Stabilized Fluids In Well Treatment

Abstract

Proppant pillar placement in a fracture with a stabilized slurry treatment fluid. A method of placing a proppant pack by injecting a well treatment fluid comprising proppant and a stabilized slurry, and a slurry destabilizing system to consolidate solids from the slurry, and placing the proppant in the fracture in a plurality of proppant clusters forming pillars spaced apart by fluid flow channels from the formation through the fracture toward the wellbore. Also, a system for implementing the method, and the propped fracture system obtained as a result of placing the proppant pack into the fracture according to the method.

What is claimed is: 
     
         1 . A method of placing a proppant pack into a fracture formed in a subterranean formation, the method comprising:
 injecting a well treatment fluid through a wellbore into a fracture in a subterranean formation, wherein at least a portion of the well treatment fluid comprises a proppant-containing stage, wherein at least a portion of the well treatment fluid comprises a stabilized slurry stage and wherein the proppant-containing and stabilized slurry portions may be the same or different;   injecting a destabilizing system into the fracture with the well treatment fluid to destabilize the slurry stage and form regions of consolidated proppant from the destabilized slurry stage; and   placing a plurality of proppant clusters forming pillars from the consolidated proppant regions spaced apart by fluid flow channels from the formation through the fracture toward the wellbore.   
     
     
         2 . The method of  claim 1  wherein the stabilized slurry comprises a liquid phase, and wherein the slurry destabilizing system comprises a liquid-removing agent to remove fluid from the slurry. 
     
     
         3 . The method of  claim 2  wherein the liquid phase comprises water and the liquid-removal agent comprises a hydratable compound. 
     
     
         4 . The method of  claim 2  wherein the liquid phase comprises water and the liquid-removal agent comprises a superabsorbent polymer. 
     
     
         5 . The method of  claim 1 , further comprising:
 sequentially injecting a first stage of the treatment fluid into the formation followed by a second stage of the treatment fluid, wherein the first and second stages have different viscosities, different specific gravities, or both, to initiate viscous fingering;   wherein the stabilized slurry comprises the proppant in the first stage;   wherein the destabilizing system comprises a crosslinkable material in the first stage, and a crosslinking agent in at least one of the first and second stages to crosslink the crosslinkable material in the pillars.   
     
     
         6 . The method of  claim 5  wherein the specific gravity of the first stage is matched with the specific gravity of the second stage to mitigate gravity effects. 
     
     
         7 . The method of  claim 5  wherein the crosslinkable material comprises a polysaccharide, and wherein the crosslinking agent comprises a source of borate or a polyvalent metal. 
     
     
         8 . The method of  claim 7  wherein one of the first and second stages comprises a pH control material to provide an alkaline pH and the other one of the first and second stages comprises the source of borate or polyvalent metal. 
     
     
         9 . The method of  claim 8  wherein the first stage comprises subproppant particles and has a slurry solids volume fraction (SVF) of 0.4 or more; and wherein the second stage is free of solids or has an SVF less than 0.4. 
     
     
         10 . The method of  claim 1 , further comprising:
 alternatingly injecting a plurality of pulsed first and second slugs of the well treatment fluid, wherein the first and second slugs each comprise a said stabilized slurry which may be the same or different;   wherein the slurry destabilizing system comprises a reagent selectively present in one of the first and second slugs to respectively form the pillars from consolidated proppant packs and the channels from relatively permeable proppant packs.   
     
     
         11 . The method of  claim 10  wherein the first and second slugs comprise a crosslinkable material and wherein the reagent comprises a solid particulated crosslinking agent. 
     
     
         12 . The method of  claim 10  wherein water and the reagent comprises a hydratable compound to remove water from at least one of the slurries. 
     
     
         13 . The method of  claim 10  wherein the stabilized slurries comprise water and the reagent comprises a superabsorbent polymer to remove water from at least one of the slurries. 
     
     
         14 . The method of  claim 1 , wherein the stabilized slurry is formed by at least one of: (1) introducing sufficient particles into the slurry to increase the solids volume fraction (SVF) of the slurry fluid to at least 0.4; (2) increasing a low-shear viscosity of the slurry to at least 1 Pa-s (5.11 s −1 , 25° C.); (3) increasing a yield stress of the slurry to at least 1 Pa; (4) increasing apparent viscosity of the slurry to at least 50 mPa-s (170 s −1 , 25° C.); (5) introducing a multimodal solids phase into the slurry; (6) introducing a solids phase having a packed volume fraction (PVF) greater than 0.7 into the slurry; (7) introducing into the slurry a viscosifier selected from viscoelastic surfactants and hydratable gelling agents; (8) introducing colloidal particles into the slurry; (9) reducing a particle-fluid density delta in the slurry to less than 1.6 g/mL; (10) introducing particles into the slurry having an aspect ratio of at least 6; (11) introducing ciliated or coated proppant into the slurry; and (12) combinations thereof. 
     
