Polyols for breaking of fracturing fluid

Abstract

It has been discovered that fracturing fluid breaker mechanisms are improved by the inclusion of a polyol alone that directly degrades the polysaccharide backbone, and optionally additionally by removing the crosslinking ion, if present. That is, viscosity reduction (breaking) occurs by breaking down the chemical bonds within the backbone directly, rather than by merely removing the crosslinking ion, if presert. The gel does not have to be crosslinked for the method of the invention to be successful, although it may be crosslinked. In one non-limiting embodiment, the polyol has at least two hydroxyl groups on adjacent carbon atoms. In another embodiment, the polyols are monosaccharides such as glycerols and sugar alcohols, and may include mannitol, sorbitol, glucose, fructose, galactose, mannose, lactose, maltose, allose, etc. and mixtures thereof.

1 - 46 . (canceled)  
   
   
       47 . An aqueous fluid comprising: 
 at least one polysaccharide gel;    at least one polyol, in an amount effective to eventually reduce the pH of 
 the fluid and break down the polysaccharide backbone directly, where the polyol is selected from the group consisting of glycerol, glucose, lactose, rhamnose, mannose, alkyl glucoside and mixtures thereof; and  
   water; in the absence of an oxidizer breaker or an enzyme breaker.    
   
   
       48 . The fluid of  claim 47  where the polyol has at least one hydroxyl group on two adjacent carbon atoms and is selected from the group consisting of monosaccharides and disaccharides, and acid, acid salt, alcohol, alkyl and amine derivatives of these saccharides.  
   
   
       49 . The fluid of  claim 47  further comprising a compound selected from the group consisting of an alkali metal hydroxide, an alkali metal carbonate, bicarbonate, sesquicarbonate, and mixtures thereof to raise the pH to at least 8.0.  
   
   
       50 . (canceled)  
   
   
       51 . The fluid of  claim 47  where the polyol is selected from the group consisting of glucose, lactose, or alkyl glucoside.  
   
   
       52 . The fluid of  claim 47  where the amount of polyol ranges from about 0.01 to about 20 pptg (about 0.0012 to about 2.4 kg/m 3 ) based on the total volume of fluid.  
   
   
       53 . The fluid of  claim 47  where the polysaccharide is crosslinked.  
   
   
       54 . The fluid of  claim 52  where the polysaccharide is crosslinked with an ion selected from the group consisting of borate ion, zirconate ion, titanate ion, and combinations thereof.  
   
   
       55 . (canceled)  
   
   
       56 . An aqueous fluid comprising: 
 at least one polymer crosslinked with an ion of borate, zirconate, titanate, and combinations thereof;    at least one polyol, in an amount effective to eventually reduce the pH of the fluid, break down the polysaccharide backbone directly, and remove at least a portion of ion from the crosslinked polymer, where the polyol is selected from the group consisting of glycerol, glucose, lactose, rhamnose, mannose, alkyl glucoside and mixtures thereof;    at least one enzyme; and    water;    where the effective amount of polyol ranges from about 0.01 to 10.0 pptg (about 0.012 to 1.2 kg/m 3 ) based on the total volume of fluid.    
   
   
       57 . The fluid of  claim 56  where the polyol has at least one hydroxyl group on two adjacent carbon atoms.  
   
   
       58 . The fluid of  claim 56  where the polyol is selected from the group consisting of monosaccharides and disaccharides, and acid, acid salt, alcohol, alkyl and amine derivatives of these saccharides.  
   
   
       59 . (canceled)  
   
   
       60 . The fluid of  claim 56  where the enzyme is selected from the group consisting of hemi-cellulases, cellulases, pectinases, and alpha-amylases.  
   
   
       61 . The fluid of  claim 56  where the amount of enzyme ranges from about 0.001 to about 5.0 gptg based on the total volume of fluid.  
   
   
       62 . The fluid of  claim 61  where the crosslinked polymer is a guar or guar-based polymer and the enzyme is effective to break linkages selected from the group consisting of 1,4-β-D-mannosidic linkages; 1,6-α-D-glactomannosidic linkages; and mixtures thereof at a pH in the range of from about 2 to about 11.  
   
   
       63 . An aqueous fluid comprising: 
 at least one polysaccharide gel;    at least one polyol in an ranging from about 0.01 to about 20 pptg (about 0.0012 to about 2.4 kg/m 3 ) based on the total volume of fluid, where the polyol is selected from the group consisting of glycerol, glucose, lactose, rhamnose, mannose, alkyl glucoside and mixtures thereof;    water; and    a compound selected from the group consisting of an alkali metal hydroxide, an alkali metal carbonate, bicarbonate, sesquicarbonate, and mixtures thereof to raise the pH to at least 8.0; in the absence of an oxidizer breaker or an enzyme breaker.    
   
   
       64 . The fluid of  claim 63  where the polyol is selected from the group consisting of glucose, lactose, or alkyl glucoside.  
   
   
       65 . The fluid of  claim 63  where the polysaccharide is crosslinked.  
   
   
       66 . The fluid of  claim 65  where the polysaccharide is crosslinked with an ion selected from the group consisting of borate ion, zirconate ion, titanate ion, and combinations thereof.