南海琼东南盆地天然气水合物稳定域分布特征及资源预测

DISTRIBUTION OF GAS HYDRATE STABLE ZONES AND RESOURCE PREDICTION IN THE QIONGDONGNAN BASIN OF THE SOUTH CHINA SEA

琼东南盆地油气地质显示盆地内具有生物成因和热成因天然气的巨大生成能力和远景 .地震剖面显示盆地内发育有泥底辟和气烟囱、沟通泥底辟和气烟囱与海底的断裂及可能正在活动的天然气冷泉 ,这些特征非常有利于天然气水合物的发育 .通过天然气水合物热力学稳定域预测 ,确定了琼东南盆地天然气水合物的平面和剖面分布特征 .生物成因甲烷水合物分布于水深大于约 6 0 0m的海底 ,稳定带最大厚度约 31 4m ;热成因天然气水合物分布于水深大于约 4 5 0m的海区 ,稳定带最大厚度约 4 1 0m .盆地内天然气水合物远景总量约 1 0× 1 0 9m3,水合物天然气远景为 1 .6× 1 0 1 2 m3.

Oil and gas prospecting in the Qiongdongnan basin of the South China Sea indicates the potential of plenitudinous natural gases. Seismic sections show the occurrences of diapirs and gas filled zones that are communicated with seafloor through faults. The blur zones near seafloor on seismic section may suggest gas plumes in seawater. These characteristics are comparatively propitious to hydrate occurrence. A profile of gas hydrate stable zones across the basin slope is constructed by using thermodynamic prediction. Biogenic methane hydrates occur probably in the subsurface where water depth is larger than ～600m with ～310m of the maximum thickness, and thermogenic gas hydrates occur possibly on the subsurface where water depth is larger than ～450m with ～410m of the maximum thickness. The gas hydrate of ～10×10 9m 3, and the hydrate gas of ～1.65×10 12 m 3 are estimated in the Qiongdongnan basin of the South China Sea.