Geothermal investigation of the thickness of gas hydrate stability zone in the north continental margin of the South China Sea

摘要

The exploration of unconventional and/or new energy resources has become the focus of energy research worldwide, given the shortage of fossil fuels. As a potential energy resource, gas hydrate exists only in the environment of high pressure and low temperature, mainly distributing in the sediments of the seafloor in the continental margins and the permafrost zones in land. The accurate determination of the thickness of gas hydrate stability zone is essential yet challenging in the assessment of the exploitation potential. The majority of previous studies obtain this thickness by detecting the bottom simulating reflectors (BSRs) layer on the seismic profiles. The phase equilibrium between gas hydrate stable state with its temperature and pressure provides an opportunity to derive the thickness with the geothermal method. Based on the latest geothermal dataset, we calculated the thickness of the gas hydrate stability zone (GHSZ) in the north continental margin of the South China Sea. Our results indicate that the thicknesses of gas hydrate stability zone vary greatly in different areas of the northern margin of the South China Sea. The thickness mainly concentrates on 200–300 m and distributes in the southwestern and eastern areas with belt-like shape. We further confirmed a certain relationship between the GHSZ thickness and factors such as heat flow and water depth. The thickness of gas hydrate stability zone is found to be large where the heat flow is relatively low. The GHSZ thickness increases with the increase of the water depth, but it tends to stay steady when the water depth deeper than 3000 m. The findings would improve the assessment of gas hydrate resource potential in the South China Sea.