     
         15 . A propped fracture system obtained as a result of placing a proppant pack into a fracture according to a method comprising:
 injecting a well treatment fluid through a wellbore into a fracture in a subterranean formation, wherein at least a portion of the well treatment fluid comprises a proppant-containing stage, wherein at least a portion of the well treatment fluid comprises a stabilized slurry stage and wherein the proppant-containing and stabilized slurry portions may be the same or different;   injecting a destabilizing system into the fracture with the well treatment fluid to destabilize the slurry stage and form regions of consolidated proppant from the destabilized slurry stage; and   placing a plurality of proppant clusters forming pillars from the consolidated proppant regions spaced apart by fluid flow channels from the formation through the fracture toward the wellbore.   
     
     
         16 . A system for fracturing a subterranean formation, comprising:
 a supply module to inject a well treatment fluid through a wellbore into a fracture in a subterranean formation, wherein at least a portion of the well treatment fluid comprises a proppant-containing stage fluid, wherein at least a portion of the well treatment fluid comprises a stabilized slurry stage fluid and wherein the proppant-containing and stabilized slurry portions may be the same or different fluids; and   a destabilizing system in communication with the supply module for injection into the fracture with the well treatment fluid to destabilize the slurry stage fluid, form regions of consolidated proppant from the destabilized slurry stage fluid and form pillars spaced apart by fluid flow channels from the formation through the fracture toward the wellbore.   
     
     
         17 . The system of  claim 16  wherein the stabilized slurry comprises a liquid phase, and wherein the slurry destabilizing system comprises a liquid-removing agent to remove fluid from the stabilized slurry. 
     
     
         18 . The system of  claim 16 , further comprising:
 a pump system to sequentially inject a first stage of the treatment fluid into the formation followed by a second stage of the treatment fluid, wherein the first stage treatment fluid has a higher viscosity relative to the second stage treatment fluid, or wherein the first and second stages have different specific gravities, to initiate viscous fingering;   wherein the stabilized slurry comprises the proppant in the first stage fluid;   wherein the destabilizing system comprises a crosslinkable material in the first stage fluid, and a crosslinking agent in at least one of the first and second stage fluids to crosslink the crosslinkable material in the pillars.   
     
     
         19 . The system of  claim 18  wherein the crosslinkable material comprises a polysaccharide, and wherein the crosslinking agent comprises a source of borate or a polyvalent metal. 
     
     
         20 . The system of  claim 19  wherein one of the first and second stage fluids comprises a pH control material to provide an alkaline pH and the other one of the first and second stage fluids comprises the source of borate or polyvalent metal. 
     
     
         21 . The system of  claim 20  wherein the stabilized slurry comprises the proppant and subproppant particles, has a solids volume fraction (SVF) of 0.6 or more and solids comprising a packed volume fraction (PVF) of 0.7 or more; and wherein the second stage fluid is free of solids or has an SVF less than 0.05. 
     
     
         22 . The system of  claim 16 , further comprising:
 a pump system to alternatingly inject a plurality of pulsed first and second slugs of the treatment fluid, wherein the first and second slugs each comprise a said stabilized slurry;   wherein the slurry destabilizing system comprises a primary reagent selectively present in one of the first and second slugs to respectively form the pillars from consolidated proppant packs and the channels from relatively permeable proppant packs.   
     
     
         23 . The system of  claim 22  wherein the first and second slugs comprise a crosslinkable material and wherein the reagent comprises a solid particulated crosslinking agent. 
     
     
         24 . The system of  claim 23  wherein the stabilized slurries comprise a liquid phase, and wherein the reagent comprises a solid liquid-removal agent to remove fluid from the stabilized slurry. 
     
     
         25 . The system of  claim 16 , wherein the stabilized slurry comprises at least one of the stability indicia selected from: (1) a solids volume fraction (SVF) of at least 0.4; (2) a low-shear viscosity of at least 1 Pa-s (5.11 s −1 , 25° C.); (3) a yield stress of at least 1 Pa; (4) an apparent viscosity of at least 50 mPa-s (170 s −1 , 25° C.); (5) a multimodal solids phase; (6) a solids phase having a packed volume fraction (PVF) greater than 0.7; (7) a viscosifier selected from viscoelastic surfactants, in an amount ranging from 0.01 up to 7.2 g/L (60 ppt), and hydratable gelling agents in an amount ranging from 0.01 up to 4.8 g/L (40 ppt) based, on the volume of fluid phase; (8) colloidal particles; (9) a particle-fluid density delta less than 1.6 g/mL; (10) particles having an aspect ratio of at least 6; (11) ciliated or coated proppant; and (12) combinations thereof.