National Starch and Chemical Corporation

Ingrid E Brase

Patricia A Gleason

The deposition of scale-imparting precipitates in aqueous media containing significant amounts of barium sulfate and other scale forming salts (e.g., calcium carbonate and calcium sulfate) is inhibited and controlled by adding a scale-inhibiting amount of a water-soluble acrylic acid copolymer with up to about 30% by weight of a vinyl sulfonate, with the copolymer having a weight average molecular weight of below about 90,000.

Process for inhibiting scale formation and modifying the crystal

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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E. Windsor, NJ, United States of America

Ingrid E Brase