Theoretical analysis of microscopic oil displacement mechanism by viscoelastic polymer solution

The microscopic oil displacement mechanism in viscoelastic polymer flooding is theoretically analyzed with mechanical method. The effects of viscoelasticity of polymer solution on such three kinds of residual oil as in pore throat, in sudden expansion pore path, and in dead end are analyzed. Results show that the critical radius of mobile residual oil for viscoelastic polymer solution is larger than that for viscous polymer solution, which makes the oil that is immobile in viscous polymer flooding displaced under the condition of viscoelastic polymer solution. The viscous polymer solution hardly displaces the oil in dead ends. However, when the effect of viscoelasticity is considered, the residual oil in sudden expansion pore paths and dead ends can be partly displaced. A dimensionless parameter is suggested to denote the relative dominance of gravity and capillary pressure. The larger the dimensionless parameter, the more accurate the increment expressions.