水合物脊ODP1247站位天然气水合物藏的甲烷来源和成藏过程模拟

海洋天然气水合物体系天然气水合物成藏受甲烷供给及埋藏的控制.根据海洋天然气水合物体系甲烷的质量守恒,建立了海洋环境沉积物孔隙水溶解甲烷对流和扩散作用及微生物原位产甲烷作用供给甲烷形成天然气水合物的数值模型,对水合物脊ODP1247站位天然气水合物成藏过程进行了模拟研究,结果表明该站位孔隙水溶解甲烷的对流和扩散作用是天然气水合物成藏过程中最主要的甲烷供给方式,微生物原位生成甲烷供给的比例很小,并且在1.67 Ma以来天然气水合物藏受沉积速率变化而动态变化,但幅度不大,至今形成的水合物饱和度约0~3%,与钻探确定的饱和度接近.

Prediction of the methane supply and formation process of gas hydrate reservoir at ODP 1247, Hydrate Ridge

The formation of gas hydrate reservoir in marine sediments is mainly controlled by methane supply and sedimentary burial. Based on mass balance in marine gas hydrate system, a numerical prediction model of gas hydrate formation was established considering the methane supplied by dissolved methane diffusion and porewater advection and in-situ methanogenes. A case study of ODP sites 1247 shows that dissolved methane transported by molecular diffusion and porewater advection is the major supply of methane for gas hydrate formation, while in-situ methanogenesis contributes little to the gas hydrate reservoir. The gas hydrate reservoir was slightly changed by the variation of sedimentary rate since 1.67 Ma B.P. The model-derived hydrate saturation is ~0~3% up to date, which is consistent with that determined through ODP drilling.