Molecular dynamics study of interfacial properties in CO 2 enhanced oil recovery

Abstract CO 2 enhanced oil recovery (EOR) is a promising technique for carbon capture, utilization and storage (CCUS). Owing to the abundant distribution of nanostructure in unconventional oil reservoirs, the investigation on the interfacial properties of the CO 2 and oil system in nanopores is still lacking as well as the corresponding mechanism of displacement of oil by injecting CO 2 in CO 2 EOR. In this study, we coupled CO 2 and n- decane force fields in molecular dynamics (MD) simulations by modifying Lorentz-Berthelot combination rules to calculate key physical properties of CO 2 + n -decane system more accurately. The phase equilibrium and interfacial properties of CO 2 + n -decane binary system were studied under different pressures. Then we explored the interfacial properties of CO 2 + n -decane mixture in α-quartz nanopores and found that the adsorption of CO 2 is stronger than n -decane, which is beneficial for displacing n- decane from the pore surface and then enhancing oil recovery. An increase in the diffusion of n- decane was observed with the increase of injected CO 2 , while when excess CO 2 was injected, the diffusivity of CO 2 and n- decane in nanopore both decreased. The underlying mechanisms of these phenomena were understood by the structure and diffusive properties in bulk and α-quartz nanopores.