The geomechanical behaviour of hydrate-bearing sediments during methane gas production is complex due to the spatial and temporal changes in stress, pore pressure, temperature, and phase change. In order to evaluate the geomechanical risks during methane gas production, it is necessary to understand the thermo-hydro-mechanical (THM) responses in the production region that recovers methane gas from the hydrate-bearing sediments. In this study, a fully coupled THM numerical simulator code was used to examine the reservoir scale field behaviour observed during the gas production trial conducted at the Eastern Nankai Trough, Japan in March, 2013. Using the available field investigation data, history matching of the gas production test was conducted to evaluate the methane gas production process. The fully coupled model allowed examination of the mechanical response using the critical state based constitutive model proposed by Uchida et al. (2012). The model parameters were determined from the results of triaxial compression tests conducted on recovered core samples. Based on the reservoir scale simulation results, this paper investigated the mechanical responses of five selected elements at different locations in the hydrate gas production region. The mechanical responses of hydrate-bearing sediments at specific locations within the production region are related to their hydrate dissociation status, which typically can be divided into before, during and after stages of hydrate dissociation. The 260 days gas production simulation suggests an increase in effective stresses accompanied by shearing deformation, which makes the soil more plastic. Potential geomechanical risks (such as wellbore stability and formation compaction) associated with the observed changes in stress/strain were also identified.

由于应力，孔隙压力，温度和相变的时空变化，甲烷气体生产过程中含水合物沉积物的地质力学行为是复杂的。为了评估甲烷气生产过程中的地质力学风险，有必要了解生产区域中从含水合物沉积物中回收甲烷气的热-水-机械（THM）响应。在这项研究中，使用完全耦合的THM数值仿真器代码检查了在2013年3月在日本东部南海海槽进行的天然气生产试验中观察到的储层规模现场行为。进行了产气测试以评估甲烷气的生产过程。完全耦合模型允许使用Uchida等人提出的基于临界状态的本构模型检查机械响应。（2012）。根据对回收的岩心样品进行的三轴压缩测试的结果确定模型参数。基于储层规模模拟结果，本文研究了水合物气生产区中不同位置的五个选定元素的力学响应。在生产区域内特定位置的含水沉积物的机械响应与其水合物的解离状态有关，通常可以将其分为水合物解离阶段之前，期间和之后。260天的产气量模拟表明有效应力增加，并伴随剪切变形，使土壤更加可塑性。还确定了与观察到的应力/应变变化相关的潜在地质力学风险（例如井筒稳定性和地层压实）。