Synergistic effects of 2-ethoxyethanol and dissolved CO2 on interfacial tension reduction, wettability alteration, and oil swelling through carbonated water flooding in carbonate-sandstone oil reservoirs

This paper investigates how the efficiency of the chemical carbonated water EOR technique is optimized using the nonionic surfactant 2-ethoxyethanol in CO 2 -rich water solutions. Tests were performed at pressure values of 500–1500 psi, temperature of 25 and 75 °C, and solvent concentration from 2 to 15 vol%. It is shown that 2-ethoxyethanol decreases the interfacial tension (IFT) and increases the oil swelling factor. For instance, when the pressure was 1500 psi, and the volume fraction of solvent in the solution was 15%, the IFT was reduced to 1.495 mN/m, and oil swelling became equal to about 33%. This is evidence of the synergism of interactions between CO 2 and the solvent. The contact angle was altered in favor of wettability alteration due to the oil-to-water contact. The influence of salinity (0–33,000 parts per million) was tested under optimized conditions of 1500 psi, 75 °C, and 15%. The minimum values of interfacial tension (0.84–0.93 mN/m) and contact angle (49°–55°) were obtained when moderate salinity levels were maintained (10,000–15,000 parts per million). Increased salinity levels decreased efficiency due to the ion effect. Overall, the addition of 2-ethoxyethanol enhances CO 2 solubility, promotes hydrophilic wettability, and improves oil mobility, highlighting its potential for efficient carbonated water flooding in reservoir conditions.