Oil-water interfacial tension, wettability alteration and foaming studies of natural surfactant extracted from Vernonia Amygdalina

Surfactant flooding is an enhanced oil recovery (EOR) method for recovering residual oil in the reservoir through mechanism of interfacial tension (IFT) reduction and wettability alteration. Due to toxicity and high cost associated with conventional surfactants, recent research has focussed on developing low-cost and environmentally benign surfactants. Herein, a low-cost green surfactant is extracted from Vernonia Amygdalina (VA) and appraised for EOR applications. The extracted surfactant was characterized using Fourier Transform Infrared (FTIR) and High-Pressure Liquid Chromatography (HPLC). The IFT of the synthesized surfactant at the oil-water interface was determined using Kruss tensiometer. Additionally, the foam stability of the synthesized surfactant was examined. Moreover, the wettability of the saponin based natural surfactant (SBNS) at the rock-fluid interface was analysed using Dataphysics drop shape analyser. Experimental result revealed that SBNS (1 wt% concentration) stabilized foam for longer periods with half-life of 1100 min. Furthermore, the synthesized surfactant was effective in lowering the IFT of oil-water interface from 18 mN/m to 0.97 mN/m. Finally, SBNS altered the wettability of sandstone cores to water-wetting condition by reducing the contact angle from 118.5 ° to 45.7 °. Overall, SBNS exhibit excellent properties desirable for EOR and thereby recommended as supplementary alternative to conventional surfactants.