Gas injection for enhancing gas recovery (GI–EGR) is a multifaceted process that requires a solid theoretical foundation to be implemented orderly. However, there are limited reports on the micro-mechanisms of GI–EGR technology applied to coalbed methane reservoirs, especially for deep strata. To address this gap, this study utilized molecular simulation techniques to construct the organic pore models of anthracite with varying sizes and morphologies, and explored the micro-dynamic behaviors of CH₄ and various gas injected components including N₂, CO₂ and flue gas confined in nanopores. The aim was to reveal the competitive adsorption mechanisms of gases in multi-component systems under shallow and deep geological conditions. The results demonstrated that the isosteric heats of CH₄, N₂ and CO₂ all increased after the transition from shallow to deep, with rising amplitudes of 18.8%, 22.8% and 17.8%, respectively, in the respective single-component systems. In multi-component adsorption models, the isosteric heats remained higher than those under shallow conditions, but there were some small fluctuations due to the interference between various gases. On the other hand, the self-diffusion coefficients of single CH₄, N₂ and CO₂ in the deep condition decreased by 37.6%, 27.2% and 23.1%, respectively, compared to those in conventional shallow conditions. As a consequence, the difference in diffusivity among various gases would get narrowed. The molecular-level observations herein have the potential to improve the understanding of gas occurrence and lay a solid foundation for the GI–EGR technology.

摘要

注气提高气体回收率（GI-EGR）是一个多方面的过程，需要坚实的理论基础才能有序实施。然而，关于GI-EGR技术应用于煤层气藏，特别是深层地层的微观机制的报道还很有限。_{为了解决这一问题，本研究利用分子模拟技术构建了不同尺寸和形态的无烟煤有机孔隙模型，并探讨了CH 4}和各种气体注入组分（包括N ₂、CO ₂和烟气约束）的微观动力学行为。在纳米孔中。目的是揭示浅层和深层地质条件下多组分系统中气体的竞争吸附机制。结果表明，从浅层到深层，CH ₄、N ₂和CO ₂的等量热均有所增加，在各自的单组分体系中，上升幅度分别为18.8%、22.8%和17.8%。在多组分吸附模型中，等量热仍然高于浅层条件下的等量热，但由于各种气体之间的干扰而存在一些小波动。另一方面，与常规浅层条件相比，深部条件下单一CH ₄、N ₂和CO _{2的自扩散系数分别降低了37.6%、27.2%和23.1%。}结果，各种气体之间的扩散率差异将会缩小。本文的分子水平观察有可能提高对气体发生的理解，并为 GI-EGR 技术奠定坚实的基础。