深部煤层气产出与浅部存在较大差异，维持储层渗透性或尽可能减小渗透率损失、提高煤层气(CH₄)解吸效率及准确预测扩散规律是深部煤层气产出面临的重要挑战，亟需通过技术创新和理论研究攻关突破。

对国内外煤储层渗透性、煤层气解吸、扩散等基础研究进展进行系统分析，结合深部煤储层排采阶段划分和不同阶段煤层气运移主要形式，总结深部煤层气产出机制及其影响因素。

结果表明：(1) 深部煤层气产出划分为快速上产、相对稳产、缓慢递减和低产4个阶段。(2) 快速上产和相对稳产阶段，储层压力高，气源以游离气为主，甲烷运移以渗流为主导，其主要影响因素包括煤体结构、孔裂隙发育程度、储层温度、原位地应力、有效应力等。该阶段应尽可能地减少渗透率损失，避免直接压开碎粒煤、糜棱煤占比较大的储层；相对稳产阶段之后储层温度的增渗作用会随着滑脱效应的增强逐渐增大；控压降、慢排采有助于减缓储层渗透率衰减。尽管在低产气阶段原生裂隙及人工裂隙渗透率损失率均接近100%，但不可逆渗透率损失率却远远低于浅部煤储层，昭示着储层二次改造增产的可行性。(3) 快速上产至相对稳产阶段，吸附气开始缓慢解吸，扩大解吸范围、保证渗流通道，提高煤层气井产量是重中之重。深部煤储层中吸附气解吸较浅部所需时间长，临界解吸压力难以准确判断，解吸气体运移通道易压缩闭合，解吸范围受限。实验研究时应选用逐级降压解吸方式，可精准预估煤层气开采率；排采过程控制储层压力缓慢降低，可有效提升微孔中吸附气的解吸率。(4) 低产气阶段，产气以远井区域解吸气供给为主，甲烷扩散决定煤层气井产量，扩散系数的准确测试和动态模型构建是关键。扩散系数各向异性特征显著，目前CH₄扩散模型对煤体结构的各向异性特征很少涉及；构建CH₄时变扩散模型，需考虑煤体多尺度孔隙−显微裂隙中扩散模式；结合煤中多尺度孔裂隙精细表征实验与高温高压核磁成像分析技术，可表征不同孔径间CH₄密度变化。本次系统的总结和认识，将理论与生产实践相结合，进一步完善深部煤层气开发理论基础。

The production characteristics of coalbed methane (CBM) from deep reservoirs differ significantly from those of CBM from shallow reservoirs. Key challenges in deep CBM production include maintaining reservoir permeability or minimizing permeability loss, enhancing CBM (CH₄) desorption efficiency, and accurately predicting the laws of CH₄ diffusion. There is an urgent need to overcome these challenges through technological innovation and theoretical research.

This study systematically analyzed the advances in domestic and international research on coal reservoir permeability, CBM desorption, and CBM diffusion. By integrating the classification of production stages of deep coal reservoirs with the dominant CBM migration mechanisms of varying stages, this study summarized the mechanisms and influential factors of deep CBM production.

The results indicate that deep CBM production can be divided into four stages: rapid production increase, relatively stable production, gradual production decrease, and low production. During the former two stages, reservoir pressure remains high, free gas serves as a primary gas source, and methane migration is dominated by seepage flow. Key influential factors of both stages include coal structure, developmental degrees of pores and fractures, reservoir temperature, in situ stress, and effective stress. At these stages, minimizing permeability loss is crucial, and direct fracturing should be avoided in reservoirs with a high proportion of granulated and mylonite coals. After the relatively stable production phase, an increase in the reservoir permeability caused by reservoir temperature will gradually increase with an enhancement in the slip effect. Controlling pressure drop and slow production can help to slow down the decline of reservoir permeability. In the low-production stage, the permeability loss rate caused by both primary and artificially induced fractures approaches 100%. However, the irreversible permeability loss rate remains significantly lower than that of shallow coal reservoirs, suggesting the feasibility of secondary reservoir stimulation for increased production. From the rapid production increase stage to the relatively stable production stage, the adsorbed gas begins to undergo gradual desorption. In this case, the primary objectives are to expand the desorption range, ensure the opening of seepage channels, and enhance the productivity of CBM wells. Compared to shallow reservoirs, the desorption of adsorbed gas in deep coal reservoirs occurs over a prolonged period, with the critical desorption pressure being challenging to determine accurately. Furthermore, the pathways for gas migration are prone to be compressed and close, leading to a limited desorption range. To achieve precise estimations of CBM recovery rates, it is necessary to adopt a stepwise depressurization desorption method in experimental research. Specifically, achieving a gradual decrease in the reservoir pressure using control measures during CBM production can effectively enhance the desorption rate of adsorbed gas in micropores. In the low-production stage, gas production primarily originates from desorbed gas in remote well areas. In this stage, the production of CBM wells is determined by methane diffusion, with the accurate measurement of the diffusion coefficient and the development of dynamic diffusion models playing a crucial role. Notably, the diffusion coefficient exhibits significant anisotropy, yet current CH₄ diffusion models seldom account for the anisotropic characteristics of coal structure. It is necessary to develop a time-varying CH₄ diffusion model while considering the CH₄ diffusion patterns across multi-scale pores and microfractures in coals. Experiments on the fine-scale characterization of multi-scale pores and fractures, combined with high-temperature with high-pressure nuclear magnetic resonance imaging, allow for the characterization of variations in CH₄ density across different pore sizes. This systematic review integrates theories and practice, further laying a theoretical foundation for deep CBM recovery.