Method for producing crude oil using surfactants based on C16C18-containing alkyl-propoxy surfactants

The invention relates to a method for producing crude oil by means of Winsor type III microemulsion flooding wherein an aqueous surfactant formulation which comprises at least one ionic surfactant of general formula R1-O-(CH2C(CH3)HO)m(CH2CH2O)n-XY- M+is forced through injection wells into a mineral oil deposit and crude oil is removed from the deposit through production wells. The invention also relates to ionic surfactants according to the general formula.