Patent ID: 8408305

Claim:
A method of hydraulically fracturing a subterranean formation comprising: (a) pumping into the formation at least two stages wherein a first stage is a proppant-free fluid and a second stage is a proppant laden slurry and further wherein one of the stages contains a first viscosifying polymer and a crosslinking agent and the other stage contains a breaker and optionally a second viscosifying polymer, viscoelastic surfactant and/or friction reduction agent; and (b) degrading the first viscosifying polymer with the breaker wherein the breaker has greater affinity for the first viscosifying polymer than the optional second viscosifying polymer, viscoelastic surfactant and/or friction reduction agent which may be present in the stage containing the breaker; and further wherein (i) the first viscosifying polymer is selected from the group consisting of cellulose, cellulose derivatives, starch, starch derivatives, xanthan, derivatized xanthan and mixtures thereof; and (ii) the crosslinking agent contains a metal selected from the group consisting of aluminum, antimony, zirconium and titanium.