Self-suspending proppants for hydraulic fracturing

Abstract

The invention provides for modified proppants, comprising a proppant particle and a hydrogel coating, wherein the hydrogel coating localizes on the surface of the proppant particle to produce the modified proppant, methods of manufacturing such proppants and methods of use.

1 . A modified proppant, comprising a proppant particle and a hydrogel coating, wherein the hydrogel coating localizes on the surface of the proppant particle to produce the modified proppant. 
     
     
         2 . (canceled) 
     
     
         3 . The modified proppant of  claim 1 , wherein the proppant particle comprises bauxite, sintered bauxite, ceramic, or low density proppant. 
     
     
         4 . The modified proppant of  claim 1 , wherein the proppant particle comprises a resin-coated substrate. 
     
     
         5 . (canceled) 
     
     
         6 . The modified proppant of  claim 1 , wherein the hydrogel coating comprises a water-swellable polymer. 
     
     
         7 . The modified proppant of  claim 6 , wherein the weight average molecular weight of the polymer is ≧ about 1 million g/mol, preferably ≧ about 5 million g/mol. 
     
     
         8 . The modified proppant of  claim 1 , wherein the proppant is free-flowing when dry or after being subjected to a relative humidity of between about 80%-90% for one hour at 25-35° C. 
     
     
         9 . The modified proppant of  claim 1 , wherein the proppant is dry. 
     
     
         10 . The modified proppant of  claim 1 , wherein the hydrogel coating is durable. 
     
     
         11 . The modified proppant of  claim 10 , wherein the shearing ratio of the proppant as determined by a Shear Analytical Test is ≧0.6. 
     
     
         12 . The modified proppant of  claim 1 , wherein the hydrogel coating is applied to the proppant particle as a liquid coating formulation that dries to form a substantially continuous film on the surface of the proppant particle. 
     
     
         13 . The modified proppant of  claim 1 , wherein the modified proppant is made by an invert emulsion coating technique in which the proppant particle substrate is combined with an invert emulsion in which the oil phase forms the continuous phase of the emulsion and a solution or dispersion of the superabsorbent polymer in water forms the discontinuous, emulsified phase. 
     
     
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         27 . The modified proppant of  claim 1 , further comprising an alcohol selected from the group consisting of ethylene glycol, propylene glycol, glycerol, propanol, and ethanol. 
     
     
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         42 . In a process for fracturing a geological formation penetrated by a well in which a fracing fluid containing a proppant is charged into the geological formation with pulsed pressure, a method for reducing the amount of thickening agent that is added to the fracing fluid comprising selecting as the proppant the modified proppant of  claim 1 . 
     
     
         43 . The method of  claim 42 , wherein the modified proppant hydrates essentially completely within 2 hours of first being combined with the fracing fluid. 
     
     
         44 . The method of  claim 43 , wherein the modified proppant hydrates essentially completely within 10 minutes of first being combined with the fracing fluid. 
     
     
         45 . A method of manufacturing a modified proppant, comprising:
 providing a proppant substrate particle and a fluid polymeric coating composition; and   applying the fluid polymeric coating composition on the proppant substrate particle;   wherein the fluid polymeric coating composition comprises a hydrogel polymer, and wherein the hydrogel polymer localizes on the surface of the proppant substrate particle to produce the modified proppant.   
     
     
         46 . The method of  claim 45 , further comprising the step of drying the modified proppant. 
     
     
         47 . The method of  claim 45 , wherein the step of drying dries the fluid polymeric coating so as to form a substantially continuous film on the surface of the modified proppant. 
     
     
         48 . (canceled) 
     
     
         49 . The method of  claim 45 , wherein the proppant substrate particle comprises sand, ceramic, low density proppant, a resin coated substrate, and/or bauxite. 
     
     
         50 . (canceled) 
     
     
         51 . The method of  claim 45 , further comprising adding an alcohol selected from the group consisting of ethylene glycol, propylene glycol, glycerol, propanol, and ethanol during or before the step of mixing the proppant substrate particles and the fluid polymer coating composition. 
     
     
         52 . (canceled) 
     
     
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         55 . A method of manufacturing a hydrogel-coated proppant, comprising:
 providing a proppant substrate particle and a formulation comprising a coating precursor, wherein the coating precursor is capable of forming a hydrogel coating on a surface of the proppant substrate particle by in situ polymerization;   applying the formulation to the proppant substrate particle; and   polymerizing the coating precursor in juxtaposition to the proppant substrate particle to form the hydrogel-coated proppant.   
     
     
         56 . (canceled)