Patent ID: 8889602

Claim:
A method for stabilizing shales while drilling a wellbore into an earthen formation comprising: circulating an aqueous based wellbore fluid in the wellbore while drilling through shales; wherein the aqueous-based wellbore fluid comprises: a copolymer of acrylamide-type comonomers and from about 5 mole % to about 10 mole % of one or more cationic comonomers, the copolymer having a molecular weight of less than about 1,000,000 daltons wherein the one or more cationic comonomers are selected from at least one of diallyldimethylammonium chloride and diallyldiethylammonium chloride and wherein the acrylamide-type comonomer has the chemical formula: where R 1 is selected from H, and C 1 to C 4 alkyl groups; R 2 is selected from H, C 1 to C 4 alkyl groups, CH 2 CH 2 COCH 3 , —C(CH 3 ) 2 CH 2 COCH 3 , —CH═CH 2 , and —C(CH 3 )═CH 2 ; and R 3 is selected from a group consisting of —CH═CH 2 , and —C(CH 3 )═CH 2 , wherein R 1 and R 2 are not simultaneously H.