Process of hydraulic fracturing using a viscoelastic wellbore fluid

1n1 1025 16 Hydraulic fracturing of a subterranean hydrocarbon reservoir is carried out using an aqueous wellbore fluid which is an aqueous solution of a surfactant which has the formula (R-X)Z, where Ris an aliphatic group comprising a C-Cprincipal straight chain bonded at a terminal carbon atom thereof to X, and comprising at least one C-Cside chain. X is a charged head group, Z is a counterion, and n is an integer which ensures that the surfactant is charge neutral. The surfactant reversibly thickens the aqueous solution such that the wellbore fluid is a viscoelastic gel. The viscoelastic gel breaks and undergoes a reduction in viscosity within the reservoir and surfactant from the broken gel mixes with hydrocarbon in the reservoir.