Physicochemical and microemulsion properties of dimeric quaternary ammonium salts with trimethylene spacer for enhanced oil recovery

Dimeric surfactants, also termed as Gemini surfactants, are regarded as organic materials which have two hydrophilic head groups and two hydrophobic groups in the molecules linked together with a spacer. In this study, dimeric surfactants of quaternary ammonium bromide connected with a trimethylene spacer group (m-3-m) have been investigated as potential micellar solutions for enhanced oil recovery. Static surface tension, interfacial tension as well as optimal salinity characterized their physicochemical and microemulsion properties. Using modeled petroleum fluids, the critical micelle concentration (CMC) was found dependent not only of the chemical architecture of the surfactant but also of the composition in the liquid phase. The nature and/or the length of spacer group participates significantly to the spatial rearrangement of the dimeric surfactants which subsequently altered the surface properties. For the same spacer group, an ultralow interfacial tension was achieved. Encouraging oil solubilization was found for surfactants used with an effect pronounced for longer alkyl chain. Furthermore, both the effects and the presence of metallic divalent ions on the phase behavior were discussed.