National Starch and Chemical Corporation

Patricia A Gleason

Chester D Szymanski

Ingrid E Brase

Marie A Piccoline

Cationic emulsion polymers useful as thickening agents in aqueous dense brine solutions are disclosed. The cationic polymers are water-in-oil emulsion polymers of acrylamide or methacrylamide and a cationic monomer. The polymers have an intrinsic viscosity in 1.0 N KCl of at least 1 dl/g and preferably have an acrylamide or methacrylamide to cationic monomer molar ratio of about 60:40 to 95:5.

Cationic acrylamide emulsion polymer brine thickeners

Low and high solids drilling fluids containing high levels (i.e., at least 10,000 ppm) of divalent cations are provided with improved fluid loss control by employing high molecular weight water-in-oil emulsion copolymers of acrylamide and a water soluble salt of acrylic acid. The copolymers, produced by the copolymerization in water-in-oil emulsions form of acrylamide and acrylic acid or the salt thereof in molar ratios of 70:30 to 95:5 are particularly effective in drilling fluids containing high levels of calcium ions.

Fluid loss control agents for drilling fluids containing divalent cations

Dispersants useful in aqueous drilling mud formulations employed in the drilling of subterranean wells where high temperature and high pressure environments are encountered are disclosed. The dispersants, when used in amounts of about 0.1 to 25 ppb provide muds containing colloidal material suspended in an aqueous medium with improved high temperature and high pressure stability. The dispersants are water soluble sulfonated vinyl toluene-maleic anhydride copolymers which have a molar ratio of vinyl toluene to maleic anhydride of about 1:1 to less than about 2:1, a molecular weight of 1,000 to 25,000 and at least about 0.7 sulfonic acid groups per vinyl toluene unit.

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Westfield, NJ, United States of America

Patricia A Gleason