Simulation of injection/recovery thermo-dynamic performance for underground gas storages with salt caverns

Building underground gas storages with salt caverns are one of the most economic and reasonable ways to solve the imbalances of short-term gas consumption in cities essentially. During building and operation of gas storages, the gas in the solved chambers makes thermal exchange with the surrounding salt formation by natural inter-flow, and the transient thermo-conducting temperature field is formed with the surrounding walls of salt caverns. In the other hand, the continuous injection/recovery cycle makes the pressure and temperature of the chambers change. Especially during continuous gas recovery, the well-head pressure and temperature easily enter the dangerous range to generate hydrate since the Joule-Thomson effect of pressure drop. So it is very necessary to determine the injection/recovery thermo-dynamic performance for underground gas storages with salt caverns. According to the theories of thermodynamics, transfer calorific and hydrodynamics, aiming at the characteristics of gas flowing in the borehole and thermo-transferring process in the solved chambers during gas injection/recovery process, and regarding the borehole, solved chambers and surrounding salt formation as one integral system, the coupling mathematical models and solution methods are developed to describe the injection/recovery performance. Also, the corresponding numeral calculating software is developed. The software can predict the pressures and temperatures in the solved chambers and the top/bottom of the bore-hole for underground gas storages with salt caverns during continuous injection/recovery process, and identify the dangerous range to generate hydrate etc. The study is helpful to predict and analyze the construction and features of underground gas storages with salt caverns; guide the operation conditions and provide the theoretical ground for the optimized design of surface injection/recovery system.