关键词: 冲绳海槽, 天然气水合物, 发育, 水合物稳定带, 分布

Abstract: The appearance,distribution and depth of stable zones for the methane gas hydrate in the Okinawa trough are analyzed according to the geological conditions of Okinawa trough,the measured temperatures of bottom water, the measured geothermal gradients and the phase conditions of methane gas hydrate.The results suggest that the Okinawa trough is suitable for the formation of methane gas hydrate. In the northern district of the Okinawa trough,natural gas hydrate appears at the see depth over 600 meters,and the thickness of stable zone for gas hydrate is less than 50 meters.In the middle and southern parts,gas hydrate appears at the sea depth over 500 meters,and the responding thickness of stable zones ranges 25 to 115 meters and 90 to 365 meters,respectively.The stable zones of gas hydrate become thicker and thicker from the north Okinawa to south Okinawa and from the middle part of the trough to the two sides.These conclusions were obtained on the hypotheses of methane gas hydrate,seawater and measured geothermal gradients.If the hypotheses are changed,the natural gas hydrate in the Okinawa trough may be more abundant,and the thickness of stable zones will be greater than the data based on the hypotheses.

Key words: Okinawa trough, natural gas hydrate, development, stable zone, distribution