Modeling of multiphase flow in low permeability porous media: Effect of wettability and Capillary numbers

Shale oil reservoirs are characterized by dense, extremely low permeability, and poorly developed natural fractures, and hydraulic fracturing technology is often used in extraction to improve recovery. It is significant to clarify the mechanism and influence mechanism of the displacement in complex porous media coupled with fractures and matrix to enhance oil recovery. In this study, based on the lattice Boltzmann method utilizing the fracture-matrix pore coupling model, the authors carried out a study of displacement in organic and inorganic pore space and systematically investigated the influence mechanisms of wettability and Ca on the crude oil recovery rate. It was found that the stronger the wettability of the water phase, the higher the crude oil recovery rate, and the lower the residual oil in the form of adsorbed oil film; and the larger the Capillary numbers, the higher the crude oil recovery rate. Crude oil in organic pore space is more difficult to discharge compared with that in inorganic pore space, and the recovery rate of crude oil in organic pore space can be effectively improved by increasing the driving pressure and enhancing the properties of the water phase (fracturing fluid).