Computed Tomography for Rock-Property Determination and Fluid-Flow Visualization

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1、ComputedTomographyforRock-PropertyDeterminationandFluid-FlowVisualizationE.M.WlthJack,SPE,AreoOil&GasCo.Summary.ThispaperdiscussesthedevelopmentandapplicationofX-raycomputedtomography(CT)forthedeterminationofrockpropertiesandthestudyofmiscibledisplacementsinlaboratorycores.Saturation(relativeperm

2、eability)andporositymeasurementsbyCTscanningaredescribed,andtheresultsarecomparedtothoseofconventionalmethods.Resultsofcorefloodswithmisciblefluidsshowtheinfluenceofrockheterogeneities(beddingplanes)andmobilityratioonvolumetricsweepout.Thecorefloodsalsoillustrateanewdisplaytechniquethatcombinesas

3、eriesoftwo-dimensional(2D)CTslicesintothree-dimensional(3D)perspectiveviews.IntroductionTheuseofCTforobservingfluidflowinrockandnondestruc•asprojectiondata.Rotationofthesourceanddetectorsduringscan•tivelyviewingitsinteriorpromisesnewknowledgeinpetroleumningallowsforacquisitionofprojectiondataalon

4、gmanylinesfromengineeringandtheassociatedgeologicalsciences.Unlikeconven•differentdirections.tionalX-raymethods,CTusesacomputertoreconstructa2Dim•3.ImageReconstruction.Thisstepinvolvesfindingthelinearage,orslice,intheplaneofanX-raybeamdirectedthroughanattenuationcoefficientsforallthevolumeelement

5、salongthelinesobjectfrommanydifferentdirections.Conventionalmethodsformbetweenthesourceandthedetector.Radon9establishedthemath•animagebyprojectingcompositeX-rayattenuationpatternsematicalfoundationsforimagereconstructionfromprojectiondata.(shadows)ofanobject'sinternalfeaturesontoasingleplane.AMod

6、ernmethodsarebasedontransformalgorithms.lO,llseriesofCTslicestakenashortdistanceapartcanshow3Dfea•4.ImageDisplay.TheelementsofaCT-displayscreen[cathodetureswithinanobject.raytube(CRT)]representthelinearattenuationcoefficientsofcor•TheuseofX-raystostudyoilrecoveryinthelaboratorywasrespondingvolume

7、elementsinascannedobject.TheCTcomputerpioneeredoverthreedecadesago.1,2TheearlyworkofSlobodandconvertsattenuationcoefficientsintocorrespondingnumericalCaudlelintroducedtheX-rayshadowgraphtechnique,aconven•values,orCTnum