Patent ID: 8002049

Claim:
A method of treating a well comprising pumping a fluid including an aqueous base, solid particles selected from the list consisting of barite, hematite, ilmenite, calcium carbonate, iron carbonate, galena, manganese tetraoxide, dolomite, zinc oxide, cement and mixtures thereof having an average particle size between about 20 μm and 200 μm, and water-dispersable fibers selected from the list consisting of alkali resistant fiber chopped strands or novoloid fibers having a length between about 10 mm and about 25 mm, at a concentration between above 0.5 and 6 pounds per barrel of fluid, wherein the fluid is pumped as drilling fluid and the water-dispersable fibers form on contact of the wellbore a web that enhances the formation of a filter cake, hence reducing loss of fluid into the formation.