微胶囊聚合物在多孔介质中的渗流与驱油特征

Seepage and oil displacement characteristics of microencapsulated polymer in porous media

关键词:  微胶囊聚合物  抗剪切  缓释增黏  渗流规律  驱油特征

Key words:  microencapsulated polymer  shear resistant  slow release and thickening  seepage law  oil displacement characteristics

摘要:

目的 针对常规驱油用聚合物在注入过程中不抗剪切、黏度损失大、影响驱油效果的问题，采用乳液聚合+界面聚合方式，在聚丙烯酰胺外部引入壳层，合成一种聚氨酯包裹聚丙烯酰胺的微胶囊聚合物。方法 研究了胶囊聚合物破壳前后微观形貌及粒径、缓释增黏性、抗剪切性、注入性、剖面调整能力和驱油效果。结果 结果表明，破壳前微胶囊尺寸为170~800 nm，破壳释放聚合物后，分子尺寸为50~350 nm；65 ℃下加热2 h后开始破壳释放，20 h后黏度释放率在80%以上；吴茵搅拌器强力剪切3 min再破壳，黏度保留率仍在92%以上；破壳前聚合物在50×10^-3~500×10^-3 μm²的岩心中均能有效注入，但剖面调整能力较弱，破壳后聚合物在渗透率大于100×10^-3 μm²的岩心中可增加注入压力，且具有良好的剖面调整能力；水驱后注入微胶囊聚合物可提高采收率15.5个百分点；矿场注入微胶囊聚合物后，井口压力增加明显。结论 微胶囊聚合物在地层中具有破壳增黏能力，是一种有良好应用前景的新型驱油聚合物。

Abstract:

Objective In view of the problems that in the injection process conventional polymers for oil displacement are not shear resistant, and the viscosity loss is large, which affect the oil displacement effect, the method of emulsion polymerization and interfacial polymerization is adopted to introduce a shell outside the polyacrylamide to synthesize a polyurethane encapsulated polyacrylamide microencapsulated polymer. Method This paper studied the microstructure and particle size before and after shell breaking, as well as the slow release and viscosity increasing performance, shear resistance, injection ability, profile adjustment ability, and oil displacement effect.Result The result showed that the size of microcapsule before shell breaking was between 170―800 nm, and after releasing the polymer, the molecular size was between 50―350 nm; after heating at 65 ℃ for 2 h, the shell began to break and release, after 20 h, the viscosity release rate was above 80%; the Wuyin mixer vigorously sheared for 3 min before shell breaking, the viscosity retention rate was still above 92%; the polymer could be effectively injected into rock cores with a permeability of 50×10^-3―500×10^-3 μm² before shell rupture, but its ability to adjust profiles was weak. After shell breaking, the polymer could increase injection pressure in rock cores with a permeability greater than 100×10^-3 μm² and had good profile adjustment ability; injecting microencapsulated polymer after water flooding could enhance oil recovery by 15.5 percentage points. After injecting microencapsulated polymer into the mine, the wellhead pressure increased significantly. Conclusion It proves that microencapsulated polymers can break the shell and increase viscosity in the formation, and it is a new type of oil displacement polymer with good application prospects.