Feasibility Study on Transformation of Abandoned Salt Caverns into Underground Gas Storage in China
Authors: Bai Song , Ding Guosheng , Wanyan Qiqi , Li Kang , Li Haitao 
Published: September 2022

ABSTRACT:
The transformation of abandoned salt caverns from salt-production industries into Underground Gas Storages(UGS) has a great significance for the full utilization of salt mine resources and accelerating the construction of UGS. The abandoned salt caverns can save a lot of construction time for gas storage and obtain faster gas injection-production application and economic effect. At the same time, this work can reduce the complex safety risks such as brine leakage, land subsidence and collapse caused by the long-term deformation of the cavern. In China, it has a long history of salt production, widely distributed salt mines, and a large number of abandoned cavities, which provide a basis for the transformation. Combined with the experience of transforming abandoned single-well cavities into gas storages in Jintan city, Jiangsu Province, this paper mainly studies the feasibility of utilization and transformation of abandoned salt cavern mined by directional butted wells in Pingdingshan city, Henan province, from the perspective of geology, engineering and economy. The results of sonar cavity measurement show that the old caverns have a single cavity volume of 300000 ~ 450000 m3, which provides big storage volume for the reconstructed salt cavern gas storage. Moreover, combined with the borehole sealing test results, the cavity well type transformation scheme of "plugging old wells and drilling renewal wells" is proposed, which has been successfully applied in directionally butted-well M5/M6. This study provides rich experience and reference for the reuse of abandoned salt cavern with directional butt wells for underground gas storages.

1. INTRODUCTION
In recent decades, natural gas as a clean and efficient energy, makes an increasely important contribution to the national economy and social development, and the demand growth significantly more than coal and oil (Wang et al., 2021). Limited by exploration and development technology, China’s current natural gas recovery is not enough to meet its own consumption, and some of it needs to rely on imports. In addition, natural gas is mainly used for residents living and industrial gas, which is significantly affected by seasons and market prices, so it is necessary to be stored in advance (Jiang et al., 2021). Among the existing storage facilities, salt cavern underground gas storage has greater advantages with the characteristics of high injection-production efficiency, low cushion gas .volume, safety and flexibility (Pamucar et al., 2020; Pinto et al., 2021). Some foreign countries such as United States, Germany and Russia, used the thick salt formation to build UGS very early, and have experienced decades of development and accumulated rich experience in cavity construction. Although China started late, it has also experienced more than ten years of development since the first salt cavern gas storage (Jintan UGS in Jiangsu province) was built in 2006 (Yang et al., 2017). At present, about 110 salt cavern underground gas storages have been built all over the world.