ORIGIN AND GENETIC MODEL OF POTENTIAL GAS HYDRATES IN XISHA TROUGH,SOUTH CHINA SEA
ORIGIN AND GENETIC MODEL OF POTENTIAL GAS HYDRATES IN XISHA TROUGH,SOUTH CHINA SEA
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发表时间：
2005
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通讯作者：
Wang Hong-yu;Su Chunyan;Zhang Hong-bo;Niu Binhua
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作者：
Wang Hong-yu;Su Chunyan;Zhang Hong-bo;Niu Binhua
西沙海槽地区具有良好的热成因气源、构造通道和深部压力运移条件，海底表层沉积物中甲烷气的成因可以指示潜在天然气水合物的成因，通过甲烷碳同位素测试和气态烃参数计算，发现西沙海槽海底表层沉积物中甲烷气主要来源于深部热成因气，运移成藏条件分析表明，甲烷气运移是断层渗滤和自由扩散分异相结合的综合方式，甲烷气有3种气源：①深部断层通道气态烃直接释放的气; ②动态变化的水合物分解产物，在渗流作用下或沿沿着向上运移; ③浅层生物气，不同地区的气源不同，甲烷气高值区与BSR区不完全一致，而与深部大断裂有关，甲烷气体的运移聚集方式间接表明西沙海槽潜在的天然气水合物是热成因的，其成因模式是断层-渗流综合地质模式。
Xisha Trough region has favorable thermogenic gas source,structural path,and deep pressure migration conditions.The origin of methane gas contained in the seafloor superficial sediment can indicate the genesis of potential gas hydrate.Through methane carbon isotope testing and gaseous hydrocarbon parameter calculation,we found that the methane gas contained in seafloor superficial sediment of Xisha Trough mainly came from deep thermogenic gas,and small quantity of gas from biogenic methane gas.The analysis of migration and accumulation conditions indicates that methane gas migration is a comprehensive fashion composed of fault filtration and free diffusion differentiation,and there are three methane gas sources:①gas that directly releases from gaseous hydrocarbon in the deep fault path;②gas that comes from dynamically changeable hydrate decomposition and migrates upward under the action of filtration or along a small and shallow fault;③biogenic gas in the shallow layers.Different regions have different gas sources,so regions of high values of methane gas are not completely consistent with BSR region,but correlative to deep large faults.Origin,migration and accumulation fashion of methane gas indirectly indicate that potential gas hydrate in Xisha Trough is thermogenic,and genetic model is comprehensive fault-filtration geologic model.