The pressure difference between the pressure exerted by fracturing fluid and the pressure of reservoir matrix at the ends of the fractures can have an important influence on oil-water imbibition and displacement.In this study,using cores col-lected from Chang 7 shale formation,simulation experiments of imbibition and displacement under different fracture end pres-sure difference were carried out under conditions of supplement formation energy with high pressure injection of fracturing flu-id and well shut-in with constant pressure.In the experiments,a dynamic nuclear magnetic resonance(NMR)technique,real-time pressure detection,and visual image analysis were applied to analyze and interpret the influence mechanisms of the fracture end pressure difference.The results show that reverse differential pressure with reverse imbibition can be obviously observed,especially in the process of supplement formation energy by the fracturing fluid,in which,with the increase of the fracture end pressure difference,the efficiency of imbibition and displacement gradually increases.The efficiency of imbibi-tion and displacement is dominated in the micro pores(at 0-6 MPa,the imbibition and displacement efficiency are 33.31%,29.51%,35.65%and 64.89%respectively).In the process of well shut-in with a constant pressure,the reverse differential pressure imbibition is reduced due to the weakening of the differential pressure in micro pores,and the imbibition and displacement process are still dominated by reverse imbibition with capillary force,while oil in large pores can imbibe in-to micro pores.
关键词
缝端压差/页岩油储层/动态渗吸/核磁共振
Key words
fracture end pressure difference/shale oil reservoir/dynamic imbibition/nuclear magnetic resonance
维普
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