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海底冷泉活动区不仅有天然气向海底的渗漏,同时还存在孔隙水的对流,并可能改变天然气水合物体系的温度和盐度,进而影响天然气水合物的成藏.利用建立的天然气水合物生成动力学模型和水合物脊南部高地实测的温度和盐度等条件,模拟了三种典型流体活动区(生物蛤区、细菌席区和冒气区)不同的流体通量条件下天然气水合物的成藏过程.其中生物蛤区孔隙水通量<20kgm-2a-1,模拟表明孔隙水对流作用对体系的温度和盐度无影响或影响很小,由于天然气水合物生成作用,体系盐度升高显著(最高>0.8mol kg-1),温度发生一定的升高,天然气水合物稳定带底界逐步升高到约70mbsf,水合物饱和度高.细菌席区孔隙水通量100～2500kg m-2a-1,孔隙水对流作用抑制了盐度升高,同时使体系温度升高显著,模拟的盐度为海水值或略高于海水值(<0.65mol kg-1),同时天然气水合物稳定带底界显著上升到浅层50mbsf以上,甚至可达浅层3mbsf,天然气水合物饱和度较低.而在冒气区,孔隙水通量可达1010kg m-2a-1,经历9min渗漏,通道温度达到流体源区值,通道内无天然气水合物生成.因而,模拟结果表明孔隙水通量越高,孔隙水盐度越低,温度上升越显著,天然气水合物稳定带底界上移越显著,单位面积天然气水合物生成速率也越低,天然气水合物饱和度越小,天然气水合物资源量越小.
The seabed cold spring activity zone not only has the natural gas leakage to the seafloor, but also the pore water convection, and may change the temperature and salinity of the gas hydrate system, thus affecting the gas hydrate accumulation. Using the established gas hydrate formation Kinetic model and the temperature and salinity measured in the southern highlands of the hydrate ridges, simulated the effects of different gas fluxes on the gas hydrate of the three typical fluid activity zones (bio-clam zone, bacterial zone and aeration zone) The pore water flux in biological clam zone is less than 20kgm-2a-1. The simulation shows that the convection of pore water has no or little effect on the temperature and salinity of the system. Because of the formation of gas hydrate, (Up to> 0.8mol kg-1), the temperature increased to a certain extent, and the bottom boundary of gas hydrate stability gradually increased to about 70mbsf, the hydrate saturation was high.The pore water flux of bacteria was 100 ~ 2500kg m -2a-1. The convection of pore water suppressed the salinity increase and the temperature of the system increased significantly. The simulated salinity was slightly higher than seawater (<0.65mol kg-1), and the natural gas hydrate Stable bottom line significantly Up to shallow 50mbsf, even up to shallow 3mbsf, natural gas hydrate saturation is low, while in the rised area, pore water flux up to 1010kgm-2a-1, after 9min leakage, the channel temperature reaches the fluid Source zone value and no formation of gas hydrate in the channel.Therefore, the simulation results show that the higher the pore water flux, the lower the pore water salinity, the more significant the temperature rise, the more the gas hydrate stable bottom zone moves up significantly, and the unit area Natural gas hydrate formation rate is also lower, the smaller the natural gas hydrate saturation, the smaller the amount of natural gas hydrate resources.