Experimental investigation of surface activity, micellization behaviour, and enhanced oil recovery performance of saponin-based green surfactants

In this study, three forms of saponin surfactants extracted from the Camellia sinensis plant (CS1, CS2, and CS3) were investigated. Related experiments were conducted to determine their characteristics and performance in the enhanced oil recovery (EOR) parameters like interfacial tension (IFT) and wettability. The crude plant extract cannot reduce the interfacial tension to suitable values for EOR, although it can create water-wetting. The pure saponin has a better performance, and the IFT in its optimal concentration can reach lower values by adjusting the salinity. In addition to reducing IFT well to around 0.3 mN/m, which is considered suitable for EOR, the modified saponin was stronger in wettability alteration than the other two samples. The crude extract reached its lowest IFT of 7.582 mN/m at 3175 ppm, while the pure and modified saponin achieved minimum interfacial tensions of 1.646 and 0.375 mN/m at 1550 and 1125 ppm, respectively. The surfactants altered the wettability, however, the water-wetting was different, so CS3, CS2, and CS1 had the greatest effect on wettability, respectively. The adsorption of CS1, CS2, and CS3 onto porous media was 26.5%, 12.4%, and 16.1%, respectively. Finally, the flooding of CS1, CS2, and CS3 solutions increased the recovery by 7.6%, 12.6%, and 15.8% OOIP, respectively.