Oil recovery by surfactant-alcohol waterflooding

Claim 1

In a method for the recovery of oil from a subterranean oil reservoir penetrated by spaced injection and production systems in which an aqueous fluid is introduced into said reservoir via said injection system to displace oil to said production system, the improvement comprising preceding the aqueous fluid introduction with an oil slug consisting of oil, a preferentially oil-soluble alcohol of limited water solubility having from 5 to 7 carbon atoms and a preferentially oil-soluble anionic surfactant is within the range of 0.2-1.0, said surfactant characterized by one of the formulae ##STR3## wherein the R 1 groups are the same or different and are straight or branched-chain aliphatic groups containing from 8 to 12 carbon atoms, n is 2 or 3, q is at least 2, x is a number within the range of 1 to 20, Ar is phenyl or naphthyl, R 2 is a C 1 to C 4 alkyl group, R 3 is a hydrogen, a hydroxy group or a methyl group, and M is an alkali metal, ammonium, or substituted ammonium ion.