Pillar stability in underground salt cavern gas storage based on reliability theory

Unlike traditional methods that cannot qualify the reliability of gas storage, this paper presents a new method to analyze the reliability of pillar in salt cavern gas storage by Monte Carlo sampling after establishing the failure function based on the Molar-Coulomb criterion. The new method is used to calculate the reliability indicator and failure probability of pillar in a salt cavern gas storage in China. The results show that the failure probability increases with the increase of cavern depth and interlayer number, and decreases with the increase of internal pressure and pillar width. The width has the greatest influence on the pillar reliability. Therefore, the pillar width divided by the diameter of salt cavern (span ratio) should be greater than 2 if practical provided that the maximum capacity is maintained. It is recommended that high quality and low-buried salt rocks with less interlayers are used to build salt cavern storage. Operation at higher pressure is preferred for the gas storage, and the time of operation at low-pressure should be minimized.