Shale Pore-Scale Numerical Simulation of Oil-Water Two-Phase Flow

The pore structure of shale is complex, including many micro-nano pores. The occurrence and flow patterns of fluids in the pore space of shale are also more complex. It is crucial to clarify the fluid flow patterns and influencing factors in order to improve shale oil recovery. First, based on CT images of shale cores from DY depression, and considering the natural microfracture development of shale reservoirs in this area, a 2D porous medium model of shale containing microfractures was established. In order to understand the imbibition and displacement process of water and oil from a microscopic perspective, a two-phase flow mathematical model was established using the phase-field method to study the effects of wettability, oil viscosity, and displacement pressure on the distribution of residual oil and recovery degree. The results indicated that wettability determines whether capillary force is the driving force of imbibition or resistance, so as the contact angle increases, oil recovery decreases. Because oil viscosity affects the viscous resistance of oil phase flow, as oil viscosity increases, oil recovery decreases. The higher the displacement pressure, the more oil will be discharged from the pores, thereby improving oil recovery. In summary, this study demonstrated the flow mechanism during imbibition and displacement at the pore-scale, which provides a theoretical basis for the development of shale oil.