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Abstract

A process for recovering oil by injecting into a subterranean oil-bearing reservoir through one or more injection wells, an aqueous solution containing one or more amphoteric alkyl amido betaine surfactants that form a viscoelastic gel reducing interfacial tension and increasing the viscosity of the injection fluid simultaneously, displacing the solution into the reservoir, and recovering the oil from one or more production wells. These viscoelastic gels are tolerant to electrolytes and multivalent cations. They are shear reversible and adsorbed little onto the reservoir. Their viscosity is reduced when contacting certain hydrocarbons but remains high when contacting water or brine. This allows the fluid to preferentially penetrate the oil-bearing portions of the formation and resulting additional oil recovery. These viscoelastic surfactant gels are particularly suitable for use with reservoirs and brines characterized by medium to high temperatures, higher salinity, higher concentrations of divalent cations, and low formation porosities.

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