Abstract With the increasing amount of CO2 in the atmosphere, geologic sequestration becomes a promising measure to reduce the rising concentration of CO2. During the process of CO2 injection into coal seam to store CO2, it is critical to select the appropriate coal seam. In order to study whether the intact or tectonic coal is more suitable for CO2 geological sequestration, the pore structure characteristics and fractal dimensions of these coal samples were analyzed by mercury intrusion porosimetry, N2 (77 K)/CO2 (273 K) adsorption methods, and methane adsorption and diffusion properties of these coal samples were obtained. The results show that tectonic coals have greater pore volume and specific surface area of micropore, mesopore and macropore, while the fractal dimensions of the tectonic coals are smaller (that is, simpler pore structure, smaller pore surface roughness) than that of the intact coals, indicating that tectonic coal has more favorable pore structure to provide more adsorption sites for CO2 storage. Furthermore, better connectivity as well as the adsorption and diffusion capacity of tectonic coals have been significantly improved compared to intact coals, which indicates that CO2 is easier to migrate into the internal pore system of tectonic coal in a short time, reducing the time consumed by CO2 injection into the coal seam, thus saving the cost of CO2 storage. Interestingly, a fractal conceptual model is proposed to account for the evolution of original long and complex pores were converted into short and simple pores, and closed pores transformed into connectivity pores during the formation of tectonic coals. Therefore, the results of this study contribute to understand the advantages of tectonic coal reservoirs as target sites for CO2 geological sequestration.

中文翻译：

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完整煤和构造煤的孔隙结构和扩散特征：对选择 CO2 地质封存地点的意义

摘要 随着大气中CO2 含量的增加，地质封存成为降低CO2 浓度上升的有效措施。在将 CO2 注入煤层封存 CO2 的过程中，选择合适的煤层至关重要。为了研究完整煤还是构造煤更适合CO2地质封存，采用压汞法、N2（77 K）/CO2（273 K）吸附法对这些煤样的孔隙结构特征和分形维数进行了分析，并获得了这些煤样的甲烷吸附和扩散特性。结果表明，构造煤具有较大的孔隙体积和微孔、中孔和大孔的比表面积，而构造煤的分形维数较小（即孔隙结构更简单，较小的孔隙表面粗糙度），表明构造煤具有更有利的孔隙结构，可以为 CO2 封存提供更多的吸附位点。此外，与完整煤相比，构造煤更好的连通性以及吸附和扩散能力得到显着提高，这表明 CO2 更容易在短时间内运移到构造煤的内部孔隙系统中，减少了消耗的时间。 CO2注入煤层，从而节省CO2封存成本。有趣的是，提出了一个分形概念模型来解释构造煤形成过程中原始长而复杂的孔隙转变为短而简单的孔隙，以及封闭孔隙转变为连通性孔隙的演变。所以，