Development of Marine Natural Gas Hydrate Mining Technology and Equipment

TLDR: In this paper, the authors focus on existing hydrate exploitation method and analyze key technologies and processes involved in two trial production modes (i.e., depressurization and solid-state fluidization).

Abstract: Natural gas hydrate (NGH), especially marine NGH, is a new source of clean unconventional energy, and it is expected to replace traditional fossil fuels. There are high global reserves of NGH. However, its exploitation is still in the research stage because commercial large-scale exploitation is hindered by challenges with respect to technology and equipment. In this study, we focus on existing hydrate exploitation method and analyze key technologies and processes involved in two trial production modes (i.e., depressurization and solid-state fluidization). These processes were adopted in the pilot production projects of offshore natural gas in Japan and China. In the study, we summarize the development status of relevant technology and equipment in China and across the world and also propose development suggestions for marine gas hydrate exploitation, which are suitable for reservoir and equipment technology in China. The results of the study indicate that China lags behind other countries with respect to key technologies and equipment for hydrate, oil gas, and subsea metal mining (i.e., deep-sea mining vehicles and dual-gradient drilling technology for loose shallow layers). In the field of special key technologies and equipment (i.e., sand control technology and equipment, pre-inclined directional drilling technology for shallow hydrate-mining, and combined production of hydrate, free gas, and conventional natural gas), China’s technology has advanced to an international level. Nevertheless, the advancement does not satisfy the requirements of commercial mining. The development of exploitation technologies and equipment for marine NGHs in China is expected to enter a leading stage in 2035, and the establishment of an engineering equipment system for commercial development is expected. Hence, we recommend the development of a research and development plan for marine NGH exploitation technology and equipment at the national level to promote the commercial development of hydrates. Furthermore, this is necessary to accelerate research and application of special and general technologies and equipment for offshore non-diagenetic hydrate exploitation.