A synergetic binary system of waste cooking oil-derived bio-based surfactants and its interfacial performance for enhanced oil recovery

Bio-based surfactants have garnered significant interest nowadays in wide applications particularly in the oil recovery field owing to their renewable property, outstanding surface/interface activity and eco-friendliness. The ultra-low interfacial tension between crude oil and brine is one of the key parameters for evaluating surfactants used in enhanced oil recovery. In this study, we developed a new binary surfactant system formulated by a bio-based zwitterionic surfactant (POA) and a bio-based nonionic surfactant (SOG), and the binary surfactant system exhibits a strong interfacial activity at a very low surfactant dosage. With the total surfactant concertation in a range of 0.1–3 g/L and the mass ratio of POA to SOG in a range of 5:5–9:1, the interfacial tensions of the binary system between crude oil and simulated formation brine could be significantly reduced to an ultra-low level (∼10⁻³ mN/m), indicating a strong synergistic effect between molecules in the binary system. Meanwhile, with the total surfactant concertation of 0.5 g/L and the mass ratio of POA to SOG of 7:3, the binary system demonstrates ultra-low interfacial tensions (∼10⁻³ mN/m) between crude oil and simulated formation brine at the temperature up to 80 ℃, NaCl up to 75 g/L and Ca²⁺ ions up to 20,000 mg/L, and the emulsification and oil film peeling ability are also improved compared with those of the individual POA and SOG. This study opens a new window for the binary bio-based surfactants and provides insights in designing and optimizing the cost-effective displacement systems for enhanced oil recovery with ensuring environmental sustainability.