FLNG vessels under typhoon conditions in China sea areas

For solving the operation problems of floating liquefied natural gas (FLNG) vessels in harsh sea areas, especially in the areas where typhoon happens frequently, the characteristics of cyclone (typhoon) in China sea areas were analyzed based on the environmental conditions of the South China Sea. Then, the FLNG vessel connection operation and the FLNG vessel disconnection and evacuation plans in the situation of cyclones were compared. And finally, a series of research was carried out on the technical difficulties related to the FLNG vessel connection operation plan, such as the temperature field of LNG cofferdam, the vapor treatment and diffusion during a cyclone, such as a typhoon, and the typhoon generator at the shallow-water platform. Based on these analysis and research, the following recommendations were proposed. First, it is recommended to adopt the FLNG vessel connection operation plan during a typhoon to guarantee convenient and safe operation and to improve oil and gas field benefits. Second, a ballast cabin can be set inside the vessel to ensure the safety of Grade E steel in FLNG vessel, especially during a typhoon. Third, BOG diffusion can be still safe in the most dangerous working condition when the vent pipe reaches a certain height during a typhoon. Fourth, four groups of mooring systems (five pieces in each group) can be designed to guarantee the mooring strength of FLNG vessel connection operation during a typhoon. And fifth, when a typhoon arrives, it is necessary to stop FLNG production, release the pressure and organize personnel evacuation in a planned way. After the typhoon leaves, personnel return and FLNG production starts again. In this way, efficiency can be increased effectively, and the operational convenience and safety of FLNG vessels can be ensured.