东海陆坡及相邻槽底天然气水合物的稳定域分析

THE STABILITY ZONE OF GAS HYDRATE IN THE SLOPE OF EAST CHINA SEA AND NEIGHBORING TROUGH BASIN AREA

利用实测的海底温度和海底热流资料对东海陆坡和冲绳海槽中轴以西的槽底地区的海底温度场和热流场进行了分析 .利用地震声纳浮标和OBS(OceanBottomSeismometer)资料将本研究区的地层划分为 6层 ,自上而下地层的速度分别为 1.8(1.8～ 2 .2 )km s、2 .2 (2 .0～ 2 .5 )km s、2 .8(2 .7～ 3.2 )km s、3.4～ 3.6km s、4 .2 (4 .1～ 4 .7)km s、5 .1km s.上部的 1.8～ 2 .2km s的速度层相当于第四纪的地层 ,2 .8km s的速度层相当于上新世上部的地层 ,3.4～4 .2km s的速度层相当于上新世下部的地层 .天然气水合物稳定域覆盖的面积从水深约 5 0 0m的陆坡下缘到冲绳海槽的中轴部分约 70 0 0 0km2 ,相当于整个东海海域面积的十分之一 .稳定带的厚度从 4 0 0m(研究区中部 )到 110 0m(研究区北部和南部 )不等 .适合水合物稳定赋存的地层主要是第四纪 (1.8km s、2 .2km s)和上新世的地层(2 .8km s) .根据热流、构造活动性和稳定带的厚度分析 ,研究区北部和南部更适合天然气水合物的稳定赋存 .

We analyze the distribution of temperature and heat flow of the sea floor sediment in the area of East China Sea slope and West basin area of the Okinawa Trough. Based on the Sonar Buoy and OBS data, 6 velocity layers are recognized, each of which has velocity of 1.8(1.8～2.2) km/s,2.2(2.0～2.5)km/s,2.8(2.7～3.2)km/s,3.4～3.6km/s,4.2(4.1～4.7)km/s and 5.1km/s,respectively.The upper velocity layer of 1.8～2.2 km/s corresponds to the Quaternary sediment stratum. The layer with velocity 3.4～4.2km/s is the Pliocene sediment stratum. The area that is suitable for stable existence of gas hydrate by the temperature and pressure is 70,000km2 about 1/10 the total area of East China Sea. The thickness of the stability zone ranges from 400m (Middle Part of Okinawa Trough) to 1100m (North and South Part of Okinawa Trough). The Quaternary and Pliocene layers are suitable for stable exitence of gas hydrate. According to the tectonic stability and heat flow, the north part and south part of the Okinawa Trough are the most perspective area for the gas hydrate explorations.