Method of enhancing fracture conductivity

A method of hydraulically fracturing a subterranean formation comprising:

• (a) pumping into either the formation or into a wellbore penetrating the formation a proppant-free gelled and/or crosslinked fluid containing at least one viscosifying polymer and/or viscoelastic surfactant and initiating a fracture therein;
• (b) introducing into the wellbore or formation a proppant laden slurry which contains at least one breaker and a viscosifying polymer and/or viscoelastic surfactant;
• (c) degrading the at least one viscosifying polymer and/or viscoelastic surfactant in the proppant-free fluid with the at least one breaker
• wherein the at least one breaker has greater affinity for the at least one viscosifying polymer and/or viscoelastic surfactant in the proppant-free fluid than the viscosifying polymer and/or viscoelastic surfactant present in the proppant laden slurry.

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 a second viscosifying polymer and/or viscoelastic surfactant;
• and
• (b) degrading the first viscosifying polymer with the breaker
• wherein the breaker has greater affinity for the first viscosifying polymer than the second viscosifying polymer and/or viscoelastic surfactant 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.