlyingreservoir.Based onthis,youcanevaluatethedegreeofrisk inyourprospect.
TechnicalsolutionprovidedbyAlexey
Sokolov
ReservoirEngineeringTeamLeadatCGG
Theproblemoftrapbreachingcouldbe addressedbydirectassessmentoffactorscausing
breaching.Asbreachingismostlydrivenbyfaulting,itispossibletoderiveappropriatemetricsfor correspondingcommonvolumeelementsbased onfaultscrossingthetrapandtheircharacterin ordertoupdatechanceofsuccess.Leakingpetroleummightbetrappedupsectioninknownand/ orbetterpronouncedreservoirsorappearas hydrateassociationontheseabottom.Dataon petroleumseepsandslicksonthesurfacemight provideadditionalinsightsonthetrapbreaching.
Basinanalysisworkflow:fromlarge-scale tomini-scale
Large-scaleanalysis
Thisisessentiallyreconnaissanceawork, whichcanbedoneonbothfrontierbasinsand thosethathavebeendeveloped.Itisoftena goodideatoreturntoabasinandconducta reevaluationofthebasin,especiallyifnew dataareavailable,andifnewprocessingmethodscanresultinanewwayofviewingexisting seismic,drilling,completion,andproduction information.ThestepsdefineBasinanalysis workflow:fromlarge-scaletomini-scale.
Step1:Definetheextentofthebasin.The basinframeworkcanbedeterminedbythe mostimportantregionalstructuralfeatures. Notethetectonicframeworkaswell,andto locatethebasinwithinplatemovement. Step2:Identifythemainstructuralfeatures andthedepocenters.Dependingontheextent towhichthebasinhasbeendeveloped,itmay bepossibletoincorporatewelldata.Ifnot, initialbasinanalysisgenerallyrequirestheuse ofsatelliteimagery,seismic,gravity,magnetic, andinformationfromoutcrops.Outcrop informationisoftencorrelatedwithseismic data(e.g., Misraetal.,2015; Misraand Mukherjee,2018)inordertocreatea preliminarysubsurfacebasinmodel,which includesmajorstructuralfeaturesaswellasan ideaofsedimentdepths.Thisisagoodstage
tostartstudyingthesedimentsverycloselyin ordertoproposedepositionalenvironments anddepositionalmodels.Byproposing workinghypotheseswithrespecttothe depositionalenvironmentsofeachofthe formationsandbasinthermalhistory,itis possibletostarttodeterminewhichones couldbegoodsourcerocks,orreservoirrocks.
Step3:Incorporatepetroleumsystem information.Itisoftenpossibletoconduct testsoncoresortocalculatetotalorganic content(TOC)usingthePasseymethod. FavorablelevelsofTOCandtypesof kerogencanindicatewherethereisthe possibilityoffindingeconomicallyviable recoverablereservesofhydrocarbons.The nextstepwouldbetocontinuewith geochemicalmethodsanddetermine maturationbyusingvitrinitereflectance (VR)orothertests.Further,obtaining thermalinformationcanprovide informationusefulindecidingwhetherthe thermalhistorywasadequatefor maturationandthegenerationof hydrocarbons.
Step4:Determinethestructural, depositional,andpostdepositionalhistory (e.g., MukherjeeandKumar,2018),atbasin level.Determiningthetimingofmajor structuraleventsisextremelyimportantfor determiningthetimingofhydrocarbon generation,andthen,theexpulsionand migrationthroughfaults,fracturenetworks, andporousconnectedsediments.Itisalsoa goodtimetoidentifypossiblestructural traps,bydefiningreservoirrock,seals,and migrationpathwaysintothepossibletrap.
Oncethelarge-scaleanalysishasbeencompleted,itisveryimportanttostartidentifying subbasins,subbasinleveldepocenters,and localstructuralmovements.Themedium-scale analysisisimportantinnarrowingdownthe scopeandstartingtorankthesedimentsand subbasinsintermsofrelativeprospectivity.
