Contrasting phase field method and pairwise force smoothed particle hydrodynamics method in simulating multiphase flow through fracture-vug medium

Strong heterogeneity and anisotropy result in complex flow and relatively low oil recovery in fractured-vuggy reservoirs. In this work, we assess the Cahn-Hilliard phase field method (PFM) and the pairwise force smoothed particle hydrodynamics (PF-SPH) method in modeling 2D multiphase flow through fracture-vug medium, in terms of different capillary numbers, mobility ratios, gravity, and wettability. Comparing the results of numerical simulations and physical experiments, the results of the PF-SPH method are closer to the physical experimental displacement process than those of the PFM, and the PF-SPH method is found to be computationally more efficient and accurate than the PFM. The experimental and numerical results reveal that when the injection velocity, represented via logarithm of the capillary number (LCN), is not greater than −4 (gas phase case) or −2.3 (water phase case) in the fracture-vug medium, the gravitative differentiation of the oil-gas or oil-water is significant, and the oil-gas or oil-water flow is a stable stratified flow. When the injection velocity LCN exceeds −3 (gas phase case) or −1.3 (water phase case) in the vertical section, the gravitative differentiation of the oil-gas or oil-water is not obvious, and the fluid flow pattern appears as an unstable jet flow.