Patent ID: 7556098

Claim:
A process for recovering oil from a subterranean reservoir by injecting an aqueous liquid containing a mixture of amphoteric surfactants, each characterized by the formula: wherein: R 1 is a hydrocarbyl group containing from 8 to 26 carbon atoms, the average of all hydrocarbyl groups having a ratio of Iodine Value to the Molecular Weight of the hydrocarbyl chain of at least 0.15 or R 1 is an alkyl amido group of the following structure R—O—N—CH 2 CH 2 CH 2 Where R═R 1 R 2 and R 3 are each independently a hydrocarbyl group containing from 1 to 8 carbon atoms or an alkoxy group containing from 2 to 10 carbon atoms and having a ratio of carbon atoms to oxygen atoms within the range of 2 to 3, R 4 is an aliphatic group containing from 1 to 6 carbon atoms, and A is a sulfonate group or a carboxylate group; b) optionally one or more alkali, c) optionally one or more thickening agents, d) optionally one or more co-solvents e) an aqueous solvent; and; recovering the oil from one or more production wells.