Research on the Hydrodynamics of the Mechanism of Viscous-Elastic Fluids Displacing Residual Oil Droplets in Micro Pores

Abstract

In order to analyze the microscopic stress field acting on residual oil droplets in micro pores, calculate its deformation, and explore the hydrodynamic mechanism of viscous-elastic fluids displacing oil droplets, the viscous-elastic fluid flow equations in micro pores are established by choosing the Upper Convected Maxwell constitutive equation; the numerical solutions of the flow field are obtained by volume control and Alternate Direction Implicit methods. From the above, the velocity field and microscopic stress field; the forces acting on residual oil droplets; the deformations of residual oil droplets by various viscous-elastic displacing fluids and at various Wiesenberg numbers are calculated and analyzed. The result demonstrated that both the normal stress and horizontal force acting on the residual oil droplets by viscous-elastic fluids are much larger compared to that of inelastic fluid; the distribution of normal stress changes abruptly; under the condition of the same pressure gradient in the system under investigation, the ratio of the horizontal forces acting on the residual oil droplets by different displacing fluids (which are water, a power-law fluid with a power law index of 0.6 and a viscous-elastic fluid with a Wiesenberger Number of 0.3 respectively) is about 1:8:20, which means that under the above conditions, the driving force on a oil droplet is 20 times higher for a viscous-elastic fluid compared to that of a Newtonian Fluid. This force must be considered when studying the mechanism of isolated oil droplets mobilization. Furthermore, the viscous-elastic fluids will cause the residual oil droplet to deform much more significantly, beneficial to the mobilization of residual oil droplets. The above results are very beneficial to understanding the mechanism of the mobilization of residual oil droplets by viscous-elastic fluids; the conclusions are supportive of the mechanism that viscous-elastic driving fluids can increase the Displacement Efficiency. This should be of help in designing new chemicals and selecting Enhanced Oil Recovery systems.