Solution mining a stable roof under an inert gas

Abstract

This method includes a solution mined underground salt cavern, wherein the salt cavern has a main body with a mean diameter of D N , and an upper portion comprising an inert gas pad, a stream of leaching water which is injected below the inert gas pad with a velocity V, thereby leaching an Nth tier adjacent to the upper portion having a height H 1 and a mean diameter D N+1 that is smaller than D N by a ratio R raising the inert gas pad by an amount A 1 , providing a stream of leaching water which is injected below the inert gas pad with a velocity V, thereby leaching a N+1th tier adjacent to the Nth tier having a height H 2 and a to a mean diameter D N+2 that is smaller than D N+1 by a ratio R, and repeating steps c and d a number of times T, thereby forming a stable roof.

What is claimed is: 
     
         1 . A method of solution mining a stable roof under an inert gas blanket, comprising:
 a) providing a solution mined underground salt cavern, wherein said salt cavern has a main body with a mean diameter of D N , and an upper portion comprising an inert gas pad,   b) providing a stream of leaching water which is injected below the inert gas pad with a velocity V, thereby leaching an Nth tier adjacent to the upper portion having a height H 1  and a mean diameter D N+1  that is smaller than D N  by a predetermined ratio R,   c) raising the inert gas pad by a predetermined amount A 1 ,   d) providing a stream of leaching water which is injected below the inert gas pad with a velocity V, thereby leaching a N+1th tier adjacent to the Nth tier having a height H 2  and a to a mean diameter D N+2  that is smaller than D N+1  by a predetermined ratio R,   e) repeating steps c and d a predetermined number of times T, thereby forming a stable roof.   
     
     
         2 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein the inert gas is selected from the group consisting of nitrogen, helium, argon, or methane. 
     
     
         3 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein the inert gas is nitrogen. 
     
     
         4 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein H 2  is between 10 and 50 feet. 
     
     
         5 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein H 2  is between 20 and 40 feet. 
     
     
         6 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein H 2  is 30 feet. 
     
     
         7 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein R is between 15% and 35%. 
     
     
         8 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein R is between 20% and 30%. 
     
     
         9 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein R is 25%. 
     
     
         10 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein V is between 5 feet/second and 9 feet per second. 
     
     
         11 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein V is between 6 feet/second and 7 feet/second. 
     
     
         12 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein the inert gas pad has a pressure, and a depth defined by the interface between the inert gas and a brine/water mixture produced by the solution mining, and wherein the inert gas pad depth is determined by monitoring the gas pad pressure. 
     
     
         13 . The method of solution mining a stable roof under an inert gas blanket of  claim 1 , wherein the inert gas pad has a depth defined by the interface between the inert gas and a brine/water mixture produced by the solution mining, and wherein the inert gas pad depth is verified by wire line density measurement at the interface.