ADDITIVE FOR REDUCING TORQUE ON A DRILL STRING

摘要

A method of reducing the torque of a drill string used in drilling a subterranean well that includes injecting into the drilling fluid a composition including a base fluid and a polymer coated colloidal solid material. The polymer coated colloidal solid material includes: a solid particle having an weight average particle diameter (d₅₀) of less than ten microns, and a polymeric dispersing agent coated onto the surface of the solid particle during the cominution (i.e. grinding) process utilized to make the colloidal particles. The polymeric dispersing agent may be a water soluble polymer having a molecular weight of at least 2000 Daltons. The solid particulate material may be selected from materials having of specific gravity of at least 2.68 and preferably the solid particulate material may be selected from barium sulfate (barite), calcium carbonate, dolomite, ilmenite, hematite, olivine, siderite, strontium sulfate, combinations and mixtures of these and other similar solids that should be apparent to one of skill in the art.