Effect of the Visco-elasticity of Displacing Fluids on the Relationship of Capillary Number and Displacement Efficiency in Weak Oil-Wet Cores

Abstract

Abstract In the past, the elasticity of the displacing solution was not considered when the influence of capillary number on displacement efficiency was studied. Recent years, the theory that the visco-elasticity of flooding fluid can increase displacement efficiency has been gradually accepted, but the present research level can not quantitatively describe the effect of elasticity on elasticity. In this paper, the first normal-stress difference was used to characterize the elasticity of polymer solutions, the influence of capillary number on displacement efficiency and residual oil saturation after flooding by different visco-elastic polymer solutions is studied through experiments on weak oil-wet artificial homogeneous cores. Also, at the same capillary number, the influence of the visco-elastic property of polymer solutions on displacement efficiency and residual oil saturation is studied. A set of curves of capillary number versus displacement efficiency after flooding by different visco-elastic polymer solutions is obtained. The results show that the capillary number and visco-elasticity both influence the displacement efficiency and residual oil saturation. Under conditions of same capillary number, the higher the visco-elasticity of the polymer solution, the higher the displacement efficiency, the lower the residual oil saturation, the visco-elasticity of polymer solution can significantly increase recover efficiency and lower residual oil saturation.