Optimization of the depressurization pathways plays a crucial role in avoiding potential geohazards while increasing hydrate production efficiency. In this study, methane hydrate was formed in a flexible plastic vessel and then gas production processes were conducted at constant confining pressure and constant confining temperature. The CMG-STARS simulator was applied to match the experimental gas production behavior and to derive the hydrate intrinsic dissociation constant. Secondly, fluid production behavior, pressure-temperature () responses, and hydrate saturation evolution behaviors under different depressurization pathways were analyzed. The results show that integrated gas-water ratio (IGWR) decreases linearly with the increase in depressurizing magnitude in each step, while it rises logarithmically with the increase in the number of steps. Under the same initial average hydrate saturation and the same total pressure-drop magnitude, a slow and multistage depressurization strategy would help to increase the IGWR and avoid severe temperature drop. The pore pressure rebounds logarithmically once the gas production is suspended, and would decrease to the regular level instantaneously once the shut-in operation is ended. We speculate that the shut-in operation could barely affect the IGWR and formation response in the long-term level.

中文翻译：

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使用缓慢的多级降压策略生产水合物的实验室研究

减压途径的优化在避免潜在的地质灾害同时提高水合物生产效率方面起着至关重要的作用。在这项研究中，甲烷水合物在柔性塑料容器中形成，然后在恒定的密闭压力和恒定的密闭温度下进行气体生产过程。使用CMG-STARS模拟器来匹配实验气体的生产行为并得出水合物的内在解​​离常数。其次，流体生产行为，压力-温度（）分析了不同减压途径下的水响应和水合物饱和演化行为。结果表明，每一步的总气水比（IGWR）随降压幅度的增加而线性下降，而随着步数的增加而对数增加。在相同的初始平均水合物饱和度和相同的总压降幅度下，缓慢而多阶段的降压策略将有助于增加IGWR并避免严重的温度下降。气体生产暂停后，孔隙压力将呈对数回弹状态，一旦关闭工作结束，孔隙压力将立即下降至正常水平。我们推测，从长远来看，闭井作业几乎不会影响IGWR和地层响应。