AVO Technology and its application in oildetection.docx

AVO Technology and its application in oildetection.docx

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AVOTechnologyanditsapplicationinoildetection

题目:

AVOTechnology

指导老师:

邹慧芳

学生姓名：

张鹏

所属院系：

地球科学学院

专业：

矿物学、岩石学、矿床学

班级：

矿物S131

完成日期：

2013年11月11日

AVOTechnology

ZhangPeng

Abstract

Withthedevelopmentofoilandgasexplorationandthedeepeningofthedegreeofseismicexploration,conventionalmethodscannotdetectformation（lithology）oilandgasreservoir,thenweusetheAVOtechniquetodetectoilandgas.AVOtechnologywasusedtoidentifythe"brightspots"amplitudeanomaly,aslongasthedevelopmentandapplicationofcomputertechnologyinrecentyears,theAVOtechnologyinthefieldofoilandgasexplorationhasmoreandmoreextensiveapplication.Thispaperbeginsbysearchinglargequantityofliteratures,dataandrelatedbooksfromAVOtechnologydevelopment,AVOprinciple,technicalideas,examples,advantagesanddisadvantagesatthesametimecombinedwiththeoilfieldproductionexampleanalysistheprobabilityofuseAVOtechnologytoimprovetheproductionofoilandgas;LastcometoaconclusionthatinsomeareaswhenuseconventionalseismictechniquescannotdetectoileffectivelythencanuseAVOtechnologytodetectoilandgasinordertoincreaseoilandgasproduction.

keywords:

AVO；AVOTechnology；Poisson'sratio；Forward；inversion；

Oilandgasdetection；

Contents

1AVOTechnology-3-

2PrinciplesofAVOTechnology-3-

2.1ThephysicalbasisofAVOTechnology-3-

2.1.1waveequation-3-

2.1.2Zoeppritzequations-4-

2.2ThegeologicalbasisofAVOTechnology-6-

3ApplicationofAVOTechnology-8-

3.1Thetrueandfalserecognitionhighlights-8-

3.2Detectionofoilgaswaterboundary-9-

3.3Lithologicinterpretation-9-

4Theexampleanalysis-10-

Case1:

-10-

Case2:

-12-

Case3:

-13-

5AdvantagesandlimitationsofAVOTechnology-14-

5.1Advantages:

-15-

5.2Limitations:

-15-

6InfluencefactorsanalysisofAVO-16-

7conclusion-16-

References-16-

1AVOTechnology

AVOisintendedtoamplitudevariationwithoffsetasshowninfigure1.Oramplitudeversusoffset.AVOtechnologyistheuseofCDP（commondepthpoint）gathersdata,analysisofreflectionwaveamplitudeversusoffset（orincidentangle）changerule,estimatePoissonratiooftheinterface,furtherinferredlithologyandhydrocarbon’scondition.

Figure1relationshipbetweenamplitudeandoffset

2PrinciplesofAVOTechnology

TheprincipleofAVOtechnologycontainstwoparts:

thephysicalandgeologicalfoundation.

2.1ThephysicalbasisofAVOTechnology

ThecoretheoryofAVOtechnologyisthewaveequationanditssolution—Zoeppritzequations.ThephysicalbasisofAVOtechnologyisdiscussedthesolutionofwaveequation（Zoeppritzequations）,thespecificapplicationandtheresultingconclusionsinseismicexploration.

2.1.1waveequation

Thewaveequationisdescribedasapartialdifferentialequationwhichvolumeelementoftheelasticmediummovefromtheequilibriumposition.

Intheaboveformula

isLaplaceoperator,Itisexpressedas:

U,V,W,asamediumdisplacementintheX,Y,Zthreedirectionofthecomponent;

asthephysicaldensity（describethedistributionofsource）component,

asmediumdensity.

and

asthemediumofLamecoefficient;

asthevolumestrains.

Zoeppritzequationsisasolutionofthewaveequation.

2.1.2Zoeppritzequations

Assumethattheboundaryconditionsforthewaveequation:

onthesurfaceof1.5infiniteelasticmedium（suchassurface）,aharmonicwavetotheinterfaceofmediumgeneratesfourwaves,whichreflectedP-wave,S-wavereflectionofPSV,P,SVtransmissionwavetransmittedp-wave.

figure2Thereflectionandtransmissionwave

Accordingtotheboundaryconditionsandthesolutionofthewaveequation,bringtheflectioncoefficient,thetransmissioncoefficientandthencangettheZoeppritzequations.

Which

representsthePwavereflectioncoefficient,reflectioncoefficientofSVwave,PwaveandSVwavetransmissioncoefficientandthetransmissioncoefficient.

representsinterfaceonthedensityandvelocity.

astheincidentangle,

astheangleofreflection,

and

asthetransmissionangle.

BringthelaboratorydataintotheZoeppritzequations,Thengettherelationshipbetweentheincidenceangle（oroffset）andreflectioncoefficient（amplitudeofseismicwave）.

figure3Relationshipcurvesofreflectioncoefficientandangleofincidence

Figure3indicatesthattherelationshipbetweentheangleofincidenceandthereflectioncoefficient:

withtheincidentangle（oroffset）change,reflectioncoefficient（amplitude）.

2.2ThegeologicalbasisofAVOTechnology

AftersolvingthewaveequationcanobtaintherelationshipbetweenseismicP-wavevelocityandS-wave:

Intheformula,

and

asLamecoefficient;

asmediumdensity;Eastheyoung'smodulus;

asPoissonratio.

