Cleanup additive

A composition for hydraulically fracturing a subterranean formation comprising:

• a. a crosslinked polysaccharide, having polyvalent metal crosslinks;
• and
• b. a controlled solubility compound for releasing a chelating agent for controllably breaking the polyvalent metal crosslink and bonding with the polyvalent metal ion resulting from breaking the crosslink, thereby decreasing the viscosity of the polysaccharide;
• wherein the return of the polysaccharide is increased;
• and
• wherein the controlled solubility compound is selected from the group consisting of calcium oxalate, calcium phosphate, aluminum metaphosphate, sodium zinc potassium polyphosphate glass, and sodium calcium magnesium polyphosphate glass.

A method of fracturing a subterranean formation comprising the steps of:

• a. injecting a composition into the subterranean formation, said composition comprising:
• an aqueous mixture of a hydrated polysaccharide, 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 polyyalent metal ion resulting from breaking the crosslink, thereby decreasing the viscosity of the hydrated polysaccharide;
• b. 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
• c. removing the lower viscosity fluid;
• wherein the controlled solubility compound is selected from the group consisting of calcium oxalate, calcium phosphate, aluminum metaphosphate, sodium zinc potassium polyphosphate glass, and sodium calcium magnesium polyphosphate glass.

A method of fracturing a subterranean formation comprising the steps of:

• a. providing a fracturing fluid formed from a crosslinked polysaccharide, having polyvalent metal crosslinks, and a controlled solubility compound for releasing a chelating agent for controllably breaking the polyyalent metal crosslinks and bonding with the polyvalent metal ion resulting from breaking the crosslink;
• b. injecting the fracturing fluid into the subterranean formation;
• c. 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
• d. removing the lower viscosity fluid;
• wherein the controlled solubility compound is selected from the group consisting of calcium oxalate, calcium phosphate, aluminum metaphosphate, sodium zinc potassium polyphosphate glass, and sodium calcium magnesium polyphosphate glass.

A method of selectively predetermining the elapsed time prior to activating the breaking of a viscous gel to conform to variables in a particular fracturing event, comprising:

• a. selecting a composition based on the variables for the particular fracturing event, said composition comprising:
• an aqueous mixture of a hydrated polysaccharide, 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 resulting from breaking the crosslink, thereby decreasing the viscosity of the hydrated polysaccharide;
• b. injecting the composition into a subterranean formation;
• c. reacting the hydrated polysaccharide with the crosslinking agent to form a viscous gel;
• d. hydraulically fracturing the subterranean formation;
• and
• e. chelating the crosslinking agent with the chelating agent to break the viscous gel;
• wherein the controlled solubility compound is selected from the group consisting of calcium oxalate, calcium phosphate, aluminum metaphosphate, sodium zinc potassium polyphosphate glass, and sodium calcium magnesium polyphosphate glass.