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

TLDR

The authors measured interfacial tension between decane, dodecane, and tetradecane and various surfactant systems, calculated critical micelle concentrations, interfacial areas, and interaction parameters, and related micellar shape via the critical packing parameter to the observed ultralow IFT. Ultralow interfacial tensions (~10⁻³ mN/m) were achieved at surfactant concentrations below 0.05 wt %—and even below 0.01 wt %—when mixtures were used at optimal ratios; branched‑chain surfactants were more effective, mixtures of homologues exhibited strongly negative interaction parameters, and ultralow IFT (<10⁻² mN/m) correlated with a critical packing parameter close to one.

Abstract

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 two homologues with two hydrophobic groups show significant molecular interactions, with both and βM having negative values in the 4−5 range in some cases, with the value more negative than βM. The relationship between micellar shape and ultralow IFT was investigated by calculating the critical packing parameter of the surfactants. It was found that ultralow IFT between the surfactant mixtures and the three hydrocarbons investigated could reach ultralow (<10-2 mN/m) values when the critical packing parameter is very close to 1.