Comparative Analysis on Plugging Performance of Multi-size Plugging Microspheres under Pressure Penetration Test
Shale oil and gas resources in China show great potential and micro-fractures are abundant in hard and brittle shale.In the process of drilling and production,fractures expand without effective plugging and the fluid extends fractures into the deep shale,leading to wellbore instability and deep stress changes.Conventional polymer plugging materials are unable to cope with the multi-scale changes of shale fractures,resulting in low plugging efficiency.Moreover,under the action of various rock stress,polymer chain segments may be broken,so that the material ability may become poor,which affects its sealing ability of deep shale fractures.According to the multi-scale characteristics of shale fractures,the relationship between different microsphere systems and plugging performance was studied in this paper.Through the comparison and analysis of the PPT plugging rate between(AM/AA/AMPS)/I-MMT and(AM/AA/ACMO)/GMASG microsphere system,it can be seen that(AM/AA/AMPS)terpolymer microsphere system has better adaptability to shale formations with multi-scale fractures.Through the comparison and analysis of the increasing plugging rate,it can be found that the increasing value of(AM/AA/ACMO)/GMASG system is 13.84%which is 7.88%higher than that of(AM/AA/AMPS)/I-MMT system,which means nanocomposite microspheres can resist rock stress and form a relatively stable plugging layer.Moreover,graphene has a significant effect on protecting and enhancing polymer microspheres.
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