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Abstract

According to the present invention, a composition and method for hydraulically fracturing a subterranean formation is provided. The composition comprises an aqueous mixture of a hydrated polysaccharide, preferably a galactomannan gum, the hydrated polysaccharide having a plurality of bonding sites; a crosslinking agent for crosslinking the hydrated polysaccharide at the bonding sites at the conditions of the subterranean formation with a polyvalent metal ion to form a polyvalent metal crosslink, thereby increasing the viscosity of the hydrated polysaccharide; and a controlled solubility compound for releasing a chelating agent for controllably breaking the polyvalent metal crosslink and bonding with the polyvalent metal ion released by breaking the crosslink, thereby decreasing the viscosity of the hydrated polysaccharide. The method comprises the steps of injecting the above-described composition into the subterranean formation at fracturing pressures; allowing the controlled solubility compound to begin breaking the polyvalent metal crosslink, thereby reducing the viscosity of the hydrated polysaccharide and yielding a lower viscosity fluid; and removing the lower viscosity fluid from the subterranean formation.

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First Claim