Method for enhancing acidizing treatment of a formation having a high bottom hole temperature

Abstract

An injection process to treat sandstone or limestone subterranean formations using carboxylic acids, dicarboxylic acids and/or aminocarboxylic acids (e.g. glutamic acid N,N-diacetic acid (GLDA); methylglycine N,N-diacetic acid (MGDA); diethylene triamine pentaacetic acid (DTPA), etc.), further involves at least a two step injection process which may include, in one non-limiting embodiment, injecting a relatively higher concentration of organic acid to create wormholes accompanied by a relatively lower concentration of the same or different organic acid to enhance the permeability of the formation.

What is claimed is: 
     
         1 . A method for acidizing a subterranean formation, the method comprising:
 injecting through a wellbore in the subterranean formation a first acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a first step, where the first acid has a first concentration and a first volume; and   injecting through the wellbore a second acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a second step, where the second acid has a second concentration and a second volume;   
       where:
 the first step differs from the second step by a parameter selected from the group consisting of:
 the first concentration is greater than the second concentration; 
 the first concentration is greater than the second concentration and the first volume is less than the second volume; 
 the first volume is greater than the second volume, where the first concentration is less than the second concentration; 
 the second acid is at least partially neutralized by the addition of a base; 
 the first acid is a carboxylic acid or its salt with a pH ranging from about 4 to about 12 and the second acid is a carboxylic acid with a pH ranging from about 1 to about 4; and 
 combinations thereof; and 
 
 the bottom hole temperature of the wellbore is at least 150° F. (65.5° C.). 
 
     
     
         2 . The method of  claim 1  where the first concentration ranges from about 10 to about 40 wt % acid, and the second concentration ranges from about 0.01 to about 10 wt % acid. 
     
     
         3 . The method of  claim 1  where the second volume of acid is greater than the first volume of acid by an amount ranging from about 5 times to about 200 times greater volume more. 
     
     
         4 . The method of  claim 1  where the first acid and the second acid are the same acid. 
     
     
         5 . The method of  claim 1  where:
 the first concentration ranges from about 11 to about 40 wt %; 
 the second acid is at least partially neutralized by the addition of a base selected from the group consisting of oxides of Groups 1, 2 and combinations thereof, hydroxides of Groups 1, 2 and combinations thereof, and combinations thereof; and 
 the bottom hole temperature is between about 150 and about 350° F. (about 65.5 and about 177° C.). 
 
     
     
         6 . The method of  claim 1  where:
 the first concentration ranges from about 5 to about 40 wt %; 
 the second concentration is less than 5 wt %; 
 the second acid is at least partially neutralized by the addition of a base selected from the group consisting of oxides of Groups 1, 2 and combinations thereof, hydroxides of Groups 1, 2 and combinations thereof, and combinations thereof; and 
 the bottom hole temperature is between greater than about 300° F. (about 149° C.). 
 
     
     
         7 . The method of  claim 1  further comprising injecting through the wellbore a third acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of dicarboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a third step, where the third acid has a third concentration ranging between about 0.01 to about 10 wt %. 
     
     
         8 . The method of  claim 1  where the carboxylic acids and aminocarboxylic acids are selected from the group consisting of glutamic acid N,N-diacetic acid (GLDA); methylglycine N,N-diacetic acid (MGDA); diethylene triamine pentaacetic acid (DTPA); nitrilotriacetic acid (NTA); ethylene diamine tetraacetic acid (EDTA); hydroxyethyl ethylene diamine triacetic acid (HEDTA); diethylene triamine pentaacetic acid (DTPA); propylene diamine tetraacetic acid (PDTA); ethylene diamine-N,N″-di(hydroxyphenyl acetic) acid (EDDHA); ethylene diamine-N,N″-di(hydroxy-methylphenyl acetic) acid (EDDHMA); ethanol diglycine (EDG); trans-1,2-cyclohexylene dinitrilotetraacetic acid (CDTA); glucoheptonic acid; gluconic acid; sodium citrate; acetic acid; formic acid; lactic acid; citric acid; malonic acid; succinic acid; adipic acid; glutaric acid; malic acid; tartaric acid; alkali metal salts of these acids; amine salts of these acids; and combinations thereof. 
     
