Synergistic Impact of Low Salinity and Surfactant on Wettability Alteration in Carbonates

Abstract The waterflood recovery is often low in tight carbonate reservoirs, which tend to be heterogeneous and oil-wet/mixed-wet. Wettability alteration is a promising strategy for improving oil recovery in such reservoirs. This study aims to improve oil recovery in such a reservoir in West Texas. The mineralogy is determined by XRD analysis. The zeta potential is measured for the drill cuttings. Contact angles are measured on core trims, and imbibition experiments are conducted to evaluate wettability alteration. The optimum salinity was determined to be produced water diluted 40 times from zeta potential measurements. The synergy between low-salinity water and surfactants yielded more than 40% oil recovery in spontaneous imbibition experiments. The addition of sulfate ions and weak acids improved spontaneous imbibition. The results of core flood tests underscored the efficacy of surfactants in improving oil recovery through wettability alteration after waterflooding. This study highlights the potential of low-salinity and surfactant-assisted flooding to improve oil recovery in limestone reservoirs.