Formation fracturing

A method to fracture a subterranean formation comprising the steps of:

• a) providing a fracturing fluid, the fracturing fluid being an aqueous solution having an initial pH greater than about 8 and comprising a polysaccharide, a source of borate in an amount that is effective to crosslink the polysaccharide at a pH of greater than 8, an oxidative breaker, and a precursor that hydrolyses in an amount that is effective to lower the pH of the fracturing fluid after a time period that is greater than about one half hour and less than about two days, wherein the precursor is selected from the group comprising ethylacetate, 2-ethoxyethyl acetate, ethyl acetoacetate, methylbenzoate, ethylformate, methylacetate, and dimethylphthalate;
• b) injecting the fracturing fluid into the formation at a pressure that is effective to fracture the formation and force at least a portion of the fracturing fluid into the fracture;
• and
• c) permitting the precursor to hydrolyze and thereby lowering the pH of the fracturing fluid to a pH that is less than about 8.