The Micro-flow Mechanism Study On Two-phase Polymer Flooding Considering The Elastic Turbulence

As a non-Newtonian fluid,polymer flooding technology is widely used in oilfields around the world,and viscoelastic effect of polymer solution can effectively enhanced oil recovery.Most researchers have studied the single-phase flow mechanism of polymer flooding in laminar flow state.However,there are few studies in micro flow mechanism of two-phase polymer flooding.In this paper,based on the study of single-phase flow mechanism of polymer flooding in three-dimensional,the study of two-phase micro-flow mechanism of polymer flooding in two and three-dimensional was investigated.The study results provide important theoretical support for the design and screening of polymer flooding system in tertiary oil recovery of oilfield,and simultaneously are benefit to the enrichment of two-phase flow mechanism of viscoelastic polymer solution.The continuity equation,momentum equation and constitutive equation of viscoelastic polymer solution-oil in porous media at three-dimensional was established.The method of VOF was used to trace the two-phase interface.To constitutive equation,the stress tensor was transformed by the log-conformation reformulation method,which improved the calculation of Weissenberg number(We).According to the actual reservoir pore characteristics in Daqing oilfield,the porous media can reflect the characteristics of real rocks.According to the single phase turbulent flow mechanism of three-dimensional viscoelastic polymer solution,combining the characteristic of velocity and turbulent intensity,it was found that the velocity curve of We=3 begins wave.The velocity curve of We=5 had the large range waved,and strongest turbulent(3.3%).To velocity,streamline and stress characteristics,it is found that polymer flooding had turbulence effect,a larger velocity,a higher unstable the streamline,and greater the maximum stress.According to the velocity change of polymer flooding in two-dimensional pore,there were no occurred elastic turbulence effect.From alpha,velocity,streamline and water cut,it was found that the large number of We,the great displacement efficiency.Compared with We=0.1,We=1,We=2 and We=5,the oil displacement efficiency of polymer flooding(We=23)increased 9.7%-35.6%.According to the analysis of the critical conditions for the occurrence of elastic turbulence of two-phase micro flow mechanism of polymer flooding in three-dimensional,the polymer flooding(We=5)occurred elastic turbulence.the polymer flooding(We=10)had higher turbulence intensity,and the displacement efficiency was 18.8%.With the increase of We,the turbulence intensity and the displacement efficiency were gradually reduced.By Comparing stress and pressure,it is found that the maximum stress and pressure of polymer flooding with Elastic turbulence are higher than the maximum stress and pressure of polymer flooding without elastic turbulence,and elastic turbulence polymer flooding had higher value,with stronger elastic turbulent polymer solution had great value of stress and pressure.According to the distribution characteristics of velocity and streamlines,it is found that the turbulence intensity is highest,Polymer flooding had deepest sweep at dead end,and had obviously secondary vortices.The results show that the elastic turbulent polymer flooding can enhance oil recovery.