To provide a safer and cost effective solution, a new concept of storing liquefied natural gas (LNG) in a lined rock cavern with containment system has been developed. It consists of protecting the host rock against the extremely low temperature and providing a liquid and gas tight steel liner. Moreover, the moderated and controlled frost development in the surrounded rock mass contributes to creating an ice ring, which acts as a secondary barrier against any possible leakage. To demonstrate the feasibility of this concept and to validate the numerical modeling and calculations, a pilot plant was constructed at KIGAM in the Daejeon Science Complex in 2003, which had been under operation for storing LN2 (Boiling Temperature: −196°C) since January 2004, and now been decommissioned. In this paper, measured in-situ rock mass responses from the operation of Daejeon LNG storage pilot cavern are presented and analyzed on rock mechanical point of view. The obtained results from the pilot test confirmed that both construction and operation of underground LNG storage in lined rock caverns are technically feasible. The Daejeon LNG storage pilot cavern represents a further important step in the validation of the technology of underground LNG storage in the lined rock caverns.
To provide a safe and cost-effective solution, a new concept of storing LNG in a lined hard rock cavern (LRC) has been jointly developed by Geostock, SKEC and SNTechnigaz with the help of KIGAM. The basic concept is based on the combination of a containment system to ensure for LNG with rock protection against thermal shock and a drainage system during the early months of the storage operation and before the freezing of the surrounding rock. It consists of protecting the host rock against the extremely low temperature by using a containment system with gas-tight steel liners and insulation panels as illustrated in Figure 1.
In order to verify the technical feasibility of such a storage concept, a pilot plant was constructed in 2003 and had been operated by storing liquid nitrogen (LN2, Boiling Temperature: −196°C) since from January through August, 2004. The cavern has, more recently, been decommissioned. The pilot cavern is located in Daejeon, about 200 km south from Seoul, in an existing research cavern implemented within the KIGAM research facilities. Figure 2 shows a bird's-eyeviewof the pilot cavern for LNG storage.The rock type around the cavern mainly consists of fresh granite with RQD of 80–86 and with the most frequent Q value of 12.5. Therefore, it is proper to adapt rock bolting to stabilize main cracks of the existing cavern and ensure the stability of possible crack position. The access to the pilot cavern was provided through an existing horizontal tunnel and the cavern roof lies at a depth of about 20m below the ground.
