Interfacial behaviour, wettability alteration and emulsification characteristics of a novel surfactant: Implications for enhanced oil recovery

The application of surfactants in enhanced oil recovery (EOR) processes aids in reducing interfacial tension at the oil-aqueous interface as well as altering the wetting nature of the reservoir rock. However, most commercial surfactants used in the petroleum industry are expensive. In an attempt to solve this issue, an anionic surfactant was synthesized from coconut oil as an alternative during oil recovery. The synthesized sodium ethyl ester sulfonate (SEES) surfactant was characterized by FT-IR, 1H NMR and TGA analyses. The critical micelle concentration (CMC) values of SEES surfactant were determined at different temperatures by electrical conductivity method. The interfacial tension (IFT) at the oil-aqueous interface was found to reduce to ultra-low magnitudes in the presence of salt. Alkali addition also plays a synergistic role in IFT reduction ability of SEES solutions. Surfactant solutions exhibited good salt tolerance levels and long-term thermal stability. SEES surfactant also showed improved wettability alteration property, changing the nature of oil-aged rock from intermediate-wet to water-wet. Synergism in wetting characteristics of SEES solution is achieved by salt addition. Additional recoveries of 20.05% was attained in the presence of 0.80 wt% SEES only, which further increased to 33.49% and 34.79% by the addition of 0.01% and 0.02% PHPA polymer respectively.