Preliminary Risk Assessment (PRA) for Tests Planned in a Pilot Salt Cavern Hydrogen Storage in the Frame of the French Project STOPIL-H2

The STOPIL-H2 project, supported by the French Geodenergies research consortium, aims to design a demonstrator for underground hydrogen storage in cavern EZ53 of the Etrez gas storage (France), operated by Storengy. Two types of tests are planned in this cavern: a tightness test, with nitrogen and hydrogen, then a cycling test during which the upper part of the cavern (approximately 200 m3) will be filled with hydrogen during 6 to 9 months. In this paper, the PRA for the cycling test is presented comprising the identification of the major hazards and the proposed prevention and protection measures. The implemented methodology involves the following steps: data mining from the description of the project; analysis of lessons learned from accidents that occurred in underground gas storage and subface facilities; identification of the potential hazards pertaining to the storage process; analysis of external potential aggressors. Resulting as one of the outcomes of the PRA, major accidental scenarios are presented and classified according to concerned storage operation phases as well as determined preventive or protective barriers able to prevent their occurrence of mitigate their consequences.