Synthesis and properties of zwitterionic gemini surfactants for enhancing oil recovery

In this paper, a series of double quaternary ammonium salts zwitterionic gemini surfactants YLZ-0–YLZ-4 has been synthesized for the oilfield of high reservoir temperature, high salinity, and even a low API (crude oil density) proportion, which have all increased the difficulties of oil recovery. The products were characterized by IR, ESI-MS, elemental analysis and melting point tests and their physicochemical properties were tested, including solubility, surface tension, critical micelle concentration (CMC), wettability, interfacial tension, salt tolerance, divalent cations tolerance, emulsification, adsorption and flooding experiment. The CMC of the surfactant YLZ-3 is 0.0178%, and it has the best effect of changing the wettability of the rock surface; Under the condition of high salinity injection water in the oilfield, the interfacial tension of YLZ-3 solution reached an ultra-low value of 0.0053 mN/m at the concentration of 0.1% (wt%). Furthermore, YLZ-3 can enhance oil recovery by 9.48% in laboratory flooding experiment. •A series of new zwitterionic gemini surfactants were synthesized.•The surfactant solutions can greatly change the wettability of the rock surface.•The YLZ-3 surfactant solution can reach an ultra-low interfacial tension.•The YLZ-3 solution is very efficient in EOR under extreme reservoir conditions.