| 摘要 |
It has been discovered that borate crosslinked fracturing fluid breaker mechanisms are improved by the inclusion of a cation-releasing material. Whe n cations are released or liberated within the fracturing fluid, they complex with the hydroxide or carbonate pH buffers used within the borate crosslinked fracturing fluid, which in turn reduces the pH of the fracturing fluid. Once the pH is lowered, viscosity reduction (breaking) occurs by uncrosslinking of the polymer withi n the fracturing fluid, and by initiating or increasing activity of an enzyme breaker, if present. In one embodiment, the cations are divalent cations. Two specific, pre- ferred materials for releasing divalent cations are calcium lignosulfonate a nd cal- cium chloride, the latter preferably in encapsulated form.
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