Mobilization of trapped oil droplet in porous media through viscoelasticity

Abstract

Viscoelastic fluids flowing through porous media have been shown to provide improvements in oil displacement efficiency resulting from a favorable mobility ratio. In this study, we demonstrate the existence of an additional mechanism sourced from the buildup of elastic stresses near critical fluid–solid contact regions, which is capable of further displacing trapped oil droplets in porous media. Applying a hybrid lattice Boltzmann multiphase model, the viscoelastic mechanism is numerically explored inside a model porous medium, which involves displacing a trapped nonwetting Newtonian droplet with a surrounding viscoelastic fluid. When compared to the purely Newtonian displacing fluid, the additional viscoelastic response provides a considerable mobility enhancement across a range of competing capillary, wettability, and elastic conditions. It is revealed that the source of mobility improvement in the viscoelastic fluid is attributed to the growth of polymer stresses near the fluid–solid contact regions, which contributes to an additional forcing contribution that generates a “pinch-off” mechanism. Ultimately, this additional contribution is found to depend strongly on the elastic properties of the viscoelastic fluid, rather than its viscous properties. This suggests that the use of viscoelastic fluids has the potential to enhance oil recovery efforts in porous media by providing an additional method beyond a favorable mobility ratio.