Patent ID: 7655604

Claim:
A process of hydraulic fracturing of a subterranean hydrocarbon reservoir, wherein fracturing is carried out using an aqueous wellbore fluid which is an aqueous solution of a surfactant having the formula: (R 1 —X) n Z, wherein: 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; and wherein: the surfactant reversibly thickens the aqueous solution such that the wellbore fluid is a viscoelastic gel, said gel breaks and undergoes a reduction in viscosity within the reservoir, and surfactant from the broken gel mixes with hydrocarbon in the reservoir.