Pfizer Corporation

Randel E Stong

Stanley W Walinsky

An aqueous drilling fluid suitable for high-temperature use comprising a water base, clay suspended in said base and from about 0.01-25 pounds per barrel total composition of a hydrolyzed terpolymer of maleic anhydride, styrene and a third monomer selected from acrylamide, methacrylamide, acrylic acid or methacrylic acid, the molar ratio of maleic anhydride to styrene to said third monomer being from about 30:10:60 to 50:40:10, and the alkali metal, ammonium and lower aliphatic amine salts thereof, the weight-average molecular weight of said hydrolyzed terpolymer being from about 500-10,000. An improved drilling process wherein such fluids remain flowable at elevated temperatures is also disclosed.

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Gales Ferry, CT, United States of America

Randel E Stong