The World's First Successful Implementation of Solid Fluidization Well Testing and Production for Non-Diagenetic Natural Gas Hydrate Buried in Shallow Layer in Deep Water

Abstract Based on the characteristics of shallow buried, non-trap structure and close cover, non-diagenesis, weak cementation and easy fragmentation of natural gas hydrate deposits in China, a solid fluidization well testing and production scheme to develop these kind of natural gas hydrate is proposed. The main idea is to transfer the non-diagenetic natural gas hydrate sediments buried in shallow layer of deep-water into a closed multi-phase transporting and lifting system through mechanical crushing fluidization, during the lifting riser system from seabed to surface, hydrate will be dissociated gradually based natural rule of sea water temperature rising and the hydrostatic pressure decrease with the change of water depth during the lifting process, to turn the uncontrollable decomposition process of non-diagenetic hydrate into controllable, and to achieve safe field exploitation of natural gas hydrate in the surface and shallow layer of deep-water. After the validity was verified by the laboratory experimental study, CNOOC successfully implemented the world's first solid fluidization well testing and production of marine non-diagenetic hydrate with the water depth of 1310m and the hydrate sediments layers 117~196m depth in May 2017. It means China has found an innovation way about natural gas hydrate exploration and development with self-developed key technology and tools. The implementation relied on the Deepwater Engineering & Survey Vessel "HYSY708" at the station of Li Wan 3 in the South China Sea and it was supported by fully self-developed technology, process and facilities.