WELL CEMENTING AIDS

摘要

The present invention relates to copolymers consisting of (a) 1 - 99% by weight of structural units of the formula (1) (see formula 1) where R1 is hydrogen or methyl, R4 is C1-C22 alkylene, R5 is C1- C22-alkyl or hydrogen, and X is ammonium, lithium, sodium, potassium, an amine or a mixture of these substances, and (b) 99 - 1% by weight of structural units of the formula (2) (see formula 2) where R1 is hydrogen or methyl, R2 and R3, independently of one another, are hydrogen, or C2-C22-alkyl, wherein component b) is not hydrolyzed and the copolymers have been prepared by a solution precipitation polymerization in a nonaqueous solvent or a water-miscible, organic solvent having a low water content which is a precipitant for the copolymer. The invention furthermore relates to a process for cementing subterranean wells using a cement slurry comprising the following components: a) water of various salinity b) cement c) a novel copolymer in a concentration of 0.01 - 5% bwoc, preferably from 0.05 to 0.9% bwoc.