An electrolyte-containing aqueous polymer solution with a salt content of >10% to 35% by weight with respect to the total weight of the polymer solution, containing at least one dissolved synthetic copolymer and at least one non-ionic surfactant selected from the group formed by ethoxylated C 10 - C 15 fatty alcohols, with the proviso that the average degree of ethoxylation of said surfactants is 8-10, and the non-ionic surfactant has an HLB of at least 10, wherein the synthetic copolymer has been produced by inverse emulsion polymerisation and the synthetic water-soluble copolymer consists of structural units which are obtained by polymerisation of the monomers: i) an amide of an ethylenically unsaturated carboxylic acid and an ethylenically unsaturated sulphonic acid, as well as their alkali metal salts and/or ammonium salts; ii) an amide of an ethylenically unsaturated carboxylic acid, an ethylenically unsaturated sulphonic acid, as well as their alkali metal salts and/or ammonium salts, and a N-vinylamide, iii) an amide of an ethylenically unsaturated carboxylic acid, an ethylenically unsaturated sulphonic acid, as well as their alkali metal salts and/or ammonium salts, an ethylenically unsaturated carboxylic acid and a N-vinylamide, iv) an amide of an ethylenically unsaturated carboxylic acid, an ethylenically unsaturated sulphonic acid, as well as their alkali metal salts and/or ammonium salts, and an ethylenically unsaturated carboxylic acid, and which is particularly preferably a copolymer which consists of structural units which are derived from: - acrylamide and/or methacrylamide and 2-acrylamido-2-methylpropane-sulphonic acid (AMPS) and/or vinylsulphonic acid; or from - acrylamide and/or methacrylamide, and AMPS and/or vinylsulphonic acid and N-vinylformamide and/or N-vinylpyrrolidone; or from - acrylamide and/or methacrylamide and AMPS and/or vinylsulphonic acid and acrylic acid and/or methacrylic acid; or from - acrylamide and/or methacrylamide and AMPS and/or vinylsulphonic acid and acrylic acid and/or methacrylic acid and N-vinylformamide and/or N-vinylpyrrolidone. i) an amide of an ethylenically unsaturated carboxylic acid and an ethylenically unsaturated sulphonic acid, as well as their alkali metal salts and/or ammonium salts; ii) an amide of an ethylenically unsaturated carboxylic acid, an ethylenically unsaturated sulphonic acid, as well as their alkali metal salts and/or ammonium salts, and a N-vinylamide, iii) an amide of an ethylenically unsaturated carboxylic acid, an ethylenically unsaturated sulphonic acid, as well as their alkali metal salts and/or ammonium salts, an ethylenically unsaturated carboxylic acid and a N-vinylamide, iv) an amide of an ethylenically unsaturated carboxylic acid, an ethylenically unsaturated sulphonic acid, as well as their alkali metal salts and/or ammonium salts, and an ethylenically unsaturated carboxylic acid, and which is particularly preferably a copolymer which consists of structural units which are derived from: - acrylamide and/or methacrylamide and 2-acrylamido-2-methylpropane-sulphonic acid (AMPS) and/or vinylsulphonic acid; or from - acrylamide and/or methacrylamide, and AMPS and/or vinylsulphonic acid and N-vinylformamide and/or N-vinylpyrrolidone; or from - acrylamide and/or methacrylamide and AMPS and/or vinylsulphonic acid and acrylic acid and/or methacrylic acid; or from - acrylamide and/or methacrylamide and AMPS and/or vinylsulphonic acid and acrylic acid and/or methacrylic acid and N-vinylformamide and/or N-vinylpyrrolidone. - acrylamide and/or methacrylamide and 2-acrylamido-2-methylpropane-sulphonic acid (AMPS) and/or vinylsulphonic acid; or from - acrylamide and/or methacrylamide, and AMPS and/or vinylsulphonic acid and N-vinylformamide and/or N-vinylpyrrolidone; or from - acrylamide and/or methacrylamide and AMPS and/or vinylsulphonic acid and acrylic acid and/or methacrylic acid; or from - acrylamide and/or methacrylamide and AMPS and/or vinylsulphonic acid and acrylic acid and/or methacrylic acid and N-vinylformamide and/or N-vinylpyrrolidone.