Study On Displacement Mechanism Of Cluster Remaining Oil After Polymer Flooding By Heterogeneous Composite System

Due to the increasing consumption of oil and the difficulty of exploitation,it has become a hot issue to further improve oil recovery while oil reserves remain unchanged.Our oil exploitation mainly relies on chemical flooding technology,and polymer flooding technology takes a leading position in chemical flooding technology because of its simple operation,low cost and easy access to raw materials.However,after polymer flooding,the distribution of microscopic remaining oil in the reservoir is more dispersed,and a variety of different types of remaining oil are formed,among which the remaining cluster oil content is the largest,and the distribution range is wider and more dispersed.In this paper,aiming at cluster remaining oil after polymer flooding,the heterogeneous composite system is used to drive oil by using gel particles blocking large pores in heterogeneous composite system,and the displacement mechanism of heterogeneous composite system on cluster remaining oil after polymer flooding is studied.The results provide research direction and theoretical support for guiding the exploration of residual oil after polymer flooding.In this paper,the effects of polymer solution on oil displacement were studied by the combination of microscopic visualization oil displacement experiment and numerical simulation calculation with COMSOL Multiphysics software,and the occurrence state and formation mechanism of microscopic remaining oil after polymer flooding were analyzed.Aiming at the cluster remaining oil after polymer flooding,the cluster remaining oil model after polymer flooding was constructed by COMSOL simulation software.The effect of gel particle PPG in heterogeneous composite system on the blocking of large pores in porous media and the flow direction of liquid was used to simulate the flooding effect of heterogeneous composite system by changing related parameters affecting the capillary number.The simulation calculation of different displacement phase viscosity,interfacial tension,wettability and displacement velocity was carried out.The displacement effect of heterogeneous composite system solution on cluster remaining oil after polymer flooding was analyzed under different displacement conditions.The changes of remaining oil saturation,pressure in porous media after heterogeneous composite system flooding and enhanced oil recovery after polymer flooding were studied.The results show that,for polymer solution flooding,the oil recovery under the condition of high concentration polymer flooding is about 20% higher than that under the condition of common polymer flooding,and it is more beneficial to improve the oil displacement efficiency when the wettability is water.As for the cluster remaining oil after polymer flooding by heterogeneous composite system,since gel particle PPG in heterogeneous composite system has the effect of blocking large pore channels and causing the flow direction of subsequent displacement phase liquid,the enhanced recovery value of heterogeneous composite system flooding after polymer flooding is different under different conditions.When the viscosity ratio of heterogeneous composite system to oil phase is 1,3and 10,the improved recovery value is 9.88%,12.73% and 19.87%,respectively.When the interfacial tension is 3m N/m,0.3m N/m and 0.03 m N/m,the improved recovery value is12.73%,32.78% and 38.42%,respectively.When the wettability is oil wet and water wet,the improved recovery value is 11.42% and 24.09%,respectively.When the displacement velocity is 0.0001m/s,0.0003m/s and 0.0005m/s,the improved recovery value is 5.94%,10.61% and 12.73%,respectively.Increasing the viscosity of the displacement fluid,reducing the interfacial tension between the two phases,changing the wettability of the rock wall and increasing the displacement speed can effectively improve the recovery degree of the remaining oil after polymer flooding,but reducing the interfacial tension is the most obvious displacement effect.This conclusion can provide theoretical and technical support for further improving the recovery degree of cluster remaining oil after polymer flooding.