The replacement of gas hydrate in clayey sediment by a CO2/N2 (20:80) gas mixture injection was experimentally studied to explore the influence of clay on the gas exchange behaviours in the gas hydrate. Clay (montmorillonite) and silica sand were mixed in three different proportions (clay mass ratios of 10%, 30% and 50%) to simulate the host sediments of natural gas hydrate while pure silica sand sediment was selected for comparison. Experimental results showed that clay hindered gas diffusion during the initial replacement stage and thus reduced the methane recovery rate. In the later stage, the gas exchange between CO2/N2 and methane in the hydrate structure might be subject to thermodynamic inhibition and geometric constraints of the clay interlayer. Moreover, the CO2 sequestration ratio was lowered significantly in the sediment with a 50% clay mass ratio. Therefore, it was determined that clay has an inhibitory effect on gas hydrate replacement by CO2/N2.

中文翻译：

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含水合物粘土沉积物CO2/N2置换产甲烷实验研究

以CO2/N2 (20:80) 混合气注入替代粘土沉积物中的天然气水合物进行了实验研究，以探讨粘土对天然气水合物中气体交换行为的影响。粘土（蒙脱石）和硅砂以三种不同的比例（粘土质量比为10%、30%和50%）混合模拟天然气水合物的宿主沉积物，同时选择纯硅砂沉积物进行比较。实验结果表明，粘土在初始置换阶段阻碍了气体扩散，从而降低了甲烷回收率。后期，水合物结构中CO2/N2与甲烷之间的气体交换可能受到粘土夹层的热力学抑制和几何约束。而且，粘土质量比为 50% 的沉积物中 CO2 封存率显着降低。因此，确定粘土对CO2/N2 置换天然气水合物具有抑制作用。