One attractive aspect of CO2 sequestration in shale formations is the preferential adsorption of CO2 compared to methane, which may provide enhanced methane production as well as sequestration of carbon dioxide. In this work, a comprehensive theoretical model of CO2 migration at the pore scale is developed to study CO2 migration properties in organic-rich shale formations. The proposed model takes into account dynamic competitive adsorption between CO2 and CH4, slip-flow effects due to the nanometer range of pore sizes, and pore-size changes due to adsorption. Because of the high pressure and temperature, the injected CO2 is in supercritical phase. Pore bodies in the shale matrix are irregular in shape, with roughness along pore wall. The structure of pore body affects the amount of surface areas and associated number of adsorption sites, and hence, a shape factor is proposed in this work to consider the irregularity of pore structure in shale matrix. The sorption of CO2 leads to an apparent retardation of the migration of CO2, which is quantified in this work. The developed pore-network model is extended to consider the impacts of different spatial distributions of the organic materials within the shale matrix.

中文翻译：

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富含有机质页岩地层中 CO2 动态运移的孔隙网络模拟模型

页岩地层中 CO2 封存的一个吸引人的方面是与甲烷相比优先吸附 CO2，这可以提高甲烷产量并封存二氧化碳。在这项工作中，开发了孔隙尺度 CO2 运移的综合理论模型，以研究富含有机质页岩地层中的 CO2 运移特性。所提出的模型考虑了 CO2 和 CH4 之间的动态竞争吸附、纳米孔径范围引起的滑流效应以及吸附引起的孔径变化。由于高压和高温，注入的 CO2 处于超临界相。页岩基质中的孔体形状不规则，沿孔壁粗糙。孔体的结构影响表面积的大小和相关的吸附位点数，因此，在这项工作中提出了一个形状因子来考虑页岩基质中孔隙结构的不规则性。CO2 的吸附导致 CO2 迁移的明显延迟，这在本工作中进行了量化。开发的孔隙网络模型被扩展以考虑页岩基质内有机材料的不同空间分布的影响。