| 摘要 |
A complexor and method of use are shown for providing controlled delay of the cross-linking reaction in an aqueous well fracturing fluid. A base fluid is first prepared by blending together an aqueous fluid and a hydratable polymer which is capable of gelling in the presence of borate ions. The complexor is prepared by mixing a cross-linking additive capable of furnishing borate ions in solution with a delay additive. The delay additive is effective, within a selected pH range, to chemically bond with both boric acid and the borate ions produced by the cross-linking additive to thereby limit the number of borate ions initially available in solution for subsequent cross-linking of the hydratable polysaccharide. The subsequent rate of cross-linking of the polysaccharide can be controlled by adjusting the pH of the complexor solution.
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