In the secondary development of shale oil reservoirs, CO2 displacement has emerged as a key technology capable of synergistically enhancing oil recovery and achieving CO2 storage. However, the competitive adsorption and microscale flow mechanisms between CO2 and oil in nanoporous media remain insufficiently understood. This work employs the lattice Boltzmann method, integrating molecular dynamics simulations, and Fickian diffusion theory, to successfully validate and quantitatively characterize the immiscible interfacial tension, miscible flow, and competitive adsorption processes in CO2−oil systems. Furthermore, we investigate the complex CO2 displacement and storage behaviors in nanoporous media. The results indicate that the fluid–fluid interaction parameter governs the phase behavior of CO2−oil systems. When the interaction parameter exceeds a critical threshold, CO2 and oil remain immiscible, exhibiting distinct interfacial tension and capillary number variations. In immiscible CO2 displacement, capillary number significantly impacts displacement efficiency, with higher capillary numbers leading to improved recovery. Conversely, when the interaction parameter falls below the critical value, diffusive mixing occurs, where the Péclet number plays a dominant role in CO2 displacement behavior, correlating with viscosity ratio and CO2 adsorption state. For miscible CO2 displacement, differential adsorption capacities between fluids result in distinct transport mechanisms of CO2 and oil within nanopores. Additionally, the heterogeneity of CO2 adsorption capacity in nanoporous media exerts a more pronounced influence on CO2 storage capacity than on oil recovery. Notably, compared to immiscible displacement, miscible CO2 displacement significantly enhances both oil recovery and CO2 storage capacity.
Liu et al. (2025) studied this question.