Thermal analysis for gas storage in salt cavern based on an improved heat transfer model

Abstract

Oversimplification of the heat transfer mechanism and assumption of uniform temperature and pressure in the salt cavern could cause significant errors when modeling temperature fields. This work proposed a coupled transient flow and heat transfer model for gas storage in the underground salt cavern to reflect the thermal behaviors between gas and surrounding rock, particularly the gas Joule-Thomson effect during gas operation. Then, a fully coupled numerical solution method based on a unified matrix is presented. An average error of 3.26% was observed between the model and field data quoted in literature. The case study indicates that during the gas withdrawal period, the maximum temperature difference in the salt cavern can reach 14.94 °C, while the temperature drop of the cavity wall is only about 4.07 °C, which is quite different from the traditional assumption. A special focus was given to the gas withdrawal rate, which seemed to have the most significant influence on the evolution of the temperature field in the salt cavern. Compared with the gas withdrawal rate of 35 m3/s, reducing the gas withdrawal rate to 20 m3/s can increase the minimum temperature by approximately 23.41%. This study could add further insights into the thermal performance during gas operation in the salt cavern and help to reveal the evolution of the temperature field in the cavity and surrounding rock.