FromtherelationofPandSwavecanleading-outthecomparisonexpressionofP-wavevelocityandS-wavevelocityratio.

TheformulashowthattheratioofPandShearwavevelocityiscloselyrelatedtothePoisson'sratio.VariationofPoisson'sratiodependsonthelongitudinalwavevelocity,themagnitudeofthechangedependsonthespeedofthebasevalueandspeedvariationamplitude.

LaboratoryaccordingtotheshearwavevelocityratioandPoisson'sratioofdifferentdeterminationofthecorrespondingrelationsandtheirchangeswiththerockcharacteristics,testresultsareshowninFigure4.

Figure4differentlithologicrock’srelationsofPoissonratioandaspectBobbi

AscanbeseenfromFigure4,gasbearingsandstonehastheminimumPoisson'sratio（0≤

≤0.16）;and

Increaseswiththeincreaseofporosity,andtheweatheringcrusthasthelargestPoisson'sratio.

Inaddition,DominicalsogivesaPoissongas,oil,watersandratiocurvewiththeburialdepth（Fig.5）

Figure5differentsandstonePoisson'sratiocurvewiththechangeofdepth

Figure5showsthatgasbearingsandstonehastheminimumPoisson'sratio,Itchangesbetween0.02~0.18,oil-bearingsandstone’sratioofPoissonisinbetween（0.24~0.4）,andwatersandhasthemaximumPoisson'sratiorangingfrom0.35to0.5.

ThefollowingexamplesshowthattherelationshipbetweenthePoisson'sratioanddifferentrockproperties,asshowninFigure6:

Fig.6RelationshipbetweenPoisson'sratioandPwaveinteractiondiagram

Poisson’sratioinFigure6clearlyseparatedfromthesandstoneandshaleandlimestone;besides,thePoisson'sratiooflimestoneandshaleishigherthanthatofsandstone.

Tomakealongstoryshort,thePoisson'sratiocandistinguishlithology.Poisson'sratiocanpredictthecharacteristiclayeranditsoilandgasreservoirbyusingseismicdata.

3ApplicationofAVOTechnology

AVOtechnologyhasbeenappliedtovariousareaswithcomplexgeologicalconditions,andhaveachievedgoodresults,herearesomeexamplestoillustratetheapplicationofAVOtechnologyinhydrocarbondetection.

ApplicationofAVOtechnologyinhydrocarbondetectionmainlyconcentratedin:

trueandfalserecognition,severalhighlightsdetectionofoilandgaswaterboundary,lithologicinterpretationandsoon.

3.1Thetrueandfalserecognitionhighlights

"Brightspot"maybeasignofoilandgas,butsomeofthehighlightsarenotcausedbytheoilandgasaccumulation;somenongascontaininghighorlowvelocitylayer（suchaslimestone,igneousrockorcoal）canalsocausestrongamplitudeanomalyamplitude,butnotwithoffsetincreases,soyoucantodistinguishthetruefromthefalsebrightspotsbyAVO,asshowninfigure7.

Fig.7highlightsoftrueandfalseidentification

InFigure7,anincreaseintheamplitudeofCDPgathertwo"brightspot"astheoffsetchanges,buttheincreasingamplitudeabovethe"brightspot"withoffsetandsmaller,falsebrightspots;brightamplitudeversusoffsetbelowincreases,isreallybrightspot.

3.2Detectionofoilgaswaterboundary

Distributionofregionalcomprehensivestudyalllogging,drillingdataandoilgaswaterrangestatistics,Poisson'sratio,reflectioncoefficientbymeansofdifferentlithologyandfluidbearingthesamelithologyimpedanceboundaryconditionwiththechangeofincidentangledifferenttojudgetheoilgaswaterboundary.

Figure8shows,gasinthePoisson'sratiooftheloweramplitude,oil-bearingsandstone,sandstoneandwaterbearingsandstonetopinterfacewithoffset（angleofincidence）changesarenotthesame;gasbearingsandstonetopinterfaceofamplitudevariationwithoffsetmaximum,theamplitudeofoil-bearingsandstone,sandstoneroofwaterinterfacechangeswithoffsetisminimal,soitcanbeusedtojudgetheoilgaswaterboundary.

Fig.8relationshipbetweensandstone

reservoirtopinterfaceamplitudeandoffset

3.3Lithologicinterpretation

TakeadvantageofTheamplitudeandangleofincidencecurveofdifferentlithologybetweenimpedanceinterface,wecaninferenceandinterpretationthelithologywhichthecurverepresented.

（a）（b）

Fig.9usetheamplitudetointerpretlithologic

Figure9（a）diagramisagraphseismicamplitudeandoffset,theamplitudeofdifferentoffsetcorrespondingtodifferentvalues,usingappropriateoffsetvaluecurve,too（b）diagram.ThedifferentoffsetvalueintotheZoeppritzequationscorrespondingtothespeedvalue.AccordingtothereflectionlayerS-waveandP-wavevelocitycanbecalculatedbyusingthePoisson'sratio,Poisson'sratiooftheregionalstratigraphiclithologyexplained.

4Theexampleanalysis

Case1:

ThesouthofAlberta’sCretaceoussandstoneColonyisagoodreservoir,seismicdataalsoshowedthetypicalbrightspotanomaly,FIG