Influence of wettability in immiscible displacements with lattice Boltzmann method

The role of wettability, often characterized by contact angle (θ), in two-phase immiscible phases displacement is not well understood. In this study, the color gradient lattice Boltzmann method (LBM), capable of maintaining the prescribed θ (from 0° to 180° at intervals of 10°) throughout the numerical simulations, was used to investigate the displacement patterns and displacement efficiency in a 2D porous medium. The capillary numbers (Ca) used were 0.01, 1, and 100, and the viscosity ratios (M) used were 0.1, 1, and 10. At M=10, the saturation (S) had a bilinear relationship with θ, while for M=0.1 and 1, the S-θ relationships were complicated by Ca. A saturation contour in the M-Ca-θ space was proposed to demonstrate the movement of a traditional 2D M-Ca phase diagram with θ increments. The value of S continued to increase after the breakthrough, and the final saturation (0.997) for the hydrophilic condition (θ=10°) was higher than that (0.673) for the hydrophobic condition (θ=170°).