Simulation of CO ₂ –water two‐phase fluid displacement characteristics based on the phase field method

Abstract The two‐phase flow in porous media is affected by multiple factors. In the present study, a two‐dimensional numerical model of porous media was developed using the actual pore structure of the core sample. The phase field method was utilized to simulate the impact of displacement velocity, the water–gas viscosity ratio, and the density ratio on the flow behavior of two‐phase fluids in porous media. The effectiveness of displacement was evaluated by analyzing CO 2 saturation levels. The results indicate that the saturation of CO 2 in porous media increased as the displacement velocity increased. When the displacement velocity exceeded 0.01 m/s, there was a corresponding increase in CO 2 saturation. Conversely, when the displacement velocity was below this threshold, the impact on CO 2 saturation was minimal. An “inflection point,” M 3, was present in the viscosity ratio. When the viscosity of CO 2 is less than 8.937 × 10 −5 Pa·s (viscosity ratio below M 3), variations in the viscosity of CO 2 had little impact on its saturation. Conversely, when the viscosity of CO 2 exceeded 8.937 × 10 −5 Pa·s (viscosity ratio greater than M 3), saturation increased with an increase in the viscosity ratio. In terms of the density ratio, the saturation of CO 2 increased monotonically with an increase in the density ratio. Similarly, increasing density ratios resulted in a monotonic increase in CO 2 saturation, though this trend was less pronounced in numerical simulations. Analysis results of displacement within dead‐end pores using pressure and velocity diagrams reveal eddy currents as contributing factors. Finally, the impact of pore throat structure on the formation of dominant channels was examined.