Viscosity Breaker for Polyacrylamide Friction Reducers

Abstract

A well treating fluid useful in slickwater fracturing processes contains polyacrylamide friction reducer and a viscosity breaker capable of reducing the viscosity of the well treating fluid to about the viscosity of water at ambient temperatures of typical underground formations. The viscosity breaker is selected from the group consisting of hydrogen peroxide, calcium peroxide, magnesium peroxide, and zinc peroxide and is present in an amount above about 0.002% by weight.

1 . A well treating fluid for use in slickwater fracturing comprising:
 water;   a polyacrylamide friction reducer present in an amount of from about 0.005% to about 0.04%; and   a viscosity breaker present in an amount above about 0.002% by weight, wherein the viscosity breaker is a peroxide selected from the group consisting of hydrogen peroxide, calcium peroxide, magnesium peroxide, and zinc peroxide;   whereby the well treating fluid has a viscosity and the viscosity is reduced from an initial viscosity to about the viscosity of water within about 18 hours.   
     
     
         2 . The well treating fluid of  claim 1  wherein the viscosity breaker is hydrogen peroxide. 
     
     
         3 . The well treating fluid of  claim 1  wherein the polyacrylamide is cationic. 
     
     
         4 . The well treating fluid of  claim 1  wherein the water is fresh water. 
     
     
         5 . The well treating fluid of  claim 1  wherein the water is salt water containing less than about 10% salt content. 
     
     
         6 . The well treating fluid of  claim 1  further comprising other additives selected from the group consisting of surfactants, scale inhibitors, microbiocides, and mixtures thereof. 
     
     
         7 . The well treating fluid of  claim 1  wherein the well treating fluid has an initial viscosity below about 3 centipoise at a temperature of about 90° F. 
     
     
         8 . The well treating fluid of  claim 2  wherein:
 the polyacrylamide friction reducer is present in an amount of from about 0.005% to about 0.04% by weight;   the viscosity breaker is present in an amount of from about 0.002% to about 0.02% by weight; and   the well treating fluid has an initial viscosity from about 0.8 to about 5 centipoise at a temperature of about 90° F.   
     
     
         9 . The well treating fluid of  claim 1  wherein the viscosity breaker is an encapsulated peroxide selected from the group consisting of calcium peroxide, magnesium peroxide and zinc peroxide. 
     
     
         10 - 21 . (canceled)