Working fluids

Abstract

A method of recovering a hydrocarbon material from a subterranean formation comprises forming a working fluid comprising substantially solid particles and an at least partially gaseous base material, the substantially solid particles exhibiting a greater heat capacity than the at least partially gaseous base material. The working fluid is introduced into a subterranean formation containing a hydrocarbon material to heat and remove the hydrocarbon material from the subterranean formation. An additional method of recovering a hydrocarbon material from a subterranean formation, and a working fluid are also described.

1 . A working fluid, comprising:
 carbon dioxide gas; and   substantially solid particles dispersed and stabilized within the carbon dioxide gas, the substantially solid particles each formulated to remain substantially solid up to a temperature of at least about 350° C. and each independently having a heat capacity of greater than or equal to about 0.1 kJ/kg-K.   
     
     
         2 . The working fluid of  claim 1 , wherein the substantially solid particles each independently have a thermal conductivity of greater than or equal to about 50 W/m-K. 
     
     
         3 . The working fluid of  claim 1 , wherein at least some of the substantially solid particles comprise functional groups attached to surfaces thereof. 
     
     
         4 . The working fluid of  claim 1 , wherein the substantially solid particles comprise one or more of graphite, graphene, fullerenes, diamond, nanofibers, clay, inorganic material, an organo-silicon material, and metal. 
     
     
         5 . The working fluid of  claim 1 , wherein the substantially solid particles comprise graphene nanoparticles. 
     
     
         6 . The working fluid of  claim 1 , wherein the substantially solid particles comprise expanded, substantially solid particles exhibiting functional groups attached to surfaces thereof. 
     
     
         7 . The working fluid of  claim 1 , wherein the substantially solid particles comprise functionalized nanoparticles formulated to remain stably dispersed in the carbon dioxide gas at a temperature within a range of from about 100° C. to about 350° C. 
     
     
         8 . The working fluid of  claim 7 , wherein the functionalized nanoparticles have functional groups that impart the functionalized nanoparticles with surfactant characteristics. 
     
     
         9 . The working fluid of  claim 1 , wherein the substantially solid particles exhibit a surface area within a range of from about 300 m 2 /g to about 1800 m 2 /g. 
     
     
         10 . The working fluid of  claim 1 , wherein the working fluid comprises from about 0.05 percent by weight to about 20.0 percent by weight of the substantially solid particles. 
     
     
         11 . The working fluid of  claim 1 , wherein at least some of the substantially solid particles individually comprise a core of a first material at least partially surrounded by a shell of a second material. 
     
     
         12 . A working fluid, comprising:
 carbon dioxide gas, and   discrete, composite nanoparticles having a heat capacity of greater than or equal to about 0.1 kJ/kg-K and thermal conductivity of greater than or equal to about 50 W/m-K dispersed and stabilized within the carbon dioxide gas, the discrete, composite nanoparticles each individually comprising:
 a core comprising a first material; and 
 a shell comprising a second, different material completely encapsulating the core. 
   
     
     
         13 . The working fluid of  claim 12 , wherein the heat capacity of the core is higher than the heat capacity of the shell. 
     
     
         14 . The working fluid of  claim 12 , wherein the heat capacity of the core is less than the heat capacity of the shell. 
     
     
         15 . The working fluid of  claim 12 , wherein at least some of the discrete, composite nanoparticles individually further comprise organophilic functional groups attached to surfaces of the shell. 
     
     
         16 . The working fluid of  claim 15 , wherein the at least some discrete, composite nanoparticles each individually exhibit from about 1 organophilic functional group per 5 surface atoms of the shell to about 1 organophilic functional group per 100 surface atoms of the shell. 
     
     
         17 . The working fluid of  claim 15 , wherein the organophilic functional groups are attached to the shell of each of the discrete, composite nanoparticles through intermediate functional groups. 
     
     
         18 . A working fluid, comprising:
 carbon dioxide gas; and   organophilic, solid nanoparticles within the carbon dioxide gas, the organophilic, solid nanoparticles each having a heat capacity of greater than or equal to about 0.1 kJ/kg-K and each formulated to remain stably dispersed in the carbon dioxide gas within a temperature range of from about 100° C. to about 350° C.   
     
     
         19 . The working fluid of  claim 18 , wherein the organophilic, solid nanoparticles each have a thermal conductivity within a range of from about 150 W/m-K to about 700 W/m-K. 
     
     
         20 . The working fluid of  claim 18 , wherein the organophilic, solid nanoparticles comprise one or more of functionalized graphite nanoparticles, functionalized graphene nanoparticles, functionalized fullerene nanoparticles, and functionalize carbon nanotubes.