Interaction between Hydraulic Fracturing Process and Pre-existing Natural Fractures

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1、InteractionbetweenHydraulicFracturingProcessandPre-existingNaturalFracturesChunfangMENGContents1Introduction11.1General11.2Applicationofhydraulicfracturing11.3Problemstatement11.4Experimentalapproach21.5Modelingapproach21.6Thesisstructure22Acousticimagingoffractureevolution32.1Introd

2、uction32.2Experimentalset-up32.3Acousticdataprocessing5Taperingtransmissionsignalsandvisualizingdiffractionsignals6Calculationofdiffractortrajectories7Acousticimagingperformance102.4Fracturegeometryestimation13Extrapolatedfracturewidth14Relatingwavetransmissionstothefractureopening15

3、MonitoredResultsagainsttests192.5Discussion222.6Conclusion233Mechanicalandhydraulicpropertiesofanaturalrockfractureundercompressionandshear243.1Summary243.2Experimental24Tri-axialsetup24Acousticsystem25Samples26Injectionsystem30Testprocedure30Experimentalresults323.3Fracturemodeling4

4、1Approximateaperturedistribution41Physicsandnumericalscheme41Modelresults423.4Conclusionanddiscussion454Hydraulicfractureinitiationinnaturallyfracturedrock464.1Summary464.2Testprocedure46Fracturefacegeometryestimation484.3Resultsandinterpretation49Testsummary49Loadingcycle50Injection

5、cycle54Fracturepropagationimaging60Injectionefficiency60Postmortemobservation614.1Interactionbetweenthehydraulicfractureandnaturalfractureopening62Eventsequenceidentifiedbyacousticsignals62iGelinjection654.5ConclusionsandRecommendations661Modelinghydraulicfracturinginelasticrockmedia

6、671.1Summary671.2Generalconcept67Tensilefracturingmechanism67Cohesiveboundary68Quasi-staticequilibrium68Propagationcondition69Geometriesandorientations691.3Mathematicalformulation70Linearelasticmediaandcohesiveboundary70Flowfield731.4Numericalmodel74Fluid-solidinteraction74Approximat

7、ecohesivezoneevolution76Timedependentleak-off77Iterationstructureandconvergence78Adaptivemeshing801.5Modelresults811.6Discussionandconclusion886Modelinghydraulicfracturepropagationinteractingwithnaturalfractures896.1Summary896.2Physicalmechanismofthefracturecrossingdiscontinuities89M

8、odeldomainge