Review on 20 years' UGS construction in China and the prospect

Underground gas storage (UGS) is one important part of natural gas supply chain, and it plays an important role in the peak shaving, security and supply support of natural gas in China. In this paper, the 20 years' development history of China's UGSs from zero to large-scale industry was reviewed with the overall construction of the Dazhangtuo UGS of the Dagang Oilfield in 1999 as a mark. In this period, 27 UGSs were built up with the peak shaving capacity more than 100×10⁸ m³, over 100 invention patents and over 20 software copyrights were authorized, 15 standards were formulated and over 20 monographs were issued. Then, the technological innovation achievements obtained in the UGS construction in China were mainly described, including 10 typical technological achievements, e.g. the UGS site selection mode and evaluation technology in the situations with complex fault block, complex fluid, complex lithology and strong-heterogeneity deep reservoir, the evaluation technology for the dynamic sealing performance of UGS trap with complex geological conditions, the drilling and completion technology with the ultralow-pressure lost circulation control and reservoir protection and the wellbore sealing under alternating stress as the core, the key technology and equipment for the surface injection and production at high pressure and large flow rate, and the "three-in-one" risk control system of UGS formation-wellbore-surface. Finally, based on China's 20 years of UGS construction experience and China's current industry policies, the opportunities and challenges of the future UGS development in China were clarified.