Predicting Oil Droplet Mobilization in Viscoelastic Fluid

Research has shown that when viscoelastic fluids displace crude oil in porous media, in addition to favorable mobility ratios, the accumulation of elastic stress in the fluid–solid contact areas within pores creates an additional mechanism of action. Their horizontal/vertical elastic stress and elastic repulsive force on the flow walls can drive the detachment of oil droplets and accelerate their migration, resulting in a significantly better displacement effect on residual oil in dead oil zones compared with Newtonian fluids. A numerical study of viscoelastic mechanisms in homogeneous porous media using Fluent UDF found that regardless of the competition between factors such as capillary forces and wettability, the additional viscoelastic response of viscoelastic fluids exhibits excellent displacement capabilities. This enhancement effect stems from the increased polymer stress in the fluid–solid contact areas, forming “pushing” and “pinching” effects, with elasticity and shear thinning acting synergistically. Even with unfavorable mobility ratios, strongly elastic viscoelastic fluids can still suppress the decrease in the viscosity of the displacing fluid through elastic instability, achieving efficient displacement. This research clarifies the dominant role of the elasticity of viscoelastic fluids, providing theoretical support for optimizing polymer flooding strategies and improving the tertiary oil recovery efficiency.