Micellization thermodynamics, interfacial behavior, salt-resistance and wettability alteration of gemini hybrid fluorinated surfactant

A new Gemini hybrid surfactant DFCS was prepared to improve salt resistance and interface activity of fluorinated surfactants. This surfactant was expected to be used as a cleanup additive in fracturing and an active agent in water flooding for shale and superlow-permeability sandstone reservoirs. At high salinities, it displayed lower interface tensions than current fluorinated surfactants as well as the obvious non-wettability of water on glass, and the modified natural sandstone surface using DFCS was close to intermediately wetting for the water and oil phases. Also, DFCS exhibited good temperature resistance, and the surface and interface tensions reduced markedly with the temperature below 70 ℃ in water and brine. For DFCS, the molecular area was large, e.g. A CMC = 129.61 Å 2 at 30 °C; the micelle formation was entropy-driven, and the spontaneity was stronger than that of reported hybrid surfactants with single −SO 3 − ion. The TEM observation showed that the diameters of mono-molecules and micelles were respectively 3–5 and 20–30 nm for 1.9 g/L (CMC) DFCS in water. It was found by the UV data that the non-polarity in micellar micro-domains was visibly weaker for Gemini hybrid surfactants in comparison to hydrocarbon surfactants and that salt hardly influenced the sizes of their micelles, resulting in good salt resistance.