In this study, the adsorption–desorption/induced strains/permeability characteristics of seven columnar coal samples with R_o.ran ranging from 0.42 to 3.23% were monitored dynamically during N₂-enhanced coalbed methane (N₂–ECBM) recovery. The results showed that N₂ injection and sealing (N₂–IS) is an important step in N₂–ECBM recovery, with average desorption of 60.25%. During desorption with stepwise depressurization (DSD), the desorption volume increased linearly with time. The breakthrough point of gas production was in the first gas drainage phase, and the low-rank coal reservoirs entered the depletion well stage earlier. The samples were subjected to N₂–IS and DSD, the cumulative desorption of the samples was in the 88.03–100.96% range, and the average desorption of the medium-rank coals was 100.40%. The residual volume strain was negative in medium-rank coals and caused by pore–fracture structural damage. The induced strain behavior was independent of gas composition, but with the gas volume being polynomial, it had a predictive effect. The permeability recovery percentage (PRP) during N₂–IS was in the order of medium- > high- > low-rank coal, and the PRP of medium-rank coal was up to 90%. The strain sensitivity coefficient of low-rank coal increased with increase in volume strain, that of medium-rank was independent of volume strain, and that of high-rank coal decreased with increase in volume strain. This work revealed that, by injecting N₂ into the reservoir and sealing the well for a certain period of time while maintaining high reservoir pressure, CH₄ desorption induced coal volume shrinkage, the fracture aperture was restored, and some new fractures were induced, increasing permeability; in addition, DSD can be more consistent with the gas production process.

在本研究中，在 N ₂增强煤层气 (N ₂ -ECBM) 回收过程中动态监测了 7 个R _o.ran范围为 0.42% 至 3.23% 的柱状煤样品的吸附-解吸/诱导应变/渗透特性。结果表明，N ₂注入和密封（N ₂ -IS）是N ₂ -ECBM 回收的重要步骤，平均解吸率为60.25%。在逐步减压 (DSD) 解吸过程中，解吸体积随时间线性增加。采气突破点在第一抽采阶段，低阶煤储层较早进入枯竭井阶段。样品经受 N ₂–IS和DSD，样品的累积解吸在88.03-100.96%范围内，中煤的平均解吸为100.40%。中阶煤的残余体积应变为负值，是由孔隙-裂缝结构破坏引起的。诱导应变行为与气体成分无关，但由于气体体积为多项式，因此具有预测效果。N ₂ -IS过程中渗透率恢复百分比（PRP）的顺序为中-> 高-> 低阶煤，PRP中煤品位高达90%。低阶煤的应变敏感性系数随着体积应变的增加而增加，中阶煤的应变敏感性系数与体积应变无关，高阶煤的应变敏感性系数随着体积应变的增加而降低。本研究表明，通过向储层注入 N ₂并封井一定时间，同时保持较高的储层压力，CH ₄解吸引起煤体积收缩，裂缝孔径得到恢复，并产生一些新的裂缝，增加渗透性；此外，DSD 可以更符合产气过程。