Use of anionic dispersion polymers as viscosity modifiers in aqueous drilling fluids

Abstract

An aqueous drilling fluid used in drilling wells through subterranean formations having a pH of between about 7 and about 12 and a viscosity of from about 20 to about 80 sec (Marsch cone) which is prepared by admixing fresh water, brine or seawater with about 0.02 lb to about 2.5 lb per barrel, based on polymer actives, of one or more anionic dispersion polymers, wherein the anionic dispersion polymers are composed of about 2 to about 98 mole percent of one or more anionic monomers and from about 98 to about 2 mole percent of one or more nonionic monomers and wherein the anionic dispersion polymers have a RSV of from about 10 to about 50 dL/g, a method of drilling a well bore through a subterranean formation and a method of viscosifying an aqueous drilling fluid.

Dependencies are inferred from the claim text.