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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。
A comprehensive survey has revealed a series of geological, geophysical and geochemical indicators that show the presence of gas hydrates on the northern slope of the South China Sea. The results show that two types of gas hydrate systems, low flux diffusive hydrate and high flux seepage hydrate, coexist in the northern slope of South China Sea, especially in the Dongsha and Shenhu waters. Information obtained on gas hydrate drilling voyages provides a basis for further understanding of natural gas hydrate systems in Shenhu and Dongsha areas. Drilling results demonstrate that strong sub-seafloor reflections are often associated with low-saturation gas hydrate-bearing sediments; highly saturated gas hydrates generally do not need to correspond to seafloor reflections identified on seismic profiles and are not associated with gas seepage And the fault structure and other related features. Geochemical data show that the gas source of natural gas hydrate in Shenhu sea area and Dongsha sea area is mainly microbial genesis gas. The natural gas hydrate distribution area confirmed by Shenhu sea area drilling has 16 billion cubic meters of methane geological reserves. With the current natural gas hydrate mining technology and process conditions, mining has great difficulties and needs to be developed with more advanced technologies. The logging-while-drilling data show that there exists moderate-high saturation hydrate in the shallow part of the Dongsha Sea and low saturation gas hydrate above the bottom boundary of the deep hydrate stability zone. The continental slope gas hydrate in the northern part of the South China Sea needs to be further explored for its occurrence status, saturation, reservoir characteristics and resource prospects.