Enhanced Oil Recovery Potential of Alkyl Alcohol Polyoxyethylene Ether Sulfonate Surfactants in High-Temperature and High-Salinity Reservoirs

Surfactant flooding has been widely applied in high-temperature and high-salinity reservoirs. In this paper, the enhanced oil recovery potential of alkyl alcohol polyoxyethylene ether sulfonate (CEOS) was investigated in a combined study of surface activity, crude oil-water interfacial tension (IFT) reduction, emulsifying property, wettability improvement, and macroscopic oil displacement efficiency. The results illustrated that CEOS had high surface activity and IFT could be reduced to an ultralow level (10(-3) mN/m) at high-temperature and high-salinity conditions. When salinity ranged from 15 x 10(4) to 22.5 x 10(4) mg/L and reservoir permeability was similar to 10 mD, linear CEOS solution could effectively displace crude oil for its favorable IFT reduction ability. Linear CEOS or CEOS with a benzene ring was optimized for their favorable IFT reduction ability or emulsifying ability when reservoir permeability was similar to 50 mD or non-homogeneous. A 0.5 pore volume surfactant flooding and subsequent water flooding could remarkably enhance oil recovery to 16.19-19.38%. All of the results indicated that CEOS has great potential for improving oil recovery in high-temperature and high-salinity oil reservoirs.