Oil based drilling fluids useful having reduced change in high shear viscosity over a wide temperature range

Abstract

An oil-based drilling fluid and a method for maintaining viscosity of an oil-based drilling fluid over a temperature range of about 120° F. to about 40° F. The oil-based drilling fluid comprises a quaternary ammonium ion having a corresponding quaternary ammonium salt having a neat shear strength value less than 6000 lb/100 ft2. The organoclay drilling fluid additive imparts a first high shear viscosity to the oil-based drilling fluid at temperatures of 40° F. or less and imparts a second high shear viscosity to the oil-based drilling fluid at temperatures greater than or equal to 120°, wherein the difference between the first high shear viscosity and the second high shear viscosity is less than 110%. The organoclay drilling fluid additive, further imparts a first low shear viscosity to the oil-based drilling fluid at temperatures of 40° F. or less and imparts a second low shear viscosity to the oil-based drilling fluid at temperatures greater than or equal to 120° F., wherein the difference between the first low shear viscosity and the second low shear viscosity is less than 50%. The quaternary ammonium salt may be selected from dimethyl dicoco ammonium salt; dimethyl dicoco ammonium chloride; dimethyl didecyl ammonium salt; dimethyl didecyl ammonium chloride and combinations thereof.

Dependencies are inferred from the claim text.