Hydrolyzed co-polymers of n-vinylamide and acrylamide for use as waterloss control additives in drilling mud

Abstract From the Canadian patent

Aqueous, clay-based drilling mud compositions are improved with respect to waterloss control by the addition of a hydrolyzed copolymer of acrylamide and an N-vinylamide. The copolymer, which is effective over a broad range of molecular weights, contains at least 5 mol percent of the N-vinylamide monomer moiety of which at least 5 mol percent is hydrolyzed to vinylamide units. Well drilling is improved by circulating through the bore hole a drilling mud containing this waterloss control additive.