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Abstract

This polymeric, acrylamide-free water retention agent, intended inter alia for drilling fluids in the high-temperature range and based on vinylic sulfonic acids, may be composed of the two principal components A and B, component A being selected from the group a) consisting of vinylic substituted sulfonic acid of the series 2-acrylamido-2-methylpropanesulfonic acid (AMPS), vinylsulfonic acid, methallylsulfonic acid or styrenesulfonic acid, salts thereof with a valence of at least 1, or mixtures thereof, or b) a divalent salt of homopolymers or copolymers of a vinylic substituted sulfonic acid of the series 2-acrylamido-2-methylpropanesulfonic acid (AMPS), vinylsulfonic acid, methallylsulfonic acid or styrenesultonic acid or mixtures thereof. In the case where component A comprises group a), the polymer further comprises component B) composed of a) from 4.99 to 60 mol % of an unsaturated, polybasic, cis-positioned carboxylic acid monomer and b) from 0.01 to 10 mol % of a monomer having a polyalkylene oxide side chain which contains from 1 to 120 repeating units of the alkylene oxide. The claimed composition, in particular in the form of a copolymer having a molar weight of between 10 000 and 3 000 000 g/mol, is used preferably in drilling fluids and as an additive to cement slurries with electrolyte contents of between 50 ppm and saturation at temperatures above 200.degree. F. and/or in the presence of formates.

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First Claim