An experimental investigation on the use of saponin as a non-ionic surfactant for chemical enhanced oil recovery (EOR) in sandstone and carbonate oil reservoirs: IFT, wettability alteration, and oil recovery

Abstract

Surfactant flooding, a chemical enhanced oil recovery (EOR) technique, boosts oil production mainly through lowering oil–water interfacial tension (IFT) and altering reservoir rock wettability. In the current study, the performance of pure saponin, a non-ionic surfactant, was evaluated for EOR in sandstone and carbonate reservoirs. The performance evaluation experiments were IFT by pendant drop method, wettability through the use of sessile drop technique, and core flood to discover the oil recovery improvement. According to IFT experiments, the surfactant had a critical micelle concentration (CMC) of 5g/L, and which it decreased the oil–water IFT by 66.98% at CMC, for the system free from salt. Moreover, after increasing the salinity by sodium chloride up to 100g/L, it not only was salt-tolerant but also lowered oil–water IFT up to 77.31%. Depending on salt concentration, the surfactant decreased the sessile drop contact angle by 4.49–27.84° and 5.62–16.98° for the sandstone and carbonate slices, respectively. From the core flood experiments, the oil recovery was improved by 8.4% and 6.23% for the surfactant flooding in the sandstone and carbonate cores, respectively. All in all, the non-ionic surfactant saponin performed best in improving oil recovery from both sandstone and carbonate reservoirs.