STUDY ON THE MECHANISM OF POLYMER SOLUTION WITH VISCO ELASTIC BEHAVIOR INCREASING MICROSCOPIC OIL DISPLACEMENT EFFICIENCY

Abstract

In this paper,the visco elastic characteristics of polyacrylamide solution have been studied experimentally.Based on the forms of residual oil after water flooding in porous media and flowing behavior of polymer solution,the mechanisms of the effect of polymer solution with visco elastic characteristic on each type of residual oil after water flooding had been analyzed and the mechanisms of polymer solution with visco elastic characteristic increasing microscopic oil displacement efficiency were studied.By the analysis of microscopic experiments of percolating flow,relevant relationships between the characteristic parameter describing the visco elastic behavior of polymer solution and displacement efficiency of residual oil in “dead ends”were given.It is shown that the larger the visco elastic behavior of polymer solution,the higher the displacement efficiency of residual oil in “dead ends”.The residual oil can be pulled into “oil threads”by the polyacrylamide solution,and a new type of oil flow channel,i.e.“oil thread”channel,can be formed and residual oil flows downstream through the “oil thread”channel.The probability of forming a steady“oil thread”flow channel in polymer flooding was also analyzed theoretically and proved.The research result indicates that the mechanism of polymer solution microscopically increasing oil recovery is due to the visco elastic characteristic of the polymer solution,the sweeping force acting on the residual oil by the visco elastic polymer solution is larger than that of water.The residual oil was not pushed out by the polymer solution but pulled out by the polymer solution.It is also found that every type of residual oil after water flooding can be decreased by visco elastic polymer solution,and the larger the visco elastic property,the stronger the capability of the polymer solution to “sweep out”the residual oil.