System and method to fracture and seal subterranean formations

Abstract

A method for storing fluids and energy underground in a subterranean zone in one or more fractures created with a fracture and seal process utilizing different fluid systems having different fluid densities, viscosities, and gelation characteristics.

What is claimed is: 
     
         1 . A system for sealing a subterranean zone storing high pressure fluid, the system comprising:
 a subterranean zone having one or more propagating fracture tips;   a first fluid having a first density and a first viscosity;   a second fluid having a second density and a second viscosity;   said first density and said second density being generally equal, and said first viscosity less than said second viscosity; and   a facility to pump said first fluid and said second fluid from a wellbore into said zone whereby said second fluid displaces said first fluid to seal said tips.   
     
     
         2 . The system as defined by  claim 1  wherein said second fluid is a polysaccharide. 
     
     
         3 . The system as defined by  claim 1  wherein said first fluid is a water-based specialty polymer gel. 
     
     
         4 . The system as defined by  claim 1  wherein said first fluid is a silicone rubber containing polymers. 
     
     
         5 . The system as defined by  claims 3 or 4  wherein said first fluid contains a neat material. 
     
     
         6 . The system as defined by  claims 3 or 4  wherein said first fluid contains microfines. 
     
     
         7 . The system as defined in  claims 3 or 4  wherein said first fluid contains macro solids. 
     
     
         8 . The system as defined by  claim 1  whereby said facility further pumps said first fluid and said second fluid inside a rock formation within said zone. 
     
     
         9 . The system as defined by  claim 1  wherein said sealing fluid holds pressure in one direction. 
     
     
         10 . A method for sealing a subterranean zone storing high pressure fluid, the method comprising:
 selecting a subterranean zone for high pressure fluid storage;   fracturing said zone and creating fracture tips within said zone;   providing a first fluid having a first density and a first viscosity;   providing a second fluid having a second density generally equal to said first density, and a second viscosity greater than said first viscosity;   pumping said first and second fluid into said zone;   displacing said first fluid; and   sealing said tips.   
     
     
         11 . The method as defined by  claim 10  further comprising pumping said sealing fluid inside a rock formation within said zone. 
     
     
         12 . The method as defined by  claim 10  further comprising holding pressure from one side of said seal. 
     
     
         13 . A system for sealing a subterranean zone storing high pressure fluid, the system comprising:
 a subterranean zone having rock faces and fracture tips;   a first fluid having a first density, a first viscosity and a first shear rate;   a second fluid having a second density, a second viscosity and a second shear rate;   said first density and said second density being generally equal or said first density greater than said second density, and said first viscosity less than said second viscosity at any shear rate; and   a facility to pump said first fluid and said second fluid from a surface through a well and into said zone to seal said rock faces or said tips.   
     
     
         14 . The system as defined in  claim 13  wherein said first fluid is a sealing fluid. 
     
     
         15 . The system as defined in  claim 13  wherein said second fluid is a push fluid. 
     
     
         16 . The system as defined in  claim 13  wherein the system gathers geothermal energy from the rock after said zone is sealed. 
     
     
         17 . The system as defined in  claim 16  wherein said energy is stored for a predetermined period of time. 
     
     
         18 . The system as defined in  claim 17  wherein said stored energy is converted to perform useful work. 
     
     
         19 . The system as defined in  claim 18  wherein said work generates electricity. 
     
     
         20 . A system for sealing a subterranean zone storing high pressure fluid used for energy storage, the system comprising:
 a subterranean zone having rock faces and fracture tips;   a first fluid having a first density, a first viscosity and a first shear rate;   a second fluid having a second density, a second viscosity and a second shear rate;   said first density and said second density being generally equal or said first density greater than said second density, and said first viscosity less than said second viscosity at any shear rate;   a facility to pump said first fluid and said second fluid from a surface through a well and into said zone to hydraulically fracture and seal said rock faces or said tips; and   whereby the system gathers thermal energy from said rock wherein said energy is used to perform useful work at said surface.