Acidizing stimulation method using viscoelastic gelling agent

Abstract

A method of acidizing a subterranean formation involves the use of a composition containing a solution of a viscoelastic amidoamine oxide surfactant and an HF-containing acidizing solution. The composition typically contains from about 0.1 to about 8 weight percent of surfactant solution and from about 92 to about 99.9 weight percent of HF-containing acidizing solution. The composition is pumped into the subterranean formation. As the acid reacts, the composition viscosifies and becomes a self-diverting agent created in-situ. When the acid is further spent, the fluid viscosity declines eventually returning to a low viscosity state, allowing for easy cleanup. The process allows for selective acidizing of less permeable zones of the formation and more uniform stimulation of the hydrocarbon bearing formulation.

1 . A process for enhancing the productivity of a hydrocarbon well which comprises introducing into the well a composition comprising: 
 (a) an HF-containing acidizing solution; and    (b) a solution of an amidoamine oxide gelling agent.    
     
     
         2 . The process of  claim 1 , wherein the solution of amidoamine oxide gelling agent further comprises at least one glycol.  
     
     
         3 . The process of  claim 2 , wherein the weight percent of the glycol solution in the composition is between from about 0.1 to about 8 weight percent.  
     
     
         4 . The process of  claim 1 , wherein the gelling agent comprises at least one amidoamine oxide of the formula:  
       
         
           
           
               
               
           
         
       
       wherein R 1  is a saturated or unsaturated, straight or branched chain aliphatic group of from about 7 to about 30 carbon atoms, R 2  is a straight chain or branched, substituted or unsubstituted divalent alkylene group of from 2 to about 6 carbon atoms, R 3  and R 4  are independently selected from alkyl or hydroxyalkyl groups of from 1 to about 4 carbon atoms or R 3  and R 4  together with the nitrogen atom to which these groups are bonded form a heterocyclic ring of up to 6 members; and R 5  is hydrogen or a C 1 -C 4  alkyl or hydroxyalkyl group.  
     
     
         5 . The process of  claim 2 , wherein the amount of amidoamine oxide gelling agent in the glycol solution is between from about 40 to about 65 weight percent.  
     
     
         6 . The process of  claim 5 , wherein the preferred amount of amidoamine oxide gelling agent in the glycol solution is about 50 weight percent.  
     
     
         7 . The process of  claim 1 , wherein the acidizing solution further comprises a phosphonate of the formula:  
       
         
           
           
               
               
           
         
       
       wherein R1, R2 and R3 are independently selected from hydrogen, alkyl, aryl, phosphonates, phosphates, acyl, amine, hydroxyl and carboxyl groups and R4 and R5 are independently selected from hydrogen, sodium, potassium, ammonium or an organic radical.  
     
     
         8 . The process of  claim 7 , wherein the acidizing solution further comprises citric acid, formic acid or acetic acid.  
     
     
         9 . The process of  claim 8 , wherein the acidizing solution comprises about 1 to about 50 weight percent citric acid, up to about 20 weight percent HF and from about 0.5 to about 50 weight percent phosphonate compound.  
     
     
         10 . The process of  claim 1 , wherein the amidoamine oxide gelling agent is selected from the group consisting of tallow amidoalkylamine oxide, hydrogenated tallow amidoalkyl dialkylamine oxide, rapeseed amidoalkylamine oxide, hydrogenated rapeseed amidoalkylamine oxide, tall oil amidoalkylamine oxide, hydrogenated tall oil amidoalkylamine oxide, coco amidoalkylamine oxide, stearyl amidoalkylamine oxide, oleyl amidoalkylamine oxide, soya amidoalkylamine oxide, erucyl amidoalkylamine oxide, C 14 -C 22  saturated or unsaturated fatty acid amidoalkyl amine oxides, and mixtures thereof.  
     
     
         11 . The process of  claim 2 , wherein the at least one glycol is selected from ethylene glycol, butylene glycol, diethylene glycol, polypropylene glycol, polyethylene glycol, glycerin, propylene glycol, tetramethylene glycol, tetramethylethylene glycol and trimethylene glycol.  
     
     
         12 . A process for acidizing a formation penetrated by a well, comprising: 
 (a). forming a mixture of an HF-containing acidizing solution and a glycol solution of an amidoamine oxide gelling agent;    (b). pumping the mixture of step (a). into a portion of the formation.    
     
     
         13 . The process of  claim 12 , wherein the amidoamine oxide gelling agent is tallow amidopropyldimethylamine oxide.  
     
     
         14 . A method for selectively acidizing the less permeable zones of a subterranean formation penetrated by a well having a plurality of zones with varying permeabilities communicating with the well, which comprises: 
 (a). introducing into the formation a low viscosity fluid mixture of an HF-containing acidizing solution and a glycol solution of an amidoamine oxide gelling agent;    (b). generating in situ a self-diverting acid fluid by increasing the viscosity of the low viscosity fluid mixture; and    (c). selectively reducing flow to the more permeable zones of the formation with the self-diverting acid fluid, thereby diverting additional fluid into less permeable zones of the formation.    
     
     
         15 . The method of  claim 14 , wherein the gelling agent comprises at least one amidoamine oxide of the formula:  
       
         
           
           
               
               
           
         
       
       wherein R 1  is a saturated or unsaturated, straight or branched chain aliphatic group of from about 7 to about 30 carbon atoms, R 2  is a straight chain or branched, substituted or unsubstituted divalent alkylene group of from 2 to about 6 carbon atoms, R 3  and R 4  are independently selected from alkyl or hydroxyalkyl groups of from 1 to about 4 carbon atoms or R 3  and R 4  together with the nitrogen atom to which these groups are bonded form a heterocyclic ring of up to 6 members; and R 5  is hydrogen or a C 1 -C 4  alkyl or hydroxyalkyl group.  
     
     
         16 . The process of  claim 14 , wherein the amount of amidoamine oxide gelling agent in the glycol solution is between from about 40 to about 65 weight percent.  
     
     
         17 . The process of  claim 14 , wherein the acidizing solution further comprises a phosphonate of the formula:  
       
         
           
           
               
               
           
         
       
       wherein R1, R2 and R3 are independently selected from hydrogen, alkyl, aryl, phosphonates, phosphates, acyl, amine, hydroxyl and carboxyl groups and R4 and R5 are independently selected from hydrogen, sodium, potassium, ammonium or an organic radical.  
     
     
         18 . The process of  claim 17 , wherein the acidizing solution further comprises citric acid, formic acid or acetic acid.  
     
     
         19 . The process of  claim 14 , wherein the amidoamine oxide gelling agent is selected from the group consisting of tallow amidoalkylamine oxide, hydrogenated tallow amidoalkyl dialkylamine oxide, rapeseed amidoalkylamine oxide, hydrogenated rapeseed amidoalkylamine oxide, tall oil amidoalkylamine oxide, hydrogenated tall oil amidoalkylamine oxide, coco amidoalkylamine oxide, stearyl amidoalkylamine oxide, oleyl amidoalkylamine oxide, soya amidoalkylamine oxide, erucyl amidoalkylamine oxide, C 14 -C 22  saturated or unsaturated fatty acid amidoalkyl amine oxides, and mixtures thereof.  
     
     
         20 . The process of  claim 14 , wherein the at least one glycol is selected from ethylene glycol, butylene glycol, diethylene glycol, polypropylene glycol, polyethylene glycol, glycerin, propylene glycol, tetramethylene glycol, tetramethylethylene glycol and trimethylene glycol.