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 that is greater than the first pressure but less than the maximum allowable pressure of the cavern.

What is claimed is: 
     
         1 . A method for solution mining comprising;
 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,   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 that is greater than the first pressure but less than the maximum allowable pressure of the cavern.   
     
     
         2 . The method of  claim 1 , wherein the inert gas selected from the group consisting of nitrogen, helium, and argon. 
     
     
         3 . The method of  claim 1 , wherein the inert gas is nitrogen. 
     
     
         4 . 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 ), wherein the maximum allowable pressure (P max ) is defined as P max <D casing ×G max , wherein G max =0.85. 
     
     
         5 . 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 ), wherein the maximum allowable pressure (P max ) is defined as P max <D casing ×G max , wherein G max =0.8. 
     
     
         6 . The method of  claim 1 , wherein the inert blanket has a blanket depth, and the blanket depth is measured by means of a wire line density test.