Inhibitive water-based drilling fluid system and method for drilling sands and other water-sensitive formations

A method for stabilizing a shale formation, said method comprising employing an aqueous-based drilling fluid, said drilling fluid comprising low molecular weight non-ionic polyacrylamide and high molecular weight non-ionic polyacrylamide, wherein said high molecular weight non-ionic polyacrylamide is added in liquid or emulsion form and said low molecular weight polyacrylamide is added in powder form.

A method for stabilizing a shale formation, said method comprising employing an aqueous-based drilling fluid comprising low molecular weight non-ionic polyacrylamide and high molecular weight non-ionic polyacrylamide, and further comprising either one or more long chain alcohols or poly anionic cellulose, or both one or more long chain alcohols and poly anionic cellulose.

An aqueous-based drilling fluid comprising a high-molecular weight nonionic polyacrylamide and a low-molecular weight nonionic polyacrylamide, wherein said high-molecular weight non-ionic polyacrylamide is added in liquid or emulsion form and said low-molecular weight non-ionic polyacrylamide is added in powder form.

An aqueous-based drilling fluid comprising a high-molecular weight nonionic polyacrylamide, a low-molecular weight non-ionic polyacrylamide, one or more long chain alcohols, and poly anionic cellulose.

A method for preventing hydration of a water sensitive formation during drilling a borehole in said formation, said method comprising employing an aqueous based drilling fluid during said drilling wherein said drilling fluid comprises high and low molecular weight non-ionic polyacrylamides and was prepared with liquid or emulsion form of said high molecular weight non-ionic polyacrylamides and powder form of said low molecular weight non-ionic polyacrylamides.

A method for preventing formation of gas hydrates in a borehole, said method comprising using an aqueous fluid comprising a combination of low molecular weight non-ionic polyacrylamide and high molecular weight non-ionic polyacrylamide, and at least one or both of alcohols and salts.

A method of enhancing the flocculation of an aqueous based fluid, said method comprising adding to said fluid high molecular weight non-ionic polyacrylamide, low molecular weight non-ionic polyacrylamide, and at least one or both of a long chain alcohol and poly anionic cellulose.

A method of increasing the rate of penetration during drilling, said method comprising using an aqueous based drilling fluid comprising high molecular weight non-ionic polyacrylamide, low molecular weight non-ionic polyacrylamide, and at least one or both of a long chain alcohol and poly anionic cellulose.

A method for conducting drilling operations using an aqueous based drilling fluid in a subterranean formation containing shales or other water-sensitive zones, said method comprising providing said fluid with a high molecular weight non-ionic polyacrylamide, a low molecular weight non-ionic polyacrylamide, and at least one or both of a long chain alcohol and poly anionic cellulose, in amounts that stabilize said shales or water-sensitive zones while enhancing flocculation of solids in said aqueous fluid.