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 employing in all or part of said aqueous fluid the following: (a) a mixture of sulfobetaine of the formula ##STR4## wherein R 1 , R 2 and R 3 are hydrocarbyl groups containing 1 to 20 carbon atoms or said hydrocarbyl groups substituted with a hydroxyl group, and a preferentially oil-soluble aliphatic alcohol; (b) an organic quaternary ammonium compound of the formula (R.sub.5).sub.4 N.sup.+ X.sup.- wherein R 5 is an alkyl group containing 1 to 4 carbon atoms and X is halogen or NO 3 ; and (c) a quaternary ammonium thickening agent of the formula ##STR5## wherein R 1 , R 2 , R 3 and R 4 are hydrocarbyl groups containing 1 to 20 carbon atoms, at least one of which contains 16 to 20 carbon atoms and X is halogen or NO 3 ; wherein: (i) said mixture (a), said organic quaternary ammonium compound (b) and said thickening agent (c) are introduced into said reservoir in a single slug; (ii) the concentration of said sulfobetaine in said slug is from about 0.25 to about 3 weight percent; (iii) the ratio of said sulfobetaine to said alcohol is from 3:1 to 2:1, (iv) the concentration of said thickening agent (c) in said slug is from about 0.1 to about 5 weight percent; and (v) the concentration of said organic quaternary ammonium compound (b) in said slug is from about 0.5 to about 5 weight percent.