Pore-scale simulation of the effects of the interfacial viscoelasticity on oil displacement by low-salinity water in porous media

Enhanced oil recovery through low-salinity waterflooding hinges not only on rock–fluid interactions but also on the intricate interaction between the fluids. Adsorption of polar macromolecules of the oil phase onto the oil-brine interface leads to non-isotropic interfacial tension and a complex rheological reaction to deformations. This phenomenon becomes more complicated by the pore structure during two-phase flow in porous media. This paper represents a pioneering effort to model the influence of interfacial viscoelasticity on oil-brine displacement at the pore-scale using computational fluid dynamics simulations. Following model validation with experiments, we delve into the distinct salinity-dependent effects of shear and dilatational properties of the interface in different geometries with different pore-to-throat aspect ratios and at a capillary-dominated flow regime. The findings indicate that shear stresses arising from interfacial viscoelasticity influence the relative movement of the wetting and non-wetting phases within the pores, resulting in the reduction of trapped oil by improving its mobility. It is also found that the dilatational effects stretch the oil phase passing through the throat. This effect provides additional time for the oil to be released, culminating in a reduction in the trapped oil volume by as much as 5%–7%. This is while the interfacial viscous forces tend to hamper oil flow and increase its snap-off. The viscoelastic forces become more pronounced as the aspect ratio (pore-to-throat size) exceeds 2–3. While conventional waterflooding would result in high remaining oil saturation, this phenomenon arising from lowering water salinity proves to be particularly efficient for oil recovery.