Evaluating the feasibility of using a rapeseed oil-derived anionic polymeric surfactant for enhanced oil recovery from carbonate/sandstone composite reservoirs

This study aims to investigate enhanced oil recovery from carbonate/sandstone composite (CSC) reservoirs using a negative-charged rapeseed oil-based polymeric surfactant. The polymeric surfactant was first synthesized and characterized. Temperature stability and salt tolerance were then measured. The experiments of interfacial tension (IFT), viscosity, contact angle, and injection of chemical slugs into the CSC plugs were performed. Based on the results, the surfactant remained stable at reservoir temperature and salinity up to 90,000 ppm, and increased viscosity to optimal levels at the critical micelle concentration (CMC) of 4000 ppm and higher. At concentrations >= 3000 ppm, it exhibited non-Newtonian behaviour, and the IFT was significantly reduced to 62 x 10-3 mN/m at CMC and 21 x 10-3 mN/m at optimum salinity and alkalinity. It also altered the wettability of the rock, reducing the contact angle to 56.29 degrees at CMC. After injecting the polymeric surfactant into a rock plug, oil recovery increased by 26.5%, and water-cut was minimized to 20%.