Microscopic Mechanisms of CO₂ Flooding and Sequestration Based on Computational Fluid Dynamics Methods

The CO₂ flooding and sequestration processes in porous media are influenced by various factors, including pore throat structure, stress conditions, CO₂-oil miscibility, and variations in fluid properties. A pore-scale numerical simulation method based on computational fluid dynamics (CFD) is presented to investigate the effects of these microscopic factors on the efficiency of CO₂ flooding and sequestration. Simulation results indicate that fluid convection plays a crucial role in crude oil recovery and carbon sequestration during the initial phase of CO₂ miscible flooding. In the later stages of the process, diffusion emerges as the fundamental mechanism for the mixing of oil components with CO₂, their extraction, and the achievement of CO₂ sequestration within complex pore structures such as dead ends and corners, due to the intricacies of the porous media. This diffusion mechanism can enhance crude oil recovery by up to 18.14%. Furthermore, reductions in fluid density and viscosity significantly increase the concentration gradient of oil/CO₂ components in the primary permeable area, thereby markedly improving the diffusion efficiency of each component and accelerating the overall efficiency of CO₂ flooding and sequestration. The findings provide theoretical support for CO₂ flooding and sequestration processes in practical applications.