Compositions and methods for delayed crosslinking in hydraulic fracturing fluids
View Patent ↗Disclosed herein are compositions and methods for delaying crosslinking in injectable compositions for hydraulic fracturing and related applications. The compositions and methods are effective in injectable compositions comprising or substantially excluding dissolved reactive species. The compositions and methods provide delayed crosslinking at high temperatures and pressures, such as those encountered by hydraulic fracturing compositions injected into subterranean environments. Compositions include injectable solutions comprising a competing agent that is the reaction product of a dialdehyde having 2 to 4 carbon atoms with a non-polymeric cis-hydroxyl compound. Also provided are methods of making and using delayed-crosslinking compositions comprising crosslinker compositions containing zirconium complexes and the competing agents.
1. A method of making an injectable solution, the method comprising:
reacting a dialdehyde having 2 to 4 carbons and a non-polymeric cis-hydroxyl compound in an aqueous solution to form a competing agent solution comprising a competing agent and excluding a borate; and
combining a crosslinkable polymer and the competing agent solution in produced water to form the injectable solution, the produced water containing about 10 ppm to 500 ppm boron as dissolved reactive boron species.
2. The method of claim 1 , further comprising injecting the injectable solution into the subterranean reservoir, and recovering a hydrocarbon from the reservoir.
3. The method of claim 1 , wherein the dialdehyde is glyoxal, the non-polymeric cis-hydroxyl compound is sorbitol, and the crosslinkable polymer is selected from guar gum or carboxymethyl hydroxypropyl guar.
4. The method of claim 1 , wherein the combining the crosslinkable polymer and the competing agent in produced water consists essentially of combining the crosslinkable polymer and the competing agent solution solution in produced water, wherein the injectable solution after the combining has a pH of about 5 to about 7, and wherein the method further comprises adding to the injectable solution having a pH of about 5 to about 7 a pH adjusting agent in an amount sufficient to raise the pH of the injectable solution to about 8.5 to 13.
5. The method of claim 4 , further comprising adding to the injectable solution a source of dissolved reactive boron selected from a sparingly soluble borate, boric acid, borate oxyanion, or a combination thereof.
6. The method of claim 4 , wherein about 30 seconds to 5 minutes after the combining the crosslinkable polymer and the competing agent solution in the produced water, the injectable solution reaches a viscosity of at least about 100 cP at 65° C. when measured at 100 s −1 .
7. The method of claim 1 , wherein the method further comprises:
adjusting the pH of the competing agent solution to maintain a pH of about 6.0 to about 6.5;
combining a zirconium tetraalkoxide and an alkanolamine in a solvent to form a crosslinker composition, wherein the combining is carried out at a temperature between about 15 C and about 46° C. and the molar ratio of zirconium tetraalkoxide to the alkanolamine is about 1:9;
maintaining the crosslinker composition at a temperature of from about 35° C. to about 40° C. for 90 to 150 minutes; and
adding the crosslinker composition to the competing agent solution.
8. The method of claim 7 , wherein about 30 seconds to 5 minutes after combining the crosslinkable polymer and the delayed crosslinking composition in the produced water, the injectable solution reaches a viscosity of from about 100 cP to about 10,000 cP at 163° C. when measured at 100 s −1 .