Abstract This study presents a coupled dual porosity thermal-hydraulic-mechanical (THM) model of non-isothermal gas flow during CO2 sequestration in coal seams. Thermal behaviour is part of the disturbed physical and chemical condition of a coal seam caused by CO2 injection, and must be understood for accurate prediction of CO2 flow and storage. A new porosity-permeability model is included for consideration of the fracture-matrix compartment interaction. The new model is verified against an analytical solution and validated against experimental measurements, before being used to analyse coupled THM effects during CO2 sequestration in coal. A simulation of CO2 injection at a fixed rate shows the development of a cooling region within the coal seam due to the Joule-Thomson effect, with the temperature in the vicinity of the well declining sharply before recovering slowly. The temperature disturbance further from the well is more gradual by comparison. Under the simulation conditions studied, CO2 injection increases coal matrix porosity and decreases the porosity and permeability of the natural fracture network, especially in the vicinity of the injection well, due to adsorption-induced coal swelling. Compared with the effects of gas pressure and temperature, the matrix-fracture compartment interaction plays an important role in changes of porosity and permeability. Considering the temperature disturbance caused by CO2 injection under the set of representative conditions studied, the coupled model can provide an insight into the associated effects on CO2 flow and storage during its sequestration in coal seams.

中文翻译：

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煤中CO2封存过程中双孔隙度耦合热-水-力学行为的数值分析

摘要 本研究提出了煤层中 CO2 封存期间非等温气流的双孔隙度热-水力-机械 (THM) 耦合模型。热行为是由 CO2 注入引起的煤层物理和化学条件紊乱的一部分，必须了解热行为才能准确预测 CO2 流动和储存。包括一个新的孔隙度-渗透率模型以考虑裂缝-基质隔间相互作用。在用于分析煤中 CO2 封存期间的耦合 THM 效应之前，新模型已根据解析解进行验证并根据实验测量进行验证。以固定速率注入 CO2 的模拟表明，由于焦耳-汤姆逊效应，煤层内形成了一个冷却区域，井附近的温度急剧下降，然后缓慢恢复。相比之下，离井更远的温度扰动更加平缓。在所研究的模拟条件下，由于吸附引起的煤膨胀，CO2 注入增加了煤基质的孔隙度并降低了天然裂缝网络的孔隙度和渗透率，尤其是在注入井附近。与气压和温度的影响相比，基质-裂缝隔室相互作用对孔隙度和渗透率的变化起着重要作用。考虑到在所研究的一组代表性条件下由 CO2 注入引起的温度扰动，耦合模型可以深入了解 CO2 在煤层封存期间对 CO2 流动和储存的相关影响。