Natural gas in clathrate hydrates is regarded as a potential energy source that has received increased attention to optimize production strategies with controllable impacts on the environment. This paper investigates possible instability of a gently sloping reservoir of oceanic hydrates induced by gas production using the huff-puff method through a horizontal well. The geomechanical stability of the slope is analyzed within the framework of the limit equilibrium method by considering the dynamic change in the pore pressure and the strength parameters of the slope during gas production. The production process is simulated by a coupled analysis of heat and flow transport considering thermal effects of hydrate dissociation and formation, and the time-dependent pore pressure and strength parameters are attained from this analysis and passed to the slope stability analysis. Parametric studies are performed to screen the optimal production scenario under different site conditions. Being part of the huff-puff production process, thermal stimulation during the huff stage poses a risk of production-induced instability to the slope. Overpressure is the dominant cause for slope failure, and strength reduction due to hydrate dissociation plays a secondary role in the studied scenario. The production-induced slope failure likely takes place at a site with interbedded geological structures that promote overpressure expansion in a laterally extending band beneath the potential failure surface. Thus, the geological structures should be properly modelled in reservoir simulations, as they could impact the production effectiveness and geomechanical response of the reservoir remarkably. This study demonstrates a need for a multi-objective optimization procedure to seek the overall optimal production strategy, since the economically optimal option is not necessarily free of risk of production-induced geo-hazards.

笼形水合物中的天然气被认为是一种潜在的能源，已受到越来越多的关注，以优化对环境具有可控影响的生产策略。本文研究了使用霍夫-帕夫方法通过水平井，由产气引起的平缓倾斜的海洋水合物储层的不稳定性。在边坡极限平衡法的框架内，通过考虑孔隙压力的动态变化和产气过程中边坡的强度参数，对边坡的地质力学稳定性进行了分析。考虑到水合物解离和形成的热效应，通过热与流传输的耦合分析来模拟生产过程，通过该分析获得了随时间变化的孔隙压力和强度参数，并将其传递到边坡稳定性分析中。进行参数研究以筛选不同现场条件下的最佳生产方案。作为哈夫-帕夫生产过程的一部分，在哈夫-帕夫阶段的热刺激带来了生产引起的斜坡不稳定性的风险。过压是边坡破坏的主要原因，而水合物分解引起的强度降低在所研究的情况中起次要作用。由生产引起的边坡破坏很可能发生在具有相互交错的地质结构的地点，这些地质结构促进了潜在破坏面之下的横向延伸带中的超压膨胀。因此，应在储层模拟中对地质结构进行适当建模，因为它们会显着影响储层的生产效率和岩土力学响应。这项研究表明，需要一种多目标优化程序来寻求整体最优生产策略，因为经济上最优的选择不一定不一定要避免生产引起的地质灾害的风险。