Experimental Evaluation of Carbonated Water Flooding Using Microfluidics and Coreflooding for Simultaneous EOR and...

Carbon capture and storage (CCS) in depleted oil and gas reservoirs offers a sustainable pathway to mitigate greenhouse gas emissions through secure, long-term CO₂ sequestration. Understanding CO₂-brine-oil interactions at the pore and core scales is critical for predicting the fate of injected CO₂ and optimizing storage efficiency. This study presents integrated microfluidic and coreflooding experiments to evaluate carbonated water/brine flooding (CWF) in both model and crude oil systems under varying pressure and salinity conditions. At low pressure (150 psig), CWF showed negligible change in residual oil saturation (S _or) after waterflooding (WF). However, at elevated pressure (700 psig), S _or decreased by approximately 12-15%, demonstrating enhanced oil recovery (EOR) potential. CO₂ flooding further reduced residual oil saturation at both low and high pressures. Interfacial tension (IFT) measurements revealed a linear decrease with increasing pressure and a linear increase with salinity for CO₂-saturated brine-oil systems, whereas produced water-crude oil systems exhibited no significant pressure dependence. Coreflooding experiments confirmed that carbonated water injection enhances oil recovery with increasing pressure, and low-salinity systems outperform high-salinity counterparts. At low pressure (150 psig), increasing salinity reduced the total solubility trapping of CO₂ in both brine and oil. In contrast, at high pressure (700 psig), increasing salinity enhanced total solubility trapping, a trend with significant implications for storage capacity estimates in hydrocarbon-bearing reservoirs. These findings elucidate the interdependence of CO₂-EOR driven by oil swelling, viscosity reduction, and IFT reduction, and CO₂ storage through solubility trapping, offering practical insights to optimize CCS and carbonated water injection strategies in hydrocarbon-bearing reservoirs.