An analytical model for water-oil two-phase flow in inorganic nanopores in shale oil reservoirs

The existence of water phase occupies oil flow area and impacts the confined oil flow behavior at the solid substrate in inorganic nanopores of shale oil reservoirs, resulting in a completely different flow pattern when compared with the single oil phase flow. This study proposes an analytical model to describe the water-oil two-phase flow. In this model, water slippage at the solid substrate is considered while oil slip is introduced to calculate the oil movement at the solid-oil boundary in dry conditions. It is proven that the oil flow profiles of both the two-phase model and single-phase model show parabolic shapes, but the oil flow capacity drops when water takes up the flow space and the impact of water is more significant when the pore dimension is smaller than 30 nm. Also, the oil flow velocity at a pore center is found to drop linearly given a larger water saturation in wet conditions. The effects of surface wettability and oil properties on water-oil flow are also discussed. Compared with the existing single-phase models, this model describes oil flow pattern in the wet condition with the incorporation of the influence of nanopore properties, which better predicts the oil transport in actual reservoir conditions. Water-oil relative permeability curves are also obtained to improve oil yield.