Abstract Sand production, which poses a great challenge for sustainable methane gas production, is commonly encountered during natural gas extraction from unconsolidated hydrate-bearing sediments. However, studies on the subject are still limited. This paper provides a numerical model, coupled with thermo-hydro-mechanical (THM) processes, which is capable to characterize the process of sand production in gas hydrate-bearing sediments. The numerical simulator is developed by introducing the newly developed particle migration module into the existing framework of the THM coupled simulator HydrateBiot. The dynamic of sand production was investigated numerically, and the influence of various parameters on sand, gas and water production was studied. The simulation results show that particle detachment and migration mainly occurs in the vicinity of wellbore, while lowering the depressurization rate can mitigate sand production to some extent without significantly inhibiting the gas production. The using of the sand control device can effectively inhibit sand production, but its blockage will cause a significant drop in gas productivity. Sensitivity analyses of the critical fluidization velocity and solid-liquid velocity show that the increase of solid particle concentration will significantly affect the fluidity of water, thus affecting the depressurization process and gas productivity. It is also found that the massive particle detachment and migration may cause the appearance of clogging area in the vicinity of the wellbore and severely restrict the sustainable gas production. The numerical model and analysis presented here could provide useful insight into sand detachment, migration and production processes induced by methane gas production using depressurization method in the hydrate-bearing marine sediments.

中文翻译：

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松散含水合物沉积物采气过程出砂数值分析

摘要 出砂对可持续的甲烷气生产提出了巨大的挑战，在从松散的含水合物沉积物中提取天然气过程中经常遇到。然而，关于该主题的研究仍然有限。本文提供了一个数值模型，结合热-水-机械 (THM) 过程，能够表征含天然气水合物沉积物中的出砂过程。数值模拟器是通过将新开发的粒子迁移模块引入到THM耦合模拟器HydrateBiot的现有框架中而开发的。数值研究了出砂动态，研究了各种参数对出砂、产气和产水的影响。模拟结果表明，颗粒脱离和运移主要发生在井筒附近，而降低降压速度可以在一定程度上缓解出砂，而不会明显抑制产气。使用防砂装置可以有效抑制出砂，但其堵塞会导致产气率显着下降。临界流化速度和固液速度的敏感性分析表明，固体颗粒浓度的增加会显着影响水的流动性，从而影响降压过程和产气率。还发现大量颗粒脱离和迁移可能导致井筒附近出现堵塞区，严重制约天然气的可持续生产。