The gas hydrate potential in the South China Sea

Based on the relationship among water depth, sea water temperature, geothermal gradient and geological setting, the gas hydrate potential in the South China Sea (SCS) is estimated. The thickness of the gas hydrate stability zone (GHSZ) and the minimum sea water depth in order to form the gas hydrate structures I (100% CH4), II (95.9% CH4) and H (90.4% CH4) are calculated and defined by the relationship among sea water depth, seawater temperature, geothermal gradient and gas composition. The average thickness of the GHSZ in the SCS is estimated to be 225 m, 270 m and 365 m for the gas hydrate structures I, II and H, respectively. The calculation also shows that the gas hydrate accumulation is at the water depth equal to or deeper than 600 m, 400 m and 300 for gas hydrate structures I, II and H, respectively. Maximum thickness area of the GHSZ in the SCS is also defined in the water depth ranging from 1200 to 2300 m. By assuming that gas hydrate is distributed in one third of the calculated GHSZ area, the volume of gas hydrate reservoir is estimated to contain 1.38 × 1014 m3, 1.41 × 1014 m3 and 1.7 1014 m3 of methane gas at the standard temperature and pressure (STP) for the gas hydrate structures I, II and H, respectively.