Abstract Dynamic evolution of coal deformation and permeability, induced by changes in in situ stresses with continued depletion in coalbed methane (CBM) reservoirs, has been extensively investigated both experimentally and theoretically. However, the impact of stress-/strain-controlled mechanics on permeability variation is somewhat unclear. To examine this behavior, gas flow experiments were conducted under best replicated in situ conditions. Considering that coal anisotropy may lead to changes in deviator stress and coal failure behavior during primary depletion, core flooding experiments were carried out to investigate the anisotropic behavior of coal. Using the experimental results, Mohr's circle of strain was first employed to facilitate the process of analyzing the dynamic deformation behavior of coal. Next, a strain-based failure criterion was developed to analyze the failure tendency of CBM reservoirs in order to explain the sudden increase in permeability observed during experimental work. The results show that the abrupt increase in permeability can be attributed to shear failure of coal due to increased deviator stress resulting from in situ stress redistribution after significant depletion. This study sheds light on the influence of stress relaxation on coal deformation behavior, failure tendency and permeability evolution, with practical implication for gas flow modeling of CBM reservoirs.

中文翻译：

---

原位应力松弛对煤层气储层原生枯竭变形行为及渗透率变化的实验研究

摘要 随着煤层气（CBM）储层中地应力的变化，煤层变形和渗透率的动态演化已经在实验和理论上得到广泛研究。然而，应力/应变控制力学对渗透率变化的影响尚不清楚。为了检查这种行为，在最佳复制的原位条件下进行了气流实验。考虑到煤的各向异性可能导致一次衰竭过程中偏应力和煤破坏行为的变化，开展了岩心驱替实验，研究了煤的各向异性行为。使用实验结果，首先采用莫尔应变圆来促进分析煤的动态变形行为的过程。下一个，开发了一种基于应变的破坏准则来分析煤层气储层的破坏趋势，以解释实验工作期间观察到的渗透率突然增加。结果表明，渗透率的突然增加可归因于煤的剪切破坏，这是由于显着枯竭后地应力重新分布导致偏应力增加所致。该研究揭示了应力松弛对煤变形行为、破坏趋势和渗透率演化的影响，对煤层气储层的气流建模具有实际意义。结果表明，渗透率的突然增加可归因于煤的剪切破坏，这是由于显着枯竭后地应力重新分布导致偏应力增加所致。该研究揭示了应力松弛对煤变形行为、破坏趋势和渗透率演化的影响，对煤层气储层的气流建模具有实际意义。结果表明，渗透率的突然增加可归因于煤的剪切破坏，这是由于显着枯竭后地应力重新分布导致偏应力增加所致。该研究揭示了应力松弛对煤变形行为、破坏趋势和渗透率演化的影响，对煤层气储层的气流建模具有实际意义。