粘弹性流体平行于界面的力可以提高驱油效率

水驱后残余油的微观形态可划分为油滴状、油膜状和簇状残余油3种类型.前人研究工作表明,若要用牛顿流体驱动水驱后的残余油,其驱动力必须要再增加1000～10000倍才能克服束缚残余油的毛管力,而实际油藏中的粘滞力不可能增加如此之大.虽然聚丙烯酰胺水溶液对油水界面张力影响不大,但实验室内和矿场试验数据表明,用聚合物水溶液驱替后,孔隙介质中所有类型的残余油均减少,减少的量取决于驱替液的弹性.实验条件相似的流体,其弹性越大,驱替后残余油饱和度越低.微观可视岩心模型实验研究结果证实,粘弹性驱替液可降低不同润湿性岩心的残余油饱和度.粘弹性驱替液驱替残余油的力与牛顿流体的力不尽相同,它不仅有垂直于油水界面克服束缚残余油的毛管力,而且还有较强的平行于油水界面驱动残余油的拖动力.

IMPROVEMENT OF DISPLACEMENT EFFICIENCY OF CORES BY DRIVING FORCES PARALLEL TO THE OIL-WATER INTERFACE OF VISCOUS-ELASTIC FLUIDS

Microscopic residual oil in reservoir after water flooding can be classified into three types:oil droplets,oil films and oil clusters.Former research work shows that in order to overcome the capillary forces trapping the residual oil after water flooding,the driving viscous forces must increase by one thousand to ten thousands times than before.In fact,the viscous forces in the reservoir can not increase to such a magnitude.Though polyacrylamide(PAM)solution has little effect on the tension of oil_water interface,the lab test and field data show that all types of residual oils in pores are reduced after PAM flooding.The magnitude of reduction is related to the elasticity of the solution.The higher the elasticity is,the lower the saturation of residual oil will be.Research results of flooding visualization cores show that viscous_elastic fluid flooding can decrease the residual oil saturation of cores with all types of wettabilities.The driving force of viscous_elastic fluid is different from that of Newtonian fluid.The viscous_elastic fluid not only has a viscous driving force perpendicular to the oil_water interface for overcoming the capillary trapping force,but also has a strong viscous dragging force parallel to the oil_water interface for pulling all types of residual oils after water flooding.