Surrounding rock stability of horizontal cavern reconstructed for gas storage

Abstract

Rock salt is recognized in the world to be an ideal medium for storing oil and natural gas. There are a lot of dissolved caverns formed by salt extraction in China which are mainly divided into horizontal caverns and pear-shaped caverns, among which the number of old horizontal caverns is the largest. However, the existing old horizontal caverns cannot be directly used to store oil and natural gas and need to be reconstructed. The method of drilling new wells outside the caverns to reconstruct the horizontal old caverns was introduced first; Then the possible influence factors of surrounding rock stability in horizontal caverns reconstruction were discussed by using mechanics theories; Finally, the influence of drilling new wells outside the caverns on the stability of surrounding rock of horizontal old caverns and the salt roof was obtained by numerical simulation, including the volume shrinkage rate of the reconstructed horizontal caverns, the plastic zone and displacement distribution of surrounding rock and salt layer roof. The results of theoretical analysis and numerical simulation show that the volume of the new drilling caverns, the distance between the new drilling cavern and the old cavern, the internal pressure during gas storage, and the operation time of storage are the main factors affecting the stability of the surrounding rock of the horizontal cavern and its salt layer roof, which indirectly determines whether the horizontal old cavern can be successfully reconstructed into gas storage.