ScCO2-H2O作用下不同煤级煤化学结构变化的实验研究

超临界二氧化碳（ScCO₂）–H₂O–煤地球化学反应可造成煤物理结构和化学结构的改变，对煤层注CO₂增采甲烷的有效性尤为关键。为了探讨ScCO₂-H₂O-煤反应对不同变质程度煤化学结构的影响，选择3个不同煤化程度煤样，在自主研制的ScCO₂-H₂O-煤地球化学反应模拟实验装置中模拟1000m埋深条件下煤样与ScCO₂和去离子水反应240h，并对反应前后的煤样分别进行了X射线衍射和拉曼光谱实验，对比分析了反应前后煤样晶体结构和碳有序度的变化特征。测试结果表明:ScCO₂-H₂O反应破坏了煤的晶体完整性和碳有序度，改变了煤的大分子结构，且对低阶煤和中–高阶煤具有不同的影响，反应提高了低阶煤的平行定向程度，使其结构更加紧凑，减小了面网间距，而使中–高阶煤中无序单元增加，面网间距增大。该研究结果为CO₂-ECBM项目实施中ScCO₂-H₂O作用对煤储层吸附解吸特征和孔渗特征影响的研究奠定了微观尺度基础。 

Experiment study on the chemical structure changes of different rank coals under action of supercritical carbon dioxide and water

ScCO₂-H₂O-coal geochemical reaction can exert a great influence on the physical and chemical structure of coal, playing a critical role in the CO₂ injection and enhancing CH₄ recovery. To investigate the effects of ScCO₂-H₂O on chemical structure in coal, three coal samples of different metamorphic grades were exposed to supercritical CO₂ and deionized water under 1000m depth temperature and pressure conditions for 240h using a high pressure reactor(ScCO₂/H₂O simulation system and coal/rock geochemical reaction device). X-ray diffraction and Raman spectroscopy were used to provide change characteristics of crystal structure and carbon order degree of coal before and after the ScCO₂-H₂O treatment. The results show that the ScCO₂-H₂O reaction destroys the crystal structural integrity and carbon order degree and changes the macromolecular structure of coal, the effect mainly depends on the coal rank, i.e., for low rank coals, the degree of parallel orientation increases and makes its structure more compact, the lamellae spacing decreases; while for medium-high rank coals, the disordered structure and lamellae spacing of the coal microcrystalline structure increases. This study result has laid a micro-scale foundation for the adsorption/desorption, pore and permeability characterization of coal reservoir before and after ScCO₂-H₂O action in the implementation of the CO₂-ECBM project.