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US 5,514,644 AGranted
Polysaccharide containing fluids having enhanced thermal stability
AssigneeTexas United Chemical Company, LLC.
InventorJames W. Dobson
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AssigneeTexas United Chemical Company, LLC.
InventorJames W. Dobson
Estimating the term…
The invention provides (1) a method of increasing the thermal stability of an aqueous polysaccharide-containing fluid by adding thereto magnesia and a thiosulfate salt; (2) a drilling, completion, or workover fluid comprising an aqueous liquid, a water soluble polysaccharide, magnesia, and a thiosulfate salt; and (3) an additive for increasing the thermal stability of an aqueous polysaccharide-containing fluid which comprises magnesia and a thiosulfate salt in a weight ratio of magnesia to thiosulfate salt from about 0.15/1 to about 6.67/1. The preferred magnesia has an activity index less than 100, most preferably less than 50. The preferred thiosulfate salt is sodium thiosulfate. The preferred polysaccharide is selected from the group consisting of xanthan gum, epichlorohydrin crosslinked starch, carboxymethyl cellulose, and mixtures thereof. The preferred aqueous liquid is a saturated sodium chloride solution.
A method of increasing the thermal stability of a fluid comprising a saturated sodium chloride solution and at least one water soluble polysaccharide selected from the group consisting of starch derivatives, biopolymers, and mixtures thereof, dispersed therein which comprises adding to the fluid magnesia and a thiosulfate salt selected from the group consisting of sodium thiosulfate, ammonium thiosulfate, potassium thiosulfate, calcium thiosulfate, magnesium thiosulfate, ferrous thiosulfate, and mixtures thereof, the concentration of the magnesia and the thiosulfate salt being sufficient to synergistically increase the thermal stability of the fluid.
An aqueous fluid selected from the group consisting of drilling fluids, completion fluids, and workover fluids which comprises, a saturated sodium chloride solution, a water soluble polysaccharide selected from the group consisting of starch derivatives, biopolymers, and mixtures thereof, magnesia and a thiosulfate salt, wherein the concentration of both the magnesia and thiosulfate salt are from about 1.5 to about 10 pounds per 42 gallon barrel.
An additive for increasing the thermal stability of an aqueous fluid comprising a saturated sodium chloride solution and a water soluble polysaccharide selected from the group consisting of starch derivatives, biopolymers, and mixtures thereof, which comprises magnesia and a thiosulfate salt selected from the group consisting of sodium thiosulfate, ammonium thiosulfate, potassium thiosulfate, calcium thiosulfate, magnesium thiosulfate, ferrous thiosulfate, and mixtures thereof, wherein the weight ratio of magnesia to thiosulfate salt is from about 0.8/1 to about 6.67/1.
Dependencies are inferred from the claim text.