Research on Terrain Monitoring Device of Natural Gas Hydrate Trial Production Area in the Sea

As an important green energy source for the future, deep-sea natural gas hydrate has attracted worldwide attention in recent years, and several trial exploitations have been carried out. Hydrates are prone to decomposition leading to terrain subsidence; hence, there is an urgent need to monitor terrain change during the exploration. In this study, a monitoring device based on six-axis MicroElectro-Mechanical System array is developed to monitor the terrain subsidence during production of gas hydrate. The liability of the device has been tested both by lab experiments and a sea trial in the "Shenhu" area of the South China Sea with water-depth of 1,203 m. The device performed in-situ monitoring for 193 consecutive days; the deformation of the seafloor terrain has been successfully measured, and the seafloor topography has been obtained and reconstructed, showing that the overall average uplift of the seafloor terrain is 0.82 cm, with a maximum uplift of 5.98 cm and a maximum subsidence of 3.21 cm. The result shows that the geological conditions in the "Shenhu" area are stable, which provide a reference for the development of hydrates.