Abstract: Methane hydrates formed in porous media with different sizes were experimented in laboratory.The concentrations of main ions in pore water before and after experiments were determined.It was found that the ionic concentrations in pore water showed obviously anomalous during gas hydrate formation in porous media.The salt-removing effect during formation of gas hydrate was dominated by methane consumption.More gas consumption resulted in a large amount of gas hydrate and stronger salt-removing effect.However,variations of concentrations for different ions were different in the pore water.The high-frequency vibration could accelerate reaction greatly.The coarse sediments with grain diameters over 125μm had little influence on formation speed of methane hydrates,whereas the fine sediments with grain diameters bellow 74μm obviously obstructed formation of methane hydrates.The influence of pressure on salt-removing effect indicated that the reaction time and the subcooling temperature submitted a relationship of power function under the same conditions.

Key words: porous media, methane hydrates, ionic concentration, salt-removing effect, geochemical characteristic

摘要： 利用不同粒径的多孔介质模拟了海洋天然气水合物的生成过程,测定了孔隙水中主要离子质量浓度的变化.研究结果表明,甲烷水合物的生成过程使周围沉积物孔隙水中离子质量浓度发生异常.水合物生成引起的排盐效应主要取决于耗气量.耗气量越大,生成水合物的量越大,排盐效应也就越强,但孔隙水溶液中不同离子质量浓度的变化并不一致.高频振动大大加快了反应速度;粗颗粒(粒径大于125μm)沉积物对水合物生成速度影响不大,而细颗粒(粒径小于74μm)沉积物则明显阻碍水合物的生成.压力对排盐效应的影响体现在反应时间上.在相同反应条件下,反应时间与过冷温度呈幂函数关系.

关键词: 多孔介质, 甲烷水合物, 离子质量浓度, 排盐效应, 地球化学特征