致密油藏水力压裂后水锁形成及演化规律

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中图分类号：TE348 文献标志码：A

Abstract：Inordertoinvestigatestheoccurrenceandevolutionofwaterblockageintightoilreservoirsfolowinghydraulic fracturing，integratedcoreexperimentswerecariedoutinthisstudy，whichcansimulatetheentirelifecycleofpost-fracturing process，including soaking，flowback，and production.A nuclear magnetic resonance（NMR）technique was employed to visualizethe migrationoffracturingfluidwithinthefracture-matrix system.Theexperimentalresultsshow thatfracturing fluidpredominantlyinvades themediumandlarge poresof thereservoir matrix，creatingareas withhigh-watersaturation near thefracture surfaces.The primary mechanism behind water blockage occurrence isidentified as thecapillaryend effect， whichresultsfromcapilarydiscontinuitybetweenthematrixandthefractures.Duringtheflowbackstageoffracturingfluid， water blockagecanbe partiallyallviated，occurring inthree phases：arapidunlocking period，aslowunlocking period，and astable locking period.Therapidunlocking period isdriven bypressurediferentials，allwing partialrestorationofoilproductionasthefracturing fluiddrains fromlarge pores.During the slowunlocking period，capilaryforces predominate，movingthefluid fromlargertosmaller poresand deeper intothe matrix torelease theblockage.Implementing longersoaking period can hinder the spontaneous releaseof waterblockageduring theflowback stage and exacerbate its damaging efects.Conversely，increasing the pressre differentialcan enhancethe spontaneous releaseofwater blockage，weaken thecapilaryend effect，expand the oil phase's stable seepage channels，and ultimately improve the oil production rate.

KeyWords： tight oil reservoirs； hydraulic fracturing；water blockage；NMR；capillary end effect

致密油作为重要的非常规资源，是接替常规油气能源、保障中国能源安全的重要力量[1-3]。（剩余14343字）