Patent ID: 7825072

Claim:
A method for drilling in a water-sensitive subterranean formation, comprising: providing an aqueous-based drilling fluid comprising: a high molecular weight, about 95-100% non-ionic, polyacrylamide having a molecular weight in the range of about 4 million to about 15 million, and a low molecular weight, about 95-100% non-ionic, polyacrylamide having a molecular weight in the range of about 500,000 to about 2 million, wherein the high molecular weight polyacrylamide and the low molecular weight polyacrylamide are selected from the group of polyacrylamides consisting of homopolymers, copolymers, terpolymers and combinations thereof, wherein the high molecular weight polyacrylamide and the low molecular weight polyacrylamide each have a purity of at least about 95% acrylamido monomer species, and wherein the drilling fluid retards hydration of the water-sensitive formation; and drilling in the subterranean formation with the drilling fluid.