Influence of natural gas thermodynamic characteristics on stability of salt cavern gas storage

Abstract

The good creep characteristics and damage repair characteristics of salt rock make it a high-quality stratum resource for the construction of underground natural gas storage. During the operation of salt cavern gas storage, the creep of salt rock is mainly concentrated in the steady creep stage. Stress and temperature have a great influence on the creep properties of salt rock. When the salt cavern gas storage is in operation, the injection and production cycle alternates, the gas flow is large in a short time, and the internal pressure and temperature of the salt rock cavern are constantly changing. The thermal and stress states of the gas storage are constantly changing, which directly affects the creep characteristics of the underground cavern of the gas storage, and thus affects the shape change of the cavern and the volume convergence characteristics. This paper is based on the characteristics of natural gas flow and heat transfer when the gas is injected and mined, through the fitting of experimental data and the application of classical creep constitutive equations, the characteristics of the cavern volume convergence during the ultimate gas recovery operation and emergency peaking operation of the gas storage are studied. The results showed that the temperature change in the gas storage cavern had a significant effect on the creep of salt rock. The influence of temperature should be considered when analyzing the stability of gas storage. The volume convergence of the cavern gas storage cavern is mainly concentrated in the large-rate gas production and low-pressure gas storage stages. Increasing the internal pressure and shortening the gas production running time have a significant inhibitory effect on the volume reduction of the cavern. While meeting the demand for natural gas, the emergency gas production time should be shortened as much as possible to avoid the long-term low-pressure gas storage state of the gas storage, which can meet the stability requirements of the salt rock cavern volume convergence.