Well treatment fluid compositions and methods of use that include a delayed release percarbonate formulation

Abstract

A well treatment fluid and method of use includes water, at least one hydratable polymer, an optional crosslinking agent, and a delayed release percarbonate formulation effective to reduce initial viscosity of the fluid after a period of time. Also disclosed are processes for fracturing a subterranean formation.

1 . A process for fracturing a subterranean formation comprising:
 injecting under pressure an aqueous hydraulic fluid having a first viscosity into a well bore, wherein the aqueous hydraulic fluid comprises water; at least one at least one hydratable polymer; and sodium percarbonate granules having a delayed release coating of an inorganic material;   forming fractures in the subterranean formation with the hydraulic fluid at the first viscosity and dissolving the delayed release coating to expose the sodium percarbonate to the water after a period of time;   reacting the sodium percarbonate with the at least one hydratable polymer to decrease the first viscosity to a second viscosity; and   recovering at least a portion of the hydraulic fluid having the second viscosity.   
     
     
         2 . The process for fracturing the subterranean formation of  claim 1 , wherein the aqueous hydraulic fluid further comprises a crosslinker for adjusting the first viscosity of the fluid. 
     
     
         3 . The process for fracturing the subterranean formation of  claim 1 , wherein the inorganic material is an alkali metal silicate. 
     
     
         4 . The process for fracturing the subterranean formation of  claim 1 , further comprising adding a proppant to the hydraulic fluid prior to injecting under pressure and in an amount effective to prevent the fractures from closing. 
     
     
         5 . The process for fracturing the subterranean formation of  claim 1 , wherein the at least one hydratable polymer comprises a polysaccharide, a polyvinyl alcohol, a polyacrylamide, and mixtures thereof. 
     
     
         6 . The process for fracturing the subterranean formation of  claim 1 , wherein the at least one hydratable polymer is a guar gum or guar gum derivative. 
     
     
         7 . The process for fracturing the subterranean formation of  claim 1 , wherein dissolving the delayed release coating to expose the sodium percarbonate to the water after the period of time comprises configuring the delayed release coating with a dissolution rate at up to about 3 hours at a neutral pH and about room temperature. 
     
     
         8 . The process for fracturing the subterranean formation of  claim 1 , wherein the crosslinker comprises a titanate, a borate, a zirconium-containing compound, a dialdehyde, and mixtures thereof. 
     
     
         9 . The process of  claim 3 , wherein the alkali metal silicate is in an amount of 15 to 37 weight percent relative to a total weight of the sodium percarbonate and the alkali metal silicate. 
     
     
         10 . The process for fracturing the subterranean formation of  claim 3 , wherein the alkali metal silicate is in an amount of 22 to 37 weight percent relative to a total weight of the sodium percarbonate and the alkali metal silicate. 
     
     
         11 . The process for fracturing the subterranean formation of  claim 3 , further comprising sodium sulfate intermediate the sodium percarbonate and the alkali metal silicate.