Patent ID: 7196041

Claim:
A wellbore fluid configured for use in hydrocarbon recovery comprising: a surfactant, the surfactant being an alkali metal salt of 2-methyl oleic acid or 2-ethyl oleic acid and having the formula (R 1 —X) n Z, where R 1 is an aliphatic group comprising a C 10 –C 25 principal straight chain bonded at a terminal carbon atom thereof to X, and comprising at least one C 1 –C 6 side chain; X being a charged head group, Z being a counterion, and n being an integer which ensures that the surfactant is charge neutral, wherein: the surfactant is soluble in aqueous and organic fluids; the surfactant is configured to form a viscoelastic gel in aqueous media; and the surfactant has a branched structure to provide for prevention or reduction of emulsion formation when an aqueous solution of the surfactant is contacted with a hydrocarbon.