Horizontal natural gas caverns in thin-bedded rock salt formations

Natural gas storage caverns are usually built either in a rock salt dome or in a bedded rock salt formation. In China, the rock salt stratum has the following characteristics: thin, inter-layered, bedded and highly impure. The height of a cavern in bedded rock salt deposit in China depends largely on the thickness of the salt formation (80–300 m) and is much smaller than in thick domes and thick layers of rock salt deposits in Europe and the USA, where a storage cavern is typically, cylindrically shaped. This renders the diameter of a bedded salt cavern in China to be greater than its height to obtain sufficient storage volume. The stability of horizontal salt caverns with different diameters and varied minimal internal pressures during its long-term operation was numerically analyzed in this paper regarding convergence, damage, stress to peak or dilatancy strength ratio and effective strain. The Hou/Lux constitutive model including some relevant parameters from previous laboratory investigations were used for the numerical simulations. The simulation results show that a horizontal cavern (height ≪ length) for underground gas storage is more efficient, profitable and suitable because of its few times larger storage capacity than the most used vertical cavern (height ≫ diameter) or a prolate cavern (height ≈ or < diameter) under the Chinese special geological condition of thin-bedded rock salt deposits, provided with appropriate construction and operation parameters.