To better understand and implement the CO₂ sequestration project, it is of significance to investigate the interaction of shales with CO₂ and its potential effects on the pore morphology. In this study, two marine shale samples and two terrestrial shale samples were prepared and treated with subcritical CO₂ (30 $℃$ and 5 MPa) and supercritical CO₂ (80 $℃$ and 20 MPa) in a geochemical reactor. Various methods, including low-pressure carbon dioxide adsorption (LP-CO₂A), low-pressure nitrogen adsorption (LP-N₂A), high-pressure mercury intrusion porosimetry (HP-MIP) and fractal theory, were used to gain insights into the changes in the shale pore structure after 14 days of CO₂ saturation. According to the results, the phase states of CO₂ obviously affected the variations of pore structure parameters during the physical and chemical reactions in shales. Interactions of supercritical CO₂ with shales created a more obvious effect on the pore structure compared to those of subcritical CO₂, which was attributed to the greater dissolution and expansion effect as well as the extraction mechanism associated with supercritical CO₂. After exposing the shale samples to subcritical CO₂, the pore size distributions (PSDs) of the treated shale samples were lower than those of the raw samples at all diameter scales, indicating that the number of pores decreased due to the reactions. Furthermore, it was found that after supercritical CO₂ treatment, the micropore and mesopore structure parameters of the marine shale samples obviously decreased with an increase in macropore structure parameters, leading to the reduction in fractal dimensions in smaller pores, while the terrestrial shale samples appeared to represent a contrary trend. These findings will provide experimental evidence for further assessment of the mechanisms for CO₂ geological sequestration with enhanced shale gas recovery.

为了更好地理解和实施CO ₂隔离项目，研究页岩与CO ₂的相互作用及其对孔隙形态的潜在影响具有重要意义。在这项研究中，准备了两个海相页岩样品和两个陆相页岩样品，并用亚临界CO ₂（30$℃$和5 MPa）和超临界CO ₂（80$℃$和20兆帕的压力）。利用低压二氧化碳吸附法（LP-CO ₂ A），低压氮气吸附法（LP-N ₂ A），高压汞侵入孔隙率法（HP-MIP）和分形理论等各种方法来获得对CO ₂饱和14天后页岩孔隙结构变化的见解。根据结果​​，CO ₂的相态明显影响页岩理化反应过程中孔隙结构参数的变化。与亚临界CO ₂相比，超临界CO ₂与页岩的相互作用对孔隙结构的影响更为明显。这归因于更大的溶解和膨胀作用，以及与超临界CO ₂有关的萃取机理。在页岩样品暴露于亚临界CO _2后，在所有直径范围内，处理过的页岩样品的孔径分布（PSDs）均低于原始样品的孔径分布（PSDs），表明孔的数量由于反应而减少。此外，发现在超临界CO _2之后处理后，海相页岩样品的微孔和中孔结构参数随着大孔结构参数的增加而明显降低，导致较小孔隙中的分形维数减小，而陆相页岩样品似乎代表相反的趋势。这些发现将为进一步评估页岩气采收率提高CO ₂地质封存机理提供实验依据。