Dynamic behavior of hydrate dissociation for gas production via depressurization and its influencing factors
Dynamic behavior of hydrate dissociation for gas production via depressurization and its influencing factors
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DOI：
10.1016/j.petrol.2016.07.014
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发表时间：
2016-10
影响因子：
--
通讯作者：
Dexiang Li;S. Ren;Liang Zhang;YiXi Liu
中科院分区：
文献类型：
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作者：
Dexiang Li;S. Ren;Liang Zhang;YiXi Liu
天然气水合物是一种极具开发潜力的能源。通过降压生产天然气是可行的，这已被应用于从Messoyakha的天然气水合物矿床中提取天然气。了解水合物分解的动力学行为，即降压过程中压力、温度和产气率的变化，对于水合物分解过程的优化和地质灾害的预测具有重要意义。利用自行设计的实验装置，在模拟多孔介质中进行了不同条件下甲烷水合物的生成和分解实验。模拟了不同水合物饱和度条件下充填砂中水合物的形成过程，分析了水合物分解过程的动力学行为及其影响因素，并以产气速率、累积产气量以及产气过程中伴随的温度和压力变化为例进行了说明。实验结果表明，生产压力较低时，可在早期抑制水合物的分解，使分解区局部温度降低，使水合物重新稳定;逐步降低生产压力可提高采气效率。填砂层的高渗透率有利于提高产气量，但也会导致温度和压力的快速下降。在水合物饱和度较高的情况下，水合物分解的时间变得更长，并且可能需要降压沿着其他刺激方法，例如热刺激，以有效地生产气体。
Natural gas hydrate can be a potential energy resource to be developed in the near future. Gas production is feasible via depressurization, which has been applied for gas extraction from gas hydrate deposits in Messoyakha. Understanding the dynamic behavior of hydrate dissociation, i.e. the variations of pressure, temperature and gas production rate during the depressurization process, is important for process optimization and predications of geological hazards caused by hydrate dissociation. In this study, methane hydrate formation and dissociation experiments were conducted using a self-designed apparatus under different conditions in simulated porous media. Hydrate formation in sand packs with different hydrate saturations were simulated, and the dynamic behavior of hydrate dissociation process and its influencing factors were analyzed, illustrated by gas production rate, accumulated gas production, and the associated temperature and pressure changes in the gas production process. The experimental results show that hydrate dissociation can be inhibited in the early stage if the production pressure is low, which can cause a decrease of the local temperature in the dissociation zone and restabilize the hydrate, and the efficiency of gas production can be improved by reducing the production pressure gradually. High permeability of the sand packs is conductive to increase gas production rate, but it can also induce a fast decrease on temperature and pressure. The time for hydrate dissociation becomes longer in the case of a higher hydrate saturation, and depressurization along with other stimulation methods, such as thermal stimulation, may be required for efficient gas production.