Capillary Behaviors of Miscible Fluids in Porous Media: A Pore-Scale Simulation Study

Capillary behaviors of two phases in porous media are widely investigated by pore-scale simulations. Flow properties of miscible two-phase fluids pose challenges because compositional species in miscible fluids exist in both of two phases. In this work, pore-network modeling is developed to analyze capillary behaviors of miscible fluids. First, the pore-network structure is generated by introducing the Halton sequence and the Delaunay triangulation. Then, we perform the primary drainage to simulate the variation of capillary pressure as a function of saturation under equilibrium conditions. The miscibility details of two-phase fluids are determined by two-phase flash calculations. The effect of representative network sizes on capillary behaviors is analyzed to balance computational demands and interpretability. Our models demonstrate the efficiency and the robustness of the network generation procedure. Finally, our simulation results indicate that the miscibility of fluids significantly influences capillary behaviors, highlighting the necessity of species-specific compositional modeling for miscible two-phase fluids in porous media.