Relative permeability model of oil-water flow in nanoporous media considering multi-mechanisms

Abstract

The accurate calculation of relative permeability is of critical importance to clarify the multiphase flow behaviors in nanoporous media. In this paper, the relative permeability model is proposed to investigate the oil-water flow behaviors in water-wetting nanoporous media based on the no-slip Hagen-Poiseuille (HP) equation. The proposed model takes into account the oil-water distribution, slip length, adsorbed water viscosity, viscosity ratio of oil to water and pore size distribution (PSD). The oil-water distribution, slip length and adsorbed water viscosity strongly depend on the wall wettability. The results show that the relative permeability of oil phase increases with an increasing viscosity ratio, and it can be larger than 1 because of the positive slip length caused by ‘lubricating’ effect of water film on oil phase. The relative permeability of oil phase decreases with increase of the contact angle which causes the increasing slip length and decreasing adsorbed water viscosity. As average pore radius and frequency fraction increase, the relative permeability of water phase increases. The reason is that the thickness of water film increases for a specific saturation and then leads to the less resistance by the great adsorbed water viscosity effect. This work focuses on the relative permeability of two-phase flow in water-wetting nanoporous media, which can be used in shale or tight oil production, ground water flow and other aspects of two-phase flow.