Patent ID: 7497262

Claim:
A method of forming a subterranean well, the method comprising drilling the subterranean well with a rotary drill bit and a drilling fluid; said drilling fluid including: an aqueous based continuous phase; an optional shale hydration inhibition agent; and a shale encapsulator having the formula: in which x and y have a value so that the molecular weight of the cation is in the range of about 10,000 to about 200,000 AMU; A is selected from C 1 -C 6 alkyl, C 2 -C 6 ether or C 2 C 6 amide; R, R′ and R″ are independently selectable C 1 -C 3 alkyl; and wherein B − is an anion selected from the group of halogen ion, sulfate ion, nitrate ion, formate ion, citrate ion, acetate ion, methylsulfonate ion, and mixtures of these; and wherein the shale hydration inhibition agent and the shale encapsulator are present in a ratio and are in a sufficient concentrations to reduce the swelling of shale clay encountered during the drilling of the subterranean well.