Hydrophobically associating copolymers

A process for enhanced oil recovery comprising utilizing a water-soluble, hydrophobically associating copolymer comprising at least

• (a) 0.1 to 12% by weight of at least one monoethylenically unsaturated, hydrophobically associating monomer (a), and
• (b) 70% to 99.5% by weight of at least one monoethylenically unsaturated hydrophilic monomer (b) different therefrom,
• wherein the quantitative data are based in each case on the total amount of all of the monomers in the copolymer, wherein at least one of the monomers (a) is a monomer of the general formula (I)
• H2C═C(R1)—R4—O—(—CH2—CH(R2)—O—)k—(—CH2—CH(R3)—O—)l—R5 (I)
• wherein the units —(—CH2—CH(R2)—O—)k and +CH2—CH(R3)—O—)l are arranged in block structure in the order shown in formula (I) and the radicals and indices have the following meaning:
• k:
• a number from 10 to 150,
• l:
• a number from 5 to 25,
• R1:
• H or methyl,
• R2:
• independently of one another, H, methyl, or ethyl, with the proviso that at least 50 mol % of the radicals R2 are H,
• R3:
• independently of one another, a hydrocarbon radical having at least 2 carbon atoms or an ether group of the general formula —CH2—O—R2′, wherein R2′ is a hydrocarbon radical having at least 2 carbon atoms,
• R4:
• a single bond or a divalent linking group selected from the group consisting of:
• —CnH2n)—, —O—(Cn′H2n′), and —C(O)—O—(Cn″H2″), wherein n, n′, and n″ is in each case a natural number from 1 to 6, and
• R5:
• H or a hydrocarbon radical having 1 to 30 carbon atoms.
• and further comprising injecting an aqueous formulation of said water-soluble, hydrophobically associating copolymer in a concentration of 0.01 to 5% by weight through at least one injection bore into a mineral oil deposit and removing crude oil from the deposit through at least one production bore,
• wherein said water-soluble, hydrophobically associating copolymer is a copolymer (A1) which comprises at least two different hydrophilic monomers (b), and these are at least
• one neutral hydrophilic monomer (b1), and
• at least one hydrophilic anionic monomer (b2) which comprises at least one acid group selected from the group consisting of —COOH, —SO3H, —PO3H2, and salts thereof.