Water-soluble or water-swellable polymers as water loss reducers in cement slurries

A method for cementing deep wells using a cement slurry, wherein the cement slurry comprises a water-soluble or water-swellable polymer having a k value of 100 to 300, measured in 0.5% by weight solution in distilled water, containing

• a) 25-35 mol % of one or more recurrent structural units derived from monomers selected from the group consisting of acryloyldimethyltaurate, acryloyl-1,1-dimethyl-2-methyltaurate, acryloyltaurate, and acryloyl-N-methyltaurate,
• b) 3 to 8 mol % of one or more recurrent structural units of the formula (2)
• in which
• R1 is hydrogen, methyl or ethyl,
• X+ is H+, NH4+, Li+, Na+, K+, ½ Ca++, ½ Mg++, ½ Zn++, ⅓ Al+++, organic ammonium ions of the formula [HNR5R6R7]+ where R5, R6 and R7 may each independently be hydrogen, a linear or branched alkyl group having 1 to 22 carbon atoms, a linear or branched, mono- or polyunsaturated alkenyl group having 2 to 22 carbon atoms, a C6-C22-alkylamidopropyl group, a linear monohydroxyalkyl group having 2 to 10 carbon atoms or a linear or branched dihydroxyalkyl group having 3 to 10 carbon atoms, and where at least one of the R5, R6 and R7 radicals is not hydrogen, or mixtures of these ions,
• B is a chemical bond, or a linear or branched alkylene group having 1 to 6 carbon atoms, and
• n is an integer from 0 to 5,
• and
• c) 57 to 72 mol % of one or more recurrent structural units of the formula (3)
• in which
• R1 is hydrogen, methyl or ethyl, and
• R3 and R4 are each independently hydrogen, methyl, ethyl, n-propyl, isopropyl or butyl.