Patent ID: 8584751

Claim:
A process for mineral oil production in which an aqueous surfactant formulation comprising at least one nonionic surfactant and at least one further surfactant is forced through at least one injection well into a mineral oil deposit and crude oil is removed from the deposit through at least one production well, wherein the surfactant formulation at least comprises (A) at least one surfactant (A) of the general formula R 1 —O—(CH 2 —CH 2 —O) x —H, in which R 1 is a straight-chain or branched aliphatic and/or aromatic hydrocarbon radical having 8 to 32 carbon atoms and x is a number from 11 to 40, and (B) at least one surfactant (B) differing therefrom and of the general formula R 2 —Y, in which R 2 is a straight-chain or branched aliphatic and/or aromatic hydrocarbon radical having 8 to 32 carbon atoms and Y is a hydrophilic group, the weight ratio (A)/(B) being from 10:1 to 1:20, and the proportion of the surfactants (A) and (B) together being at least 50% by weight, based on the amount of all surfactants in the surfactant mixture used; wherein the polydispersity of the surfactants (A) is from 1.04 to 1.2.