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煤/页岩中甲烷的吸附—扩散性能是煤层气/页岩气资源评价的关键参数之一。通过对晋城矿区寺河井田二叠系山西组3号煤层样和华南古生界下志留统龙马溪组页岩样进行低温液氮和甲烷等温吸附实验,剖析了高演化富有机质页岩和高煤阶煤中甲烷的吸附—扩散性能,建立了煤/页岩中甲烷的吸附—扩散性模型,对比分析了煤/页岩中甲烷的吸附—扩散性能的差异性和控制机理。结果表明,高演化富有机质页岩样和高煤阶煤样的孔容均主要由介孔和大孔贡献,比表面积主要由微孔和介孔贡献,且高演化富有机质页岩样纳米孔隙更发育,比表面积和孔容要大于煤样。高演化富有机质页岩和高煤阶煤中甲烷的吸附和扩散规律服从Langmuir方程,高演化富有机质页岩中甲烷吸附性能明显低于高煤阶煤,且随着高演化富有机质页岩TOC含量的增加而增高;但其对甲烷扩散性能要高于高煤阶煤一个数量级。高演化富有机质页岩样中孔隙多为开放型,而高阶煤基质孔隙多为半封闭型。对于半封闭型孔隙,强吸附质的溶入会改变吸附剂的大分子结构,其吸附与解吸过程不是可逆的,存在解吸滞后现象,导致高演化富有机质页岩与高煤阶煤中甲烷解吸—扩散过程与扩散—吸附过程中的扩散性能差异性。
Adsorption-diffusion properties of methane in coal / shale are one of the key parameters for CBM / shale gas assessment. Through the experiments of low temperature liquid nitrogen and methane isothermal adsorption experiments on the No.3 coal seam of Permian Shanxi Formation and the Lower Silurian Longmaxi shale in South China Paleozoic in Jincheng mining area, Adsorption-diffusion properties of methane in high-rank coal and the adsorption-diffusion model of methane in coal / shale are established. The differences and control mechanisms of