Effect of the Viscoelasticity of Flooding System on Oil Displacement Efficiency

In the past, with regard to the study of polymer flooding, the role played by elasticity is ignored. It is generally agreed that the ratio of macroscopic pressure gradient to interfacial tension determines the oil displacement efficiency. But the new study found that when the macro-pressure gradient and interfacial tension are the same, the more oil displacement efficiency is obtained by viscoelastic polymer flooding. In this paper, the influence of viscoelasticity of flooding system on oil displacement efficiency and residual oil saturation after indoor physical simulation flooding experiment was studied through intermediate wettability homogeneous artificial core. At the same time, under the conditions of the same capillary numbers, the influence of the different visco-elastic polymer solutions on oil displacement efficiency and irreducible oil saturation was also studied. And a set of curves of capillary number versus displacement efficiency after flooding by different visco-elastic polymer solutions is obtained. The study shows that capillary number has a certain effect on the displacement efficiency of viscoelastic fluid and irreducible oil saturation, and there is a regular pattern on different visco-elastic polymer solution. So, under the conditions of the same elasticity of polymer solution, the higher capillary number, the higher displacement efficiency, the lower irreducible 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.