Patent ID: 8684080

Claim:
A process for tertiary mineral oil production by means of Winsor type III microemulsion flooding, comprising the steps of (a) injecting through at least one aqueous injection borehole into a mineral oil deposit, a surfactant mixture, for the purpose of lowering the interfacial tension between oil and water to <0.01 mN/m, wherein the mixture comprises at least the following components: (i) one or more polycarboxylate(s) comprising at least 50 mol % of acrylic acid units or methacrylic acid units or maleic acid units or itaconic acid units, or salts thereof, or mixtures thereof, and (ii) one or more anionic or nonionic surfactant(s) or mixtures thereof and (b) withdrawing crude oil from the deposit through at least one production borehole.