Patent ID: 8596367

Claim:
A process for mineral oil production by means of Winsor type III microemulsion flooding, in which an aqueous surfactant formulation comprising at least one ionic surfactant, for the purpose of lowering the interfacial tension between oil and water to <0.1 mN/m, is injected through at least one injection borehole into a mineral oil deposit, and crude oil is withdrawn from the deposit through at least one production borehole, wherein the surfactant formulation comprises at least one surfactant of the general formula R 1 —O—(CH 2 C(CH 3 )HO) m (CH 2 CH 2 O) n —XY − M + where R 1 is an unbranched saturated or unsaturated straight-chain aliphatic hydrocarbon radical having 16 to 18 carbon atoms, n is from 0 to 99, m is from 0 to 99, where the sum of n and m is in the range from 3 to 99, Y − is selected from the group of sulfate groups, sulfonate groups, carboxylate groups and phosphate groups, X is an alkyl or alkylene group having 0 to 10 carbon atoms, and M + is a cation.