Simulation of CO2-water two-phase fluid displacement characteristics based on the phase field method

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 CO2 saturation levels. The results indicate that the saturation of CO2 in porous media increased as the displacement velocity increased. When the displacement velocity exceeded 0.01 m/s, there was a corresponding increase in CO2 saturation. Conversely, when the displacement velocity was below this threshold, the impact on CO2 saturation was minimal. An "inflection point," M3, was present in the viscosity ratio. When the viscosity of CO2 is less than 8.937 x 10(-5 )Pa<middle dot>s (viscosity ratio below M3), variations in the viscosity of CO2 had little impact on its saturation. Conversely, when the viscosity of CO2 exceeded 8.937 x 10(-5 )Pa<middle dot>s (viscosity ratio greater than M3), saturation increased with an increase in the viscosity ratio. In terms of the density ratio, the saturation of CO2 increased monotonically with an increase in the density ratio. Similarly, increasing density ratios resulted in a monotonic increase in CO2 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.