Produced Water Borate Crosslinking Compositions and Method of Use

Abstract

A composition and method for treating a fracturing fluid comprising produced water with high levels of dissolved solids using a polymer crosslinked with a boron compound and a high pH alkylamine buffer. The composition improves the viscosity stability of the fracturing fluid at elevated bottom-hole temperatures, particularly when the fluid has high levels of calcium and magnesium. The composition is particularly useful with polysaccharides, including galactomannan gums, such as guar gum, locust bean gum, and karaya gum, and allows for the use of the preferred boron compound crosslinkers in high total dissolved solids fracturing fluids without the pH destabilization problems encountered with the prior art.

We claim: 
     
         1 . A treatment composition for increasing the viscosity of a fracturing fluid, the composition comprising:
 a galactomannan polymer;   a boron compound capable of crosslinking with the polymer;   a pH buffer comprising an amine, the pH buffer capable of maintaining the pH of the composition in the fracturing fluid above 9.0 at temperatures greater than 80° F.;   wherein the concentration of pH buffer is between 0.25 to 30 gpt.   
     
     
         2 . The treatment composition of  claim 1  further comprising a secondary pH buffer having an alkaline pH. 
     
     
         3 . The treatment composition of  claim 1  wherein the amount of pH buffer comprising an amine is at least about 3 times the amount of boron compound, by weight. 
     
     
         4 . The treatment composition of  claim 3  wherein the amount of galactomannan polymer is at least about 3 times the amount of boron compound, by weight. 
     
     
         5 . The treatment composition of  claim 1  wherein the polymer is guar gum and the boron compound is selected from the group consisting of boric acid, borax, sodium borate, disodium tetraborate, sodium tetraborate, sodium tetraborate decahydrate, amino boric acid, elluite, ulexite, colemanite, probertite, and mixtures thereof. 
     
     
         6 . The treatment composition of  claim 5  wherein the pH buffer is selected from the group consisting of n-butylamine, diethylenetriamine, diaminobutane, diethyldiamine, diisopropylamine, dodecylamine, ethylamine, ethylenediamine, di-(gamma-aminopropylether), methyleneamine, piperazine, triethylenetetramine, tetraethylenepentamine, triethylamine, amino diols, glycols poly glycols, and mixtures thereof. 
     
     
         7 . The treatment composition of  claim 1  wherein the fracturing fluid comprises produced water. 
     
     
         8 . The treatment composition of  claim 7  wherein the fracturing fluid comprises greater than 1,500 ppm total dissolved solids. 
     
     
         9 . The treatment composition of  claim 7  wherein the fracturing fluid comprises greater than 10,000 ppm total dissolved solids. 
     
     
         10 . The treatment composition of  claim 7  wherein the fracturing fluid comprises greater than 100,000 ppm total dissolved solids. 
     
     
         11 . The treatment composition of  claim 7  wherein the fracturing fluid water comprises calcium levels greater than about 500 ppm or magnesium levels greater than about 150 ppm. 
     
     
         12 . The treatment composition of  claim 11  wherein the polymer is guar gum and the pH buffer is DETA. 
     
     
         13 . A fracturing fluid comprising:
 a liquid comprising greater than 1,500 ppm total dissolved solids;   a polymer soluble in the liquid;   a boron crosslinking agent capable of increasing the viscosity of the fracturing fluid by crosslinking with the polymer;   a pH buffer comprising an amine, the pH buffer capable of maintaining the pH of the fracturing fluid above 9.0 at temperatures greater than 80° F.   
     
     
         14 . The fracturing fluid of  claim 13  comprising about 5 to 100 ppt polymer, 0.25 to 20 gpt boron crosslinking agent, and 0.25 to 30 gpt pH buffer. 
     
     
         15 . The fracturing fluid of  claim 14  wherein the polymer is a galactomannan polymer and the pH buffer is an alkylamine, and wherein the amount of alkylamine used is at least 3 times the amount of boron crosslinking agent, by weight. 
     
     
         16 . The fracturing fluid of  claim 13  wherein the pH buffer is capable of maintaining the pH of the fracturing fluid above 9.0 at temperatures greater than 190° F. 
     
     
         17 . The fracturing fluid of  claim 16  comprising about 7.6 to about 8.7 ppt boric acid and about 3.2 to about 4.6 gpt amine pH buffer. 
     
     
         18 . A treatment composition for increasing the viscosity of a fracturing fluid, the composition comprising:
 a polysaccharide polymer;   a boron compound capable of crosslinking with the polymer;   an alkylamine pH buffer capable of maintaining the pH of the composition in the fracturing fluid above 9.0 at temperatures greater than 80° F.;   wherein the amount of alkylamine is at least about 3 times the amount of boron compound and the amount of polymer is at least about 3 times the amount of boron compound, by weight.   
     
     
         19 . The treatment composition of  claim 18  wherein the polymer is a slurry of guar gum and oil comprising about 3 to 5 pounds of guar per gallon of slurry. 
     
     
         20 . The treatment composition of  claim 19  wherein the alkylamine is DETA and the boron compound is boric acid. 
     
     
         21 . The treatment composition of  claim 20  wherein the fracturing fluid comprises produced water and has calcium levels greater than about 500 ppm or magnesium levels greater than about 150 ppm. 
     
     
         22 . The treatment composition of  claim 21  comprising about 4 to 6 gpt polymer slurry, about 4.3 to 7 ppt boric acid, and about 0.5 to 3.5 gpt alkylamine. 
     
     
         23 . The treatment composition of  claim 18  comprising about 30 to 40 ppt polysaccharide polymer, about 4.3 to 7 ppt boron compound, and about 3.2 to about 4.6 gpt alkylamine buffer; and
 wherein the polysaccharide polymer is guar gum and the boron compound is boric acid. 
 
     
     
         24 . A method of treating a fracturing fluid to maintain a stable crosslink viscosity, the method comprising:
 providing a fracturing fluid comprising produced waters and having a total dissolved solids level greater than 1,500 ppm;   adding a polysaccharide to the fracturing fluid to hydrate the polysaccharide;   adding an alkylamine pH buffer to the fracturing the fluid, the alkylamine pH buffer being capable of maintaining the fracturing fluid at a pH level greater than 9.0 at temperatures greater than about 80° F.;   adding a boron crosslinking compound to the fracturing fluid;   wherein the alkylamine pH buffer is not added until after the polysaccharide has had sufficient time to hydrate in the fracturing fluid.   
     
     
         25 . The method of  claim 24  wherein the polysaccharide is mixed with oil to form a slurry comprising about 3-5 pounds of polysaccharide per gallon of slurry prior to adding to the fracturing fluid. 
     
     
         26 . The method of  claim 25  wherein about 4 to 6 gpt polysaccharide slurry, about 0.4 to 0.6 gpt boron compound, and about 0.5 to 3.5 gpt alkylamine are added to the fracturing fluid. 
     
     
         27 . The method of  claim 25  wherein the boron crosslinking compound is mixed with a secondary pH buffer having an alkaline pH to form a crosslinker-buffer solution prior to adding to the fracturing fluid. 
     
     
         28 . The method of  claim 27  wherein about 4 to 6 gpt polysaccharide slurry, about 1.5 to 4 gpt crosslinker-buffer solution, and about 0.5 to 3.5 gpt alkylamine are added to the fracturing fluid.