Solution mining under an inert gas

Abstract

This method includes providing an cased borehole located within a salt bed, injecting an aqueous liquid into the cased borehole at a first pressure, in order to expose the salt bed to the aqueous liquid, thereby dissolving at least a portion of the salt bed and forming a brine solution within an underground storage volume, withdrawing at least a portion of the brine solution from the underground storage volume, and injecting an inert gas into the cased borehole at a second pressure, in order to provide an inert blanket within the underground storage volume, wherein the second pressure is greater than the first pressure but less than the maximum allowable pressure of the cavern.

1 . A method for solution mining comprising:
 producing a stable salt cavern within a salt bed by providing a cased borehole located within the salt bed,   injecting an aqueous liquid into the cased borehole at a first pressure, in order to expose the salt bed to the aqueous liquid, thereby dissolving at least a portion of the salt bed and forming a brine solution within the stable salt cavern, wherein said underground storage volume comprises a maximum allowable pressure,   withdrawing at least a portion of the brine solution from the stable salt cavern, and   injecting an inert gas into the cased borehole at a second pressure, in order to provide an inert blanket within the stable salt cavern, wherein the second pressure is greater than the first pressure but less than the maximum allowable pressure of the stable salt cavern,   
       wherein the maximum allowable pressure (P max ) is defined as P max <D casing ×G max , wherein G max =0.85 and D casing  is the death of a final cemented cashing shoe which defines a practical endpoint of a length of casing, permanently cemented into surrounding rock formations. 
     
     
         2 . The method of  claim 1 , wherein the inert gas is selected from the group consisting of nitrogen, helium, and argon. 
     
     
         3 . The method of  claim 1 , wherein the inert gas is nitrogen. 
     
     
         4 .- 6 . (canceled)