Patent ID: 7541316

Claim:
A thermally stable wellbore treatment fluid comprising salt water, at least one polysaccharide in the range of from about 0.2 to about 1.5 pounds per barrel of fluid and an effective amount of at least one polyacrylamide homopolymer having a molecular weight of from about 20,000 to less than 40,000 to maintain stability of the fluid at a temperature greater than about 250° F., wherein the fluid is substantially free of clay, has a pH in the range of from about 8 to about 10, and has a yield point of greater than about 10 lb/100 ft. 2 when exposed to a temperature in a range of from about 300° F. to about 325° F., wherein the effective amount of the polyacrylamide homopolymer is from about 0.5 lb/bbl to about 10.0 lb/bbl, and wherein the salt water comprises from about 14% to about 24% of an ionic salt by weight of the water.