Displacement of polymer solution on residual oil trapped in dead ends

Abstract

For waterflooding reservoir, oil trapped in pore’s dead ends is hardly flushed out, and usually becomes one typical type of residual oil. The microscopic displacement characteristics of polymer solution with varied viscoelastic property were studied by numerical and experimental method. According to main pore structure characteristics and rheological property of polymer solution through porous media, displacement models for residual oil trapped in dead ends were proposed, and upper-convected Maxwell rheological model was used as polymer solution’s constitutive equation. The flow and stress field was given and displacement characteristic was quantified by introducing a parameter of micro swept coefficient. The calculated and experimental results show that micro swept coefficient rises with the increase of viscoelasticity; for greater viscoelasticity of polymer solution, vortices in the dead end have greater swept volume and displacing force on oil, and consequently entraining the swept oil in time. In addition, micro swept coefficient in dead end is function of the inclination angle (θ) between pore and dead end. The smaller of θ and 180-θ, the flow field of viscoelastic fluid is developed in dead ends more deeply, resulting in more contact with oil and larger swept coefficient.