Medium-scaleanalysis
Depositionthatresultsfromcontinuedepisodesoftectonicactivity(mainlysubsidenceor uplift)andthecompartmentalizationofthebasin intosubbasinsandmini-basinsisimportantfor startingtopinpointlikelyareasforoilandgas.
Step1:Identifysubbasinsandmini-basins. Step2:Createcrosssectionsthatreflectthe stratigraphicarchitecture,thatincorporate availableinformationanddata.Use2D,3D, and4Dseismicinordertoidentifyfaults, thicknessesofsediments,andthechanges throughtime.
Step3:Includeanyfieldlocation informationinthestudy.Selectthemost prospectivesubbasinsandstarttomap majordepositionalevents.Anexampleis theCretaceousonlapoftheGulfofMexico (Fig.1.5).Keepinmindthatseparatingout thesand-pronesedimentsystemwillaidin age-specificstudiesthatincorporatethetime sequenceandmovementoverthedeposits. Step4:Begintomaphydrocarbontypes,as wellasreservoirfluids.Thenplacethese withinaframeworkofstructure,sothatitis clearwherethemajorfaultsandstructural featuresexist,aswellasfracturenetworksat aslowasnanoscale.Wherepossiblecombine thisinformationwiththermalflowsinorder togainanideaofmaturation,expulsion, migration,andthenthepossiblediagenesis patternsduetohydrothermalfluids. Diageneticalterationiscriticalbecause alterationcanbothenhanceanddestroy porosity(sparrycalcity).Chertcanclogpore space,butdolomitizationcanresultin enhancedintercrystallineporosity.Possible sealsandtraps(structuralandstratigraphic) canbeidentified,andtherelativelikelihood ofcommercialdepositscanbeassessed.This isthepointintheanalysiswhenitis possibletostartcreatingatime-focused (chronostratigraphic)modelofthe
sediments.Sequenceboundaries (unconformitiesorcorrelativeconformities) correlatetodepositionalsequences.Theycan helponemapwherethetransgression surfaceoccurred,andalsothepointof maximumflooding.Theresulting“genetic” depositionalsequencesareextremelyhelpful inbeingabletomapthelateralextentand thicknessesofdifferentformations.
Small-scaleanalysis
Whilemanygeoscientistshavelookedat thesmall-scaleanalysis(e.g., Kojietal.,1990; Movahedasl,2015)stageastheoneinwhich drillableprospectsareidentified.Yet,with newtechniquesofdatamining,geochemical analysis,geomechanicalmodeling,andmicroseismicanalysis,itispossibleduringthisstage toidentifysweetspotsforacquisitionordrilling,planfluidsfordrillingandcompletion, andtodevelopareservoirmodelappropriate forenhancedoilrecovery.
FIGURE1.5 Regionalseismic linesshowingcharacteristicstyleof salttectonicsin(A)onshoreproximalpartofGulfofMexicoand (B)offshoredistalpartofGulfof Mexico.Source:DatafromFonck,J. M.,Cramez,C.,Jackson,M.P.A., 1997.The5thInternationalConference ofBrazilianGeophysicalSociety.
Structuralmovementandmigrationpathways: Movementalongfaults,theopeningandclosing offracturesandfracturenetworks,alongwith nanoscalestructuralbehaviorduetohydrocarbongeneration(gas)andexpulsioncanbeused forproposingmigrationpathwaysandpinpointingareasofcomparativeenrichment.Beingable tomapfaciespatternscanalsoidentifyrelative permeabilityandporosity,andtheultimatestoragecapacityinthereservoir.Thusinitialand verypreliminaryreservepotentialscanbeestimated.Large-scaleanalysisofsurfacelineaments (DasguptaandMukherjee,2019)ascorrelatedto differentsubsurfacestructuralfeaturescanprovidenewinsights.Usingacombinationofwell loginformation,petrophysics,andmicroseismic datacanalsohelpdevelopmini-basinmodels thatcanpinpointlikelygeohazards.
Hydrothermalfluidmovement:Byunderstandingwhereheatedfluidsspentthemosttimein thereservoir,andunderstandingtheirchemical composition(aswellasthelithologyofthereservoirrock),itispossibletoprojectwherethere maybeporosityenhancementviadissolutionor
