Chlorine dioxide precursor and methods of using same

Abstract

According to one aspect of the invention, a method of converting an oxy halide salt into a halide dioxide in a reaction zone under certain conditions is provided. More specifically, the method includes generating chlorine dioxide from a stable composition comprising an oxy halide salt by introducing said composition to a reducing agent and minimum temperature within the reaction zone. According to another aspect of the invention, a composition for a stable chlorine dioxide precursor comprising an oxy halide salt is provided.

1 - 46 . (canceled) 
     
     
         47 . An aqueous chlorine dioxide precursor composition comprising 5% to 40% by weight of sodium chlorate and 5% to 20% by weight of citric acid, wherein the composition is stable at a temperature below about 90° F. and wherein the composition reacts to form chlorine dioxide when exposed to a reducing agent in combination with a temperature of about 110° F. or greater. 
     
     
         48 . A treatment fluid comprising a well fluid and an aqueous chlorine dioxide precursor composition, the aqueous chlorine dioxide precursor composition comprising 5% to 40% by weight of a chlorate salt and 5% to 20% by weight of a weak acid. 
     
     
         49 . A method comprising introducing a chlorine dioxide precursor composition into a well fluid to form a treatment fluid, the chlorine dioxide precursor composition being an aqueous solution comprising 5 to 40% by weight of a chlorate salt and 5 to 20% by weight of a weak acid, wherein the composition is stable at a temperature below about 90° F., and wherein the composition reacts to form chlorine dioxide when exposed to a reducing agent in combination with a temperature of about 
     
     
         50 . The method of  claim 49 , wherein the chlorine dioxide precursor composition does not comprise a strong acid. 
     
     
         51 . The method of  claim 49 , wherein the weak acid is citric acid, lactic acid, formic acid, oxalic acid, ethanoic acid, acetic acid, propanoic acid, or a mixture of two or more thereof. 
     
     
         52 . The method of  claim 51 , wherein the weak acid is citric acid. 
     
     
         53 . The method of  claim 51 , wherein the chlorate salt is sodium chlorate. 
     
     
         54 . The method of  claim 53 , wherein the weak acid is citric acid. 
     
     
         55 . The method of  claim 49 , wherein the chlorine dioxide precursor composition further comprises a strong acid at a concentration of 0.1 to 2% by weight, wherein the strong acid is hydrochloric acid, hydrofluoric acid, or a mixture of hydrochloric and hydrofluoric acid. 
     
     
         56 . The method of  claim 49 , wherein the method comprises introducing the chlorine dioxide precursor composition into the well fluid at a concentration of about 100 to 10,000 mg/L. 
     
     
         57 . The method of  claim 49 , wherein the treatment fluid comprises one or more additives selected from the group consisting of a friction reducer, a wetting agent, a polymer, a corrosion inhibitor, sand, a proppant, a biocide, and a breaker. 
     
     
         58 . The method of  claim 49 , further comprising introducing the treatment fluid into a reaction zone in a subterranean formation, wherein the reaction zone has a temperature of at least 110° F. and a target reducing agent is present in the subterranean formation or in the well fluid. 
     
     
         59 . The method of  claim 58 , wherein the treatment fluid is introduced so as to achieve a ratio of approximately 2.5 to 5:1 by weight of chlorine dioxide precursor composition to the target reducing agent. 
     
     
         60 . The method of  claim 59 , the target reducing agent being hydrogen sulfide, iron sulfide or a combination thereof. 
     
     
         61 . The method of  claim 49 , wherein the well fluid comprises up to 20 mg/L chlorine dioxide. 
     
     
         62 . The method of  claim 49 , wherein the well fluid is a fracturing fluid. 
     
     
         63 . The method of  claim 54 , further comprising introducing the treatment fluid into a reaction zone in a subterranean formation, wherein the reaction zone has a temperature of at least 110° F. and a target reducing agent is present in the subterranean formation or in the well fluid. 
     
     
         64 . The method of  claim 63 , wherein the treatment fluid is applied so as to achieve a ratio of approximately 2.5 to 5:1 by weight of chlorine dioxide precursor composition to the target reducing agent. 
     
     
         65 . The method of  claim 64 , the target reducing agent being hydrogen sulfide, iron sulfide or a combination thereof.