Ultralow Interfacial Tension for Enhanced Oil Recovery at Very Low Surfactant Concentrations

The interfacial tension (IFT) between alkanes and several individual surfactants and their mixtures has been investigated, using three kinds of alkyl hydrocarbons:  decane, dodecane, and tetradecane. For individual and mixed surfactant systems, critical micelle concentrations and areas per molecule at the hydrocarbon−aqueous solution interface were calculated; for the mixed surfactant systems, , the molecular interaction parameter at the hydrocarbon−aqueous solution interface, and βM, the molecular interaction parameter in mixed micelle formation, were calculated. It was found that IFT in the 10-3 mN/m (ultralow) range can be obtained at surfactant concentrations below 0.05 wt % and even at concentrations below 0.01 wt %, when mixtures of certain surfactants are used at the proper ratio. Surfactants with branched-chain alkyl groups show a much better IFT reduction effectiveness than those with straight-chain alkyl groups. Contrary to what has been observed at the air−aqueous solution surface, mixtures of ...