BORATE CROSSLINKED FRACTURING FLUID VISCOSITY REDUCTION BREAKER MECHANISM AND PRODUCTS

摘要

It has been discovered that borate crosslinked fracturing fluid breakermechanisms are improved by the inclusion of a ration-releasing material. Whencations are released or liberated within the fracturing fluid, they complexwith thehydroxide or carbonate pH buffers used within the borate crosslinkedfracturingfluid, which in turn reduces the pH of the fracturing fluid. Once the pH islowered,viscosity reduction (breaking) occurs by uncrosslinking of the polymer withinthefracturing fluid, and by initiating or increasing activity of an enzymebreaker, ifpresent. In one embodiment, the rations are divalent rations. Two specific,preferredmaterials for releasing divalent rations are calcium lignosulfonate andcalciumchloride, the latter preferably in encapsulated form.