Pore-Scale Analysis of Key Factors in Low Salinity Carbonated Water Flooding for Enhanced Oil Recovery

Low salinity carbonated water flooding (LSCWF) integrates the advantages of low salinity water flooding and carbonated water flooding in enhancing oil recovery (EOR). It also possesses the potential for CO2 geological storage as a promising pathway of CCUS technology. To investigate the key factors influencing its microscopic oil displacement mechanism, this study builds upon prior pore-scale numerical simulation work, focusing on analyzing the effects of injection velocity and oil phase viscosity on LSCWF performance. Results indicate that the influence of injection velocity on recovery factor is non-monotonic, exhibiting a minimum recovery point. Low injection velocities favor sufficient CO2 mass transfer, promoting oil mobilization in regions like blind ends and corners, whereas high velocities rely on increased pressure differentials to expand sweep efficiency and improve recovery. Increasing oil viscosity reduces the recovery factor; however, compared to water flooding (WF), LSCWF maintains a significant enhancement ranging from 14.99% to 32.87% across viscosities of 5–100 mPa·s, demonstrating good adaptability to high-viscosity oils. This study elucidates the influence mechanisms of key parameters on LSCWF development effectiveness from the pore scale, providing a theoretical basis for optimizing and applying this technology.