US2005065041A1PendingUtilityA1

Gelled acid

39
Assignee: SCHLUMBERGER TECHNOLOGY CORPPriority: Sep 18, 2003Filed: Sep 18, 2003Published: Mar 24, 2005
Est. expirySep 18, 2023(expired)· nominal 20-yr term from priority
Inventors:Donald G. Hill
C09K 8/74
39
PatentIndex Score
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Cited by
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Claims

Abstract

Reducing agents or reducing agent precursors are provided for breaking ferric ion crosslinks in polymers in gelled acids used for diversion in matrix acidizing and used for leakoff control in acid fracturing. Previous reducing agents were very toxic to aquatic species or so active that they could be used only at low temperatures. The new reducing agents and reducing agent precursors are less reactive, less toxic, and leave less residue behind to impede fluid flow after the gel is broken after the treatment. Suitable compounds are sources of one or two hydrazines or sources of hydroxylamine. Such compounds are carbohydrazides, semicarbohydrazides, ketoximes, and aldoximes.

Claims

exact text as granted — not AI-modified
1 . An aqueous acid composition comprising 
 (a) an aqueous acid;    (b) a polymeric gelling agent that crosslinks in the presence of ferric ions at a pH of about 2 or greater;    (c) a soluble ferric salt in an amount sufficient to crosslink said polymeric gelling agent at a pH of about 2 or greater, but which does not crosslink said polymeric gelling agent at a pH below about 2; and    (d) an effective amount of a source of a reducing agent selected from the group consisting of hydroxylamine and a hydrazine.    
     
     
         2 . The composition of  claim 1  wherein the source of the hydrazine is selected from the group consisting of carbohydrazides having the formula  
         R 1 R 2 NN(R 3 )—C(O)NR 4 NR 5 R 6 ,  and semicarbohydrazides having the formula      R 1 R 2 NN(R 3 )—C(O)NR 4 R 5      wherein R 1  through R 6  may be the same or different and may be hydrogen or a branched, cyclic, or straight chained, saturated or unsaturated hydrocarbon having from 1 to about 6 carbon atoms.    
     
     
         3 . The composition of  claim 2  wherein the carbohydrazide is carbohydrazide wherein R 1  through R 6  are each hydrogen.  
     
     
         4 . The composition of  claim 2  wherein the semicarbohydrazide is semicarbohydrazide wherein R 1  through R 5  are each hydrogen.  
     
     
         5 . The composition of  claim 1  wherein the source of the hydroxylamine is selected from the group consisting of a aldoximes having the formula  
         R 7 HC═NOH,  and ketoximes having the formula      R 7 R 8 C═NOH    wherein R 7  and R 8  may be the same or different and may be a branched, cyclic, or straight chained, saturated or unsaturated hydrocarbon having from 1 to about 8 carbon atoms and further wherein R 7  and R 8  may form a ring.    
     
     
         6 . The composition of  claim 5  wherein the source of the hydroxylamine is selected from the group consisting of 2-butanone oxime, methyl isobutyl ketoxime, cyclohexanone oxime, acetaldoxime, butyraldoxime, propionaldoxime, heptaldoxime, 3-heptanone oxime, and acetophenone oxime.  
     
     
         7 . The composition of  claim 6  wherein the source of the hydroxylamine is 2-butanone oxime.  
     
     
         8 . A method of acidizing a subterranean formation penetrated by a wellbore comprising the step of injecting into said formation through said wellbore a fluid comprising 
 (a) an aqueous acid;    (b) a polymeric gelling agent that crosslinks in the presence of ferric ions at a pH of about 2 or greater;    (c) a soluble ferric salt in an amount sufficient to crosslink said polymeric gelling agent at a pH of about 2 or greater, but which does not crosslink said polymeric gelling agent at a pH below about 2; and    (d) an effective amount of a source of a reducing agent selected from the group consisting of hydroxylamine and a hydrazine.    
     
     
         9 . The method of  claim 8  wherein the source of the hydrazine is selected from the group consisting of carbohydrazides having the formula  
         R 1 R 2 NN(R 3 )—C(O)NR 4 NR 5 R 6 ,  and semicarbohydrazides having the formula      R 1 R 2 NN(R 3 )—C(O)NR 4 R 5      wherein R 1  through R 6  may be the same or different and may be hydrogen or a branched, cyclic, or straight chained, saturated or unsaturated hydrocarbon having from 1 to about 6 carbon atoms.    
     
     
         10 . The method of  claim 9  wherein the carbohydrazide is carbohydrazide wherein R 1  through R 6  are each hydrogen.  
     
     
         11 . The method of  claim 9  wherein the semicarbohydrazide is semicarbohydrazide wherein R 1  through R 5  are each hydrogen.  
     
     
         12 . The method of  claim 8  wherein the source of the hydroxylamine is selected from the group consisting of a aldoximes having the formula  
         R 7 HC═NOH,  and ketoximes having the formula      R 7 R 8 C═NOH    wherein R 7  and R 8  may be the same or different and may be a branched, cyclic, or straight chained, saturated or unsaturated hydrocarbon having from 1 to about 8 carbon atoms and further wherein R 7  and R 8  may form a ring.    
     
     
         13 . The method of  claim 12  wherein the source of the hydroxylamine is selected from the group consisting of 2-butanone oxime, methyl isobutyl ketoxime, cyclohexanone oxime, acetaldoxime, butyraldoxime, propionaldoxime, heptaldoxime, 3-heptanone oxime, and acetophenone oxime.  
     
     
         14 . The method of  claim 13  wherein the source of the hydroxylamine is 2-butanone oxime.  
     
     
         15 . The method of  claim 8  wherein the step of injecting into said formation through said wellbore is conducted at a pressure and flow rate sufficient to create a fracture in said formation.  
     
     
         16 . The method of  claim 15  wherein the source of the hydrazine is selected from the group consisting of carbohydrazides having the formula  
         R 1 R 2 NN(R 3 )—C(O)NR 4 NR 5 R 6 ,  and semicarbohydrazides having the formula      R 1 R 2 NN(R 3 )—C(O)NR 4 R 5      wherein R 1  through R 6  may be the same or different and may be hydrogen or a branched, cyclic, or straight chained, saturated or unsaturated hydrocarbon having from 1 to about 6 carbon atoms.    
     
     
         17 . The method of  claim 16  wherein the carbohydrazide is carbohydrazide wherein R 1  through R 6  are each hydrogen.  
     
     
         18 . The method of  claim 16  wherein the semicarbohydrazide is semicarbohydrazide wherein R 1  through R 5  are each hydrogen.  
     
     
         19 . The method of  claim 15  wherein the source of the hydroxylamine is selected from the group consisting of a aldoximes having the formula  
         R 7 HC═NOH,  and ketoximes having the formula      R 7 R 8 C═NOH    wherein R 7  and R 8  may be the same or different and may be a branched, cyclic, or straight chained, saturated or unsaturated hydrocarbon having from 1 to about 8 carbon atoms and further wherein R 7  and R 8  may form a ring.    
     
     
         20 . The method of  claim 19  wherein the source of the hydroxylamine is selected from the group consisting of 2-butanone oxime, methyl isobutyl ketoxime, cyclohexanone oxime, acetaldoxime, butyraldoxime, propionaldoxime, heptaldoxime, 3-heptanone oxime, and acetophenone oxime.  
     
     
         21 . The method of  claim 20  wherein the source of the hydroxylamine is 2-butanone oxime.

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