Feasibility analysis of single well and double cavity in the salt-cavern gas storage with thick sandwiches

The salt rock formations in China are usually associated with thick sandwiches. Considering the geological conditions of the salt rocks with thick sandwiches, the solution mining mode of single well and double cavity is adopted. In this mode, thick sandwich is excluded from the storage building interval, and the salt layers above and below it are used for storage building, so as to improve the utilization ratio of salt rock resources and increase the effective gas storage space of single well. In this paper, the solution mining scheme of single well and double cavity was designed to carry out simulation prediction with the salt layers above and below the thick sandwich in Chuzhou Salt Mine as the cavity building targets. In addition, the engineering expense (drilling and cavity building included) of the solution mining scheme of single well and double cavity was estimated and compared with that of single well and single cavity. It is indicated that under the particular geological conditions, the effective volume achieved by the solution mining scheme of single well and double cavity is 27.8×10⁴ m³ and that achieved by the solution mining scheme of single well and single cavity is 18.0×10⁴ m³. It means that compared with the solution mining scheme of single well and single cavity, the solution mining scheme of single well and double cavity increases the effective volume by about 54.4% and the working gas volume by 41.5% and saves the cavity building investment per cubic meter by 21%. In conclusion, the solution mining mode of single well and double cavity is much more advantageous in gas storage spatial volume utilization and underground engineering investment per cubic meter, so its research, popularization and application shall be strengthened.