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 . A chlorine dioxide precursor composition comprising an aqueous solution of 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 110° F. or greater. 
     
     
         48 . The composition of  claim 47 , wherein the chlorate salt comprises sodium chlorate and the weak acid comprises citric acid. 
     
     
         49 . The composition of  claim 48 , wherein the composition does not comprise a strong acid. 
     
     
         50 . The composition of  claim 48 , wherein the composition further comprises a strong acid at a concentration of about 0.1% to 2% by weight. 
     
     
         51 . The composition of  claim 50 , wherein the strong acid is hydrochloric acid, hydrofluoric acid, or a mixture thereof. 
     
     
         52 . The composition of  claim 47 , wherein the reducing agent is iron sulfide. 
     
     
         53 . A well fluid to which the precursor composition of  claim 47  is added at a concentration from about 100 to 10,000 mg/l. 
     
     
         54 . A chlorine dioxide precursor composition comprising an aqueous solution of sodium chlorate at 5% to 40% by weight and citric acid at 5% to 20% by weight, wherein the composition is stable at a temperature below about 90° F. and wherein the composition reacts to form chlorine dioxide when exposed to iron sulfide in combination with a temperature of about 115° F. or greater. 
     
     
         55 . A well fluid to which the precursor composition of  claim 54  is added at a concentration from about 100 to 10,000 mg/l. 
     
     
         56 . A method of treating an aqueous fluid for introduction into a reaction zone having a temperature of at least about 110° F. and comprising one or more reducing agents, the method comprising adding to the aqueous fluid a chlorine dioxide precursor composition comprising an aqueous solution of a chlorate salt at a concentration of 5 to 40% by weight and an acid at a concentration of 5 to 20% by weight, 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. 
     
     
         57 . The method of  claim 56 , wherein the chlorate salt comprises sodium chlorate and the weak acid comprises citric acid. 
     
     
         58 . The method of  claim 56 , wherein the composition does not comprise a strong acid. 
     
     
         59 . The method of  claim 56 , wherein the composition further comprises a strong acid at a concentration of about 0.1% to 2% by weight. 
     
     
         60 . The method of  claim 59 , wherein the strong acid is hydrochloric acid, hydrofluoric acid, or a mixture thereof. 
     
     
         61 . The method of  claim 56 , wherein the chlorine dioxide precursor composition is added to the aqueous fluid at a concentration from about 100 to 10,000 mg/l. 
     
     
         62 . The method of  claim 56 , further comprising introducing the aqueous fluid into a subterranean formation such that it enters a reaction zone within the subterranean formation that has a temperature of at least about 110° F. and comprises a target reducing agent. 
     
     
         63 . The method of  claim 62 , wherein said target reducing agent comprises one or more of elemental sulfur, a reduced sulfur compound, a reduced organic compound, and a reduced metal ion. 
     
     
         64 . The method of  claim 62 , wherein the chlorine dioxide precursor composition is added to the aqueous fluid at a ratio of approximately 2.5 to 5:1 by weight of chlorine dioxide precursor composition to target reducing agent, and wherein said target reducing agent comprises one or more reduced sulfur compounds or reduced metal ions.