Alkaline persulfate for low-temperature breaking of multi-chain polymer viscosified fluid

Abstract

A persulfate compound activated by a strong base is used for low-temperature breaking of fluids viscosified with a multi-chain polysaccharide. The breaker system can be used in an oilfield or pipeline application where a multi-chain polysaccharide may be used in a fluid.

What is claimed is: 
     
         1 . A method for breaking a fluid having an apparent viscosity greater than 5 cP, wherein the fluid comprises a water-soluble multi-chain polysaccharide in water, wherein the multi-chain polysaccharide is selected from the group consisting of: a xanthan, a diutan, and any derivative thereof, the method comprising the step of contacting the fluid with:
 (i) one or more water-soluble persulfates; and   (ii) one or more strong bases;   wherein the step of contacting is at one or more temperatures less than 100° F.   
     
     
         2 . The method according to  claim 1 , wherein the water is a brine. 
     
     
         3 . The method according to  claim 1 , wherein the step of contacting does not dilute the fluid more than 10 percent by volume. 
     
     
         4 . The method according to  claim 1 , wherein the fluid having an apparent viscosity greater than 5 cP is selected from the group consisting of: a flow-back fluid, an unused well fluid, a push pill, a pipeline cleaning fluid, and any combination thereof. 
     
     
         5 . The method according to  claim 1 , wherein the multi-chain polysaccharide is in at least a sufficient concentration in the water such that the fluid has a viscosity greater than 5 cP. 
     
     
         6 . The method according to  claim 1 , wherein the multi-chain polysaccharide is xanthan. 
     
     
         7 . The method according to  claim 1 , wherein the one or more persulfates are in a weight ratio of at least 0.5 to 1 of the multi-chain polysaccharide in the water of the fluid. 
     
     
         8 . The method according to  claim 1 , wherein the one or more strong bases are in a mole ratio based on hydroxide of at least 0.5 to 1 of the one or more persulfates. 
     
     
         9 . A method of treating a well, the method comprising the steps of:
 (a) forming a treatment fluid comprising:
 (i) water; and 
 (ii) one or more multi-chain polysaccharides, wherein the multi-chain polysaccharides are selected from the group consisting of: a xanthan, a diutan, and any derivative thereof, wherein the multi-chain polysaccharides are at least a sufficient concentration in the water such that the treatment fluid has a viscosity of at least 5 cP; 
 (iii) one or more water-soluble persulfates; and 
 (iv) one or more strong bases; and 
   (b) introducing the treatment fluid into the well and directing the treatment fluid to a portion of the well having a design temperature less than 100° F.;   wherein the step of introducing the treatment fluid further comprises introducing above the fracture pressure of the subterranean formation.   
     
     
         10 . The method according to  claim 9 , further comprising the steps of:
 (a) after the step of introducing, allowing the treatment fluid to break in the portion of the well; and then   (b) flowing back from the well.   
     
     
         11 . The method according to  claim 9 , wherein the treatment fluid further comprises proppant or gravel. 
     
     
         12 . The method according to  claim 9 , wherein the step of introducing the treatment fluid further comprises: gravel packing. 
     
     
         13 . The method according to  claim 9 , wherein the water is a brine. 
     
     
         14 . The method according to  claim 9 , wherein the treatment fluid is selected from the group consisting of: a flow-back fluid, an unused well fluid, a push pill, a pipeline cleaning fluid, and any combination thereof. 
     
     
         15 . The method according to  claim 9 , wherein the multi-chain polysaccharide is xanthan. 
     
     
         16 . The method according to  claim 9 , wherein the one or more persulfates are in a weight ratio of at least 0.5 to 1 of the multi-chain polysaccharide in the water of the treatment fluid. 
     
     
         17 . The method according to  claim 9 , wherein the one or more strong bases are in a mole ratio based on hydroxide of at least 0.5 to 1 of the one or more persulfates.