Deep eutectic solvents and applications

Abstract

A method of solubilizing/removing cellulose or chemically-modified cellulosic polymers utilized in subterranean drilling operations such as fracturing. The method involves introducing a deep eutectic solvent (DES) into a subterranean region. Deep eutectic solvents useful as cellulose solvents include quaternary ammonium compounds, including choline chloride and chlorcholine chloride, reacted with a compound selected from amides, amines, carboxylic acids alcohols, and metal halides. The DES material can be pumped downhole after fracturing operations to remove cellulosic material used, for example, to thicken fracturing fluid which is left behind in the created fractures, on the face of the formation, along the wellbore, or elsewhere within the subterranean region. The DES can be used alone or in a sequential treatment protocol, whereby the DES is introduced into the subterranean region, followed by post-treatment introduction of water, caustic, acid or anhydride into the subterranean as a flush.

1 . A method of treating a subterranean region, the method comprising:
 providing a eutectic solvent; and   introducing the eutectic solvent into the subterranean region,   
       wherein providing a eutectic solvent comprises reacting an ammonium compound with a second compound selected from the group consisting of amines, amides, carboxylic acids, alcohols, metal halides, and combinations thereof. 
     
     
         2 . The method of  claim 1  wherein the ammonium compound is a quaternary ammonium compound. 
     
     
         3 . The method of  claim 2  wherein the quaternary ammonium compound is selected from quaternary ammonium halides. 
     
     
         4 . The method of  claim 3  wherein the quaternary ammonium compound is selected from quaternary ammonium chlorides. 
     
     
         5 . The method of  claim 2 , wherein the ammonium compound is selected from the group consisting of compounds having the structures:
   R 1 R 2 R 3 —N R 4 Cl and ClR 1 R 2 R 3 —N R 4 Cl,
   
       wherein R 1 , R 2 , and R 3  are selected from the group consisting of hydrogen and linear or branched alkyl, aryl, or alkylaryl groups C x H y , where 1≦x≦18 and 3≦y≦37, and R 4  is selected from the group consisting of hydrogen and groups having the structure C x H y  or C x H y OH, where 1≦x≦18 and 3≦y≦37. 
     
     
         6 . The method of  claim 5  wherein R 1 , R 2 , R 3 , and R 4  are each selected from the group consisting of hydrogen, methyl-, ethyl-, octadecyl-, phenyl, benzyl- methoxy-, and ethoxy-groups. 
     
     
         7 . The method of  claim 5 , wherein the ammonium compound is ammonium chloride. 
     
     
         8 . The method of  claim 5  wherein the ammonium compound is a quaternary ammonium chloride, wherein none of R 1 , R 2 , R 3 , and R 4  is hydrogen. 
     
     
         9 . The method of  claim 8  wherein the ammonium compound is selected from the group consisting of chlorcholine chloride and choline chloride. 
     
     
         10 . The method of  claim 1  wherein the second compound has a chain length (C length ) of 1≦C length ≦18. 
     
     
         11 . The method of  claim 1  wherein the second compound is urea, H 2 N—CO—NH 2 . 
     
     
         12 . The method of  claim 1  wherein the second compound is a di-functional amine selected from the group consisting of compounds with the structure:
   R 1 —(CH 2 ) x —R 2 ,
 
 
       wherein 2≦x≦6, and R 1  and R 2  are selected from the group consisting of —NH 2 , —NHR 3 , and —NR 3 R 4 , where R 3  and R 4  are selected from alkyl, aryl, and alkylaryl groups. 
     
     
         13 . The method of  claim 12  wherein the di-functional amine is ethylene diamine, H 2 N—(CH 2 ) 2 —NH 2 . 
     
     
         14 . A method of treating a subterranean region, the method comprising:
 providing an ammonium halide;   reacting the ammonium halide with a hydrogen bond donor to provide a deep eutectic solvent; and   introducing the deep eutectic solvent into a subterranean region.   
     
     
         15 . The method of  claim 14  wherein the subterranean region was previously treated with a drilling fluid or a fracturing fluid comprising cellulosic material. 
     
     
         16 . The method of  claim 14  wherein the deep eutectic solvent is capable of solubilizing up to 30 wt % cellulosic material. 
     
     
         17 . The method of  claim 14  wherein the deep eutectic solvent is introduced into the subterranean region as an additive in a fracturing or other drilling fluid. 
     
     
         18 . The method of  claim 14  wherein the ammonium halide is selected from the group consisting of quaternary ammonium chlorides. 
     
     
         19 . The method of  claim 14  wherein the ammonium halide is selected from the group consisting of chlorcholine chloride, choline chloride, ammonium chloride, and combinations thereof. 
     
     
         20 . The method of  claim 14  wherein the hydrogen bond donor is selected from amides, carboxylic acids, alcohols and metal halides. 
     
     
         21 . The method of  claim 20  wherein the hydrogen bond donor is selected from amides. 
     
     
         22 . The method of  claim 21  wherein the hydrogen bond donor is selected from the group consisting of urea, 1-methyl urea, dimethyl urea, thiourea, acetamide, and combinations thereof. 
     
     
         23 . The method of  claim 22  wherein the hydrogen bond donor is urea. 
     
     
         24 . The method of  claim 14  further comprising introducing one or more wash solution into the subterranean following introducing the deep eutectic solvent into a subterranean region. 
     
     
         25 . The method of  claim 24  wherein the one or more wash solution is selected from the group consisting of caustic solutions, acid solutions, anhydride solutions, water, and combinations thereof. 
     
     
         26 . The method of  claim 25  wherein more than one wash solution is introduced into the subterranean region in series. 
     
     
         27 . A method of treating a subterranean region for removal of cellulosic material therein or prevention of deposition of cellulosic material therein, the method comprising:
 reacting a quaternary ammonium chloride selected from the group consisting of chlorcholine chloride and choline chloride with a hydrogen bond donor selected from the group consisting of amides, carboxylic acids, alcohols and metal halides to produce a deep eutectic solvent; and   introducing the deep eutectic solvent into the subterranean region, whereby cellulosic material is solubilized in the deep eutectic solvent.   
     
     
         28 . The method of  claim 27  wherein the deep eutectic solvent is introduced into the subterranean region as an additive to a fracturing fluid comprising cellulosic material. 
     
     
         29 . The method of  claim 27  wherein the subterranean region was treated with a fracturing fluid or drilling fluid comprising cellulosic material prior to introducing the deep eutectic solvent therein. 
     
     
         30 . The method of  claim 27  wherein the quaternary ammonium chloride is chlorcholine chloride and the hydrogen bond donor is urea. 
     
     
         31 . The method of  claim 27  wherein the quaternary ammonium chloride is choline chloride and the hydrogen bond donor is urea. 
     
     
         32 . The method of  claim 27  wherein reacting comprises combining the quaternary ammonium chloride and the hydrogen bond donor to form a mixture, and heating the mixture to a temperature of greater than 70° C.