     
         9 . The method of  claim 1  where the carboxylic acid is a dicarboxylic acid. 
     
     
         10 . The method of  claim 1  where the subterranean formation comprises formations selected from the group consisting of sandstone formations, limestone formations, and combinations thereof. 
     
     
         11 . The method of  claim 1  where the permeability of the subterranean formation is increased compared to a method that consists of only injecting the first acid or only injecting the second acid. 
     
     
         12 . A method for acidizing a subterranean formation, the method comprising:
 injecting through a wellbore in the subterranean formation a first acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a first step, where the first acid has a first concentration between 10 to about 40 wt % and a first volume;   followed by injecting through the wellbore a second acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a second step, where the second acid has a second concentration between about 0.01 and less than 10 wt % and a second volume; and   the bottom hole temperature of the wellbore is at least 150° F. (65.5° C.).   
     
     
         13 . A method for acidizing a subterranean formation, the method comprising:
 injecting through a wellbore in the subterranean formation a first acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a first step, where the first acid has a first concentration from about 10 to about 40 wt % acid, and a first volume; and   followed by injecting through the wellbore a second acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a second step, where the second acid has a second concentration from about 0.5 to about 38 wt % acid, and a second volume that is higher than the first volume of acid by an amount ranging from about 5 to about 200 times more; and   the bottom hole temperature of the wellbore is at least 150° F. (65.5° C.).   
     
     
         14 . A method for acidizing a subterranean formation, the method comprising:
 injecting through a wellbore in the subterranean formation a first acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a first step, where the first acid has a first concentration from about 10 to about 40 wt % acid, and a first volume; and   injecting through the wellbore a second acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a second step, where the second acid has a second concentration from about 0.01 to about 10 wt % acid, and a second volume;   
       where:
 the first acid and the second acid are the same acid; and 
 the bottom hole temperature of the wellbore is at least 150° F. (65.5° C.). 
 
     
     
         15 . A method for acidizing a subterranean formation, the method comprising:
 injecting through a wellbore in the subterranean formation a first acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a first step, where the first acid has a first concentration between about 11 to about 40 wt %, and a first volume; and   injecting through the wellbore a second acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a second step, where the second acid has a second concentration from about 5 to about 10 wt %, and a second volume, the second acid at least partially neutralized by the addition of a base;   
       where:
 the bottom hole temperature of the wellbore is between about 150 and about 350° F. (about 65.5 and about 177° C.). 
 
     
     
         16 . A method for acidizing a subterranean formation, the method comprising:
 injecting through a wellbore in the subterranean formation a first acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a first step, where the first acid has a first concentration between 5 to about 40 wt %, and a first volume; and   injecting through the wellbore a second acid selected from the group consisting of carboxylic acids, aminocarboxylic acids, alkali metal salts and amine salts of carboxylic acids, alkali metal salts and amine salts of aminocarboxylic acids, and combinations thereof in a second step, where the second acid has a second concentration of less than 5 wt %, and a second volume, the second acid at least partially neutralized by the addition of a base;   
       where:
 the bottom hole temperature of the wellbore is greater than 300° F. (about 149° C.). 
 
     
     
         17 . A method for acidizing a subterranean formation, the method comprising:
 injecting through a wellbore in the subterranean formation a first acid selected from the group consisting of carboxylic acids, alkali metal salts and amine salts of carboxylic acids, and combinations thereof in a first step, where the first acid has a first concentration and a first volume, the first acid having a pH adjusted by the presence of a base to be in the range of from about 4 to about 12; and   injecting through the wellbore a second acid selected from the group consisting of carboxylic acids, alkali metal salts and amine salts of carboxylic acids, and combinations thereof in a second step, where the second acid has a second concentration and a second volume and a pH in the range of from about 1 to about 4;   
       where:
 the bottom hole temperature of the wellbore is at least 150° F. (65.5° C.).