Hydrogen cavern pad gas management

Abstract

A method of pad gas management in an underground storage volume including storing a first compressible fluid, determining a transient minimum operating pressure (P trans ), measuring the pressure (P act ), removing at least a portion of the first compressible fluid, concurrently, introducing an incompressible fluid, thereby producing a transient pressure condition controlled by the flow rate of the incompressible fluid, such that P trans <P act . The method may also include a length of casing, permanently cemented into the surrounding rock formations, with a final cemented casing shoe defining the practical endpoint at an approximate depth (D casing ), determining a transient pressure gradient (G trans ) for the underground storage volume, wherein P trans <D casing ×G trans . The maximum removal of the first compressible fluid is controlled such that P min <P act , and wherein the transient pressure condition has a duration (D) of less than 7 days, more preferably less than 5 days.

What is claimed is: 
     
         1 . A method of pad gas management in an underground storage volume, comprising:
 storing a first compressible fluid in an underground storage volume,   determining a transient minimum operating pressure (P trans ) for said underground storage volume,   measuring the pressure (P act ), of said underground storage volume,   removing at least a portion of said first compressible fluid from said underground storage volume,   concurrently, introducing an incompressible fluid into said underground storage volume, thereby producing a transient pressure condition,   
       wherein the transient pressure condition is controlled by the flow rate of said incompressible fluid, such that P trans <P act . 
     
     
         2 . The method of  claim 1 , wherein said underground storage volume is an underground salt cavern. 
     
     
         3 . The method of  claim 1 , wherein said first compressible fluid is selected from the group consisting of nitrogen, air, carbon dioxide, hydrogen, helium, and argon. 
     
     
         4 . The method of  claim 3 , wherein said first compressible fluid is hydrogen. 
     
     
         5 . The method of  claim 1 , wherein said incompressible fluid is selected from the group consisting of brine, water, or water slurry. 
     
     
         6 . The method of  claim 1 , further comprising;
 a length of casing, permanently cemented into the surrounding rock formations, with a final cemented casing shoe defining the practical endpoint at an approximate depth (D casing ),   determining a transient pressure gradient (G trans ) for said underground storage volume,   
       wherein P trans <D casing ×G trans . 
     
     
         7 . The method of  claim 6 , wherein 0.2 psi/ft of depth<G trans <0.3 psi/ft of depth. 
     
     
         8 . The method of  claim 7 , wherein 0.25 psi/ft of depth<G min . 
     
     
         9 . The method of  claim 1 , wherein said incompressible fluid does not exceed a predetermined maximum flow rate (F max ). 
     
     
         10 . The method of  claim 9 , wherein F max  is 20 feet per second. 
     
     
         11 . A method of pad gas management in an underground storage volume, comprising:
 storing a first compressible fluid in an underground storage volume,   determining a transient minimum operating pressure (P trans ) for said underground storage volume,   measuring the pressure (P act ), of said underground storage volume,   removing at least a portion of said first compressible fluid from said underground storage volume,   
       wherein the maximum removal of said first compressible fluid is controlled such that P min <P act , and 
       wherein said transient pressure condition has a duration (D) of less than a predetermined period of time. 
     
     
         12 . The method of  claim 11 , wherein said underground storage volume is an underground salt cavern. 
     
     
         13 . The method of  claim 11 , wherein said first compressible fluid is selected from the group consisting of nitrogen, air, carbon dioxide, hydrogen, helium, and argon. 
     
     
         14 . The method of  claim 13 , wherein said first compressible fluid is hydrogen. 
     
     
         15 . The method of  claim 11 , further comprising;
 a length of casing, permanently cemented into the surrounding rock formations, with a final cemented casing shoe defining the practical endpoint at an approximate depth (D casing ),   determining a transient pressure gradient (G trans ) for said underground storage volume,   
       wherein P trans <D casing ×G trans . 
     
     
         16 . The method of  claim 15 , wherein 0.2 psi/ft of depth<G trans <0.3 psi/ft of depth. 
     
     
         17 . The method of  claim 16 , wherein 0.25 psi/ft of depth<G min . 
     
     
         18 . The method of  claim 11 , wherein D is less than 7 days. 
     
     
         19 . The method of  claim 18 , wherein D is less than 5 days.