南海北部陆坡天然气水合物研究进展

综合调查已揭示了一系列显示南海北部陆坡存在天然气水合物的地质、地球物理和地球化学指标。结果表明两类天然气水合物系统即低通量扩散型水合物和高通量渗漏型水合物共存于南海北部陆坡，特别是东沙海域和神狐海域。天然气水合物钻探航次获得的资料为进一步理解神狐海域和东沙海域的天然气水合物系统提供了基础。钻探结果证明强似海底反射往往与低饱和度的含天然气水合物沉积物薄层联系在一起；高饱和度的天然气水合物一般不需要与地震剖面上识别的似海底反射对应，而与气体渗漏和断裂构造等特征相关。地球化学资料显示神狐海域和东沙海域的天然气水合物气源主要为微生物成因气。神狐海域钻探证实的天然气水合物分布区具有160亿立方米的甲烷地质储量，在目前天然气水合物开采技术和工艺条件下，开采具有较大困难，有待于开发更为先进的技术。随钻测井资料显示东沙海域浅部存在中等-高饱和度水合物，而深部水合物稳定带底界上方存在低饱和度天然气水合物。南海北部陆坡天然气水合物有待于深入探究其赋存状态、饱和度、储层特性和资源前景。

Progress of Gas Hydrate Research in Northern South China Sea

Integrated investigation has revealed a number of geological, geophysical and geochemical indicators showing the presence of gas hydrate in the northern South China Sea (SCS). Both the distributed, low-flux gas hydrate system and the focused, high flux gas hydrate system coexist in the northern SCS, particularly in Dongsha Area and Shenhu Area. The available data collected in the drilling expeditions provide the basis for further understanding of the gas hydrate system in Shenhu Area and Dongsha Area. These drilling expeditions have documented that the strong bottom simulation reflectors (BSRs) always correspond to the low saturation of thin gas hydrate and highly saturated gas-hydrate deposits do not need to be linked to seismic identified BSRs. The geochemical data show that gas sources of hydrates are biogenic methane in Shenhu Area and Dongsha Area. Methane trapped in the drilling-confirmed Shenhu hydrate deposit is approximately 16 billion m3. However it is difficult to be produced by using the present technology. The Logging-While-Drilling data confirmed the presences of moderate-high saturations of gas hydrate in the shallow sediments and low saturations of gas hydrate in the deep sediments above the bottom of gas hydrate stabilization zone. States, concentration, characteristics and resource prospective of gas hydrate in the north slope of South China Sea should be further investigated.