Microdisplacement Mechanism of Polymer Flooding and Distributional Characteristics of Remaining Oil in Heavy-Oil Reservoirs

Most of the heavy-oil reservoirs in China belong to little fault blocks. These reservoirs are characterized by high heavy-oil viscosity, severe reservoir heterogeneity, and poor water-flooding development effect, resulting in low oil recovery and exploitation difficulties. Methods to enhance oil recovery are widely investigated both in China and abroad. They also provide an important approach to guarantee the energy supply in China. Modern physical experiments and simulation methods, such as laser confocal experiments and micro-displacement analysis, are used to study the micro-displacement mechanism of polymer flooding and the distributional characteristics of the remaining oil in heavy-oil reservoirs. The results show that polymer flooding can synergistically affect the reservoir and form a plug with the high viscosity heavy oil. High viscosity heavy oil has a better profile control effect and an expanding swept volume effect of displacement than that of thin oil. In the process of heavy oil polymer flooding, most of the remaining oil occurs in a surface-bound state in the pores of the formation, forming a laminar film type on the surface. In-depth research on improving the physical properties of heavy oil and core wettability after the polymer flooding operations is important for further enhancing the recovery in the heavy-oil reservoirs.