Multi-scale flow patterns during immiscible displacement of oil by water in a layer-inhomogeneous porous media

This paper presents the results of numerical study of the relationship between micro-and macroscale flows during immiscible displacement in a two-layer porous medium. A feature of the proposed approach is the allowance for large-scale capillarity induced flow due to curvature of the displacement front in macro-inhomogeneous porous medium. The physical mechanisms determining the development of viscous instability in a layer-inhomogeneous porous medium are considered, the methods for suppressing viscous fingers formation based on the stabilization of the displacement front due the action of capillary forces are proposed.

Pore Scale Study of the Effects of Wettability Alteration on Enhanced Oil Recovery

Drainage displacement at unfavorable viscosity ratios is often encountered in oil recovery process, which significantly limits the oil recovery. Surfactants have been extensively used as wettability modifier to improve the hydrocarbon recovery from rock matrix by imbibition, but little attention has been paid to the use of surfactant-aided wettability alteration to suppress fingering during displacement. In this study, we investigate the surfactant-aided immiscible displacement in oil-wet microfluidic chips. We find that the change of advancing contact angle by surfactant is velocity dependent and stable displacement can be achieved at low velocity when surfactant solution is used at the injection fluid. In comparison, fingering occurs at all capillary numbers for water injection, resulting in low oil recovery. Besides, the generation of oil ganglion during waterflooding and surfactant flooding exhibits completely different characteristics. Our study reveals the pore-scale mechanism of surfactant-aided wettability on the immiscible displacement, which is important for highly efficient oil recovery.