Patent ID: 8853136

Claim:
A process for mineral oil production by surfactant flooding comprising forcing an aqueous surfactant formulation comprising at least one anionic surfactant and at least one further surfactant through at least one injection well into a mineral oil deposit and producing mineral oil by removing the mineral oil from the deposit through at least one production well, wherein the aqueous surfactant formulation comprises (A) at least one surfactant (A) of the general formula R 1 —O—(CH 2 —CH—(CH 3 )O) x —(CH 2 —CH 2 O) y —SO 3 M, in which R 1 is a straight-chain or branched aliphatic and/or aromatic hydrocarbon radical having 8 to 32 carbon atoms, M is H + and/or a k-valent counterion 1/k Y k+ , x is a number from 4 to 30, and y is a number from 0 to 30, and the sum x +y is ≦50, the surfactant (A) being prepared by sulfation of the alkoxylated alcohol R 1 —O—(CH 2 —CH—(CH 3 )O) x —(CH 2 —CH 2 O) y —H, with the proviso that the alkoxylated alcohol is prepared by alkoxylation of an alcohol R 1 —OH using double metal cyanide catalysts or double hydroxide clays, 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 aqueous surfactant formulation.