Energy & Fuels, Vol.32, No.8, 8220-8229, 2018
Novel Alkyl-Amine Surfactants for CO2 Emulsion Assisted Enhanced Oil Recovery
Novel CO2-soluble surfactants are designed for generating stable CO2 emulsion/foam at high temperature (110 degrees C) and high salinity (220 g/L NaCl). The novel surfactants only consist of alkyl chains and amine heads without any fluorine, silicon, or poly alkyl-oxide groups and outperform the surfactants in literature regarding the solubility, thermal stability, and emulsifying ability in harsh conditions. 0.2 wt % of the novel surfactants are soluble in 220 g/L NaCl brine at pH <= 8 from 20 to 120 degrees C and are soluble in CO, at high temperature (110 degrees C) and relatively low pressure (91 bar). The surfactants are thermally stable at 110 degrees C and pH = 4 under anaerobic conditions. Strong CO2 emulsion can be readily generated in bulk and in porous media at 25-110 degrees C and 150 bar. Unlike the common surfactants in literature, the performance of the novel surfactants can be profoundly enhanced by salinity and temperature. The strategy for designing these novel molecules and tuning the surfactant formulation for emulsion-assisted CO2 enhanced oil recovery (EOR) is discussed as well.