Fracturing subterranean formation

Claim 1

A method of fracturing a subterranean formation penetrated by a borehole which comprises: a. providing a flowing stream of an aqueous fluid; b. providing a compound in said fluid for releasing borate ions into said fluid prior to or substantially concurrently with injection of the components recited in clause (c); c. substantially continuously formulating a fracturing fluid by substantially continuously injecting into the flowing aqueous stream: 1. a galactomannan gum, 2. a buffer which produces an initial acidic pH in the fluid, and 3. a delayed action basic compound to neutralize said buffer and produce a basic pH in said fluid after a period of time sufficient both to permit introduction of said fluid into the borehole while still at an acidic pH to permit said gum to hydrate, yet within a time period such that said hydrated gum is crosslinked with said borate ion prior to reaching said formation, the amounts of said borate ion, gum, buffer, and basic compound employed being sufficient to form a fracturing fluid; d. substantially as said fracturing fluid is formulated and while the pH of the fluid is still acidic, introducing a quantity of said fracturing fluid into the borehole sufficient for fracturing the formation; e. permitting the pH of the introduced fluid to change from acidic to basic before said introduced fluid is brought into contact with the formation, thereby effecting borate crosslinking of the gum; and f. contacting the formation with said fluid containing crosslinked gum, under sufficient pressure to fracture the formation.

Claim 2

A method of fracturing a subterranean formation penetrated by a borehole which comprises: a. providing a flowing stream of an aqueous fluid; b. providing a compound in said fluid for releasing borate ions into said fluid prior to or substantially concurrently with injection of the components recited in clause (c); c. substantially continuously formulating a fracturing fluid by substantially continuously injecting into the flowing aqueous stream: 1. a galactomannan gum, 2. a buffer which produces an initial acidic pH in the fluid, and 3. a delayed action basic compound to neutralize said buffer and produce a basic pH in said fluid after a period of time sufficient both to permit introduction of said fluid into the borehole while still at an acidic pH to permit said gum to hydrate, yet within a time period such that said hydrated gum is crosslinked with said borate ion prior to reaching said formation, the amounts of said borate ion, gum, buffer, and basic compound employed being sufficient to form a fracturing fluid; d. substantially as said fracturing fluid is formulated and while the pH of the fluid is still acidic, introducing a quantity of said fracturing fluid into the borehole sufficient for fracturing the formation; e. permitting the pH of the introduced fluid to change from acidic to basic before said introduced fluid is brought into contact with the formation, thereby effecting borate crosslinking of the gum; and f. contacting the formation with said fluid containing crosslinked gum, under sufficient pressure to fracture the formation.