【摘要】 大规模高效CO₂地质封存是短期内快速实现CO₂减排的关键途径之一，以吸附特征为主要封存机制的深部不可采煤层CO₂封存具有规模化实施的潜力。为研究深部煤层CO₂封存机制，以沁水盆地无烟煤为研究对象，开展了高温高压CO₂吸附实验，并采用简化局部密度模型（SLD-PR）拟合，分析了温压变化下不同孔隙的吸附相密度分布特征，揭示了以吸附相密度和最大吸附层厚度协同变化为核心的煤层CO₂封存机理，最后通过准确划分孔内吸附空间与自由空间，预测了不同埋深下煤层CO₂封存量。研究结果表明：（1）不同温度下超临界CO₂吸附曲线均表现出典型的超临界气体吸附特征，过剩吸附量（最大值介于1·25～1·75 mmol/g）在达到最大值后下降；（2）孔隙内CO₂吸附层分为接触层、内层和过渡层，亚临界CO₂在孔内以单分子层吸附为主，而超临界CO₂吸附方式为多分子层吸附；（3）最大吸附层厚度随埋深增加而减小，与温度呈正相关，而与压力呈负相关；（4） CO₂平均吸附相密度随埋深“先增后减”，总封存量与绝对吸附量曲线在CO₂处于超临界状态下存在差异。结论认为：（1）在吸附空间与吸附相密度协变下，煤层CO₂微观封存模式随埋深可分为亚临界单分子层吸附、超临界类气态多分子层吸附型以及超临界类液态多分子层吸附3种类型，自由相封存量对总封存量的贡献随埋深增加，但吸附封存仍是煤层CO₂封存的主要方式；（2）研究成果揭示了原位煤层超临界CO₂封存机理，能够为深部煤层CO₂封存能力评价提供新认识。更多还原

【Abstract】 Large-scale efficient CO₂ geological storage is one of the key means to realize CO₂ emission reduction rapidly in a short term.CO₂ storage in deep unminable coal seams with adsorption as the main storage mechanism has the potential of large-scale implementation.In order to study the mechanisms of CO₂ storage in deep coal seams, this paper carries out a high-temperature and high-pressure CO₂ adsorption experiment on the anthracite coal taken from the Qinshui Basin. Then, the SLD-PR model is used for fitting, the adsorption density distribution characteristics of different pores with the variation of temperature and pressure are analyzed, and the CO₂ storage mechanisms in coal seams with the collaborative change of adsorbed phase density and maximum adsorption layer thickness as the core are revealed. Finally, the volumes of CO₂ storage in coal seams at different burial depths are predicted by classifying adsorption space and free space in pores accurately. And the following research results are obtained. First, the adsorption curves of supercritical CO₂ at different temperatures all present the typical adsorption characteristics of supercritical gas, with the excessive adsorption capacity（the maximum value ranging from 1.25 to 1.75 mmol/g） decreasing after reaching the maximum value. Second, the CO₂ adsorption layers in pores are divided into contact layers, inner layers and transition layers. In pores, subcritical CO₂ is mainly in the mode of monomolecular layer adsorption, while supercritical CO₂ is in the mode of multi-molecular layer adsorption. Third, the maximum adsorption layer thickness decreases with the increase of burial depth, and it is in positive correlation with temperature and negative correlation with pressure. Fourth,the average CO₂ adsorbed phase density increases firstly and then decreases with burial depth, and the total storage and the absolute adsorption curves are different when CO₂ is in the supercritical state. In conclusion, under the collaborative change of adsorption space and adsorbed phase density, the CO₂ microscopic storage models in coal seams can be classified into three types with the variation of burial depth, including subcritical monomolecular layer adsorption, supercritical gas-like multi-molecular layer adsorption, and supercritical liquid-like multi-molecular layer adsorption. What’s more, the contribution of free phase storage to the total storage increases with burial depth, but adsorption storage is still the main mode of CO₂ storage in coal seams. The research results reveal the storage mechanisms of supercritical CO₂ in in-situ coal seams, and can provide new understandings for the evaluation of CO₂ storage capacity in deep coal seams.更多还原