A Review of Potential Geological Hazards and Precautions in the Mining of Submarine Natural Gas Hydrate

Natural gas hydrate (NGH hereafter), commonly known as combustible ice ((CH₄)n·mH₂O), is an abundant non-conventional clean energy resource. It is mainly located in permafrost areas and submarine sediment layers at depths of 0–200 m and 300~3000 m underwater. Submarine NGH accounts for about 97%. Its commercial mining may be a solution to mankind’s future energy problems, as well as the beginning of a series of geological risks. These risks can be divided into two categories: natural geological hazards and secondary geological accidents. Based on the viewpoints of Earth system science researchers, this paper discusses the main potential geo-hazards of submarine NGH mining: stratum subsidence, seafloor landslides, the greenhouse effect, sand piping, well blowout, and wellbore instability. To minimize the potential catastrophic impacts on the Earth’s ecosystem or mechanical accidents, corresponding technical precautions and policy suggestions have been put forward. Hopefully, this paper will provide a useful reference for the commercial mining of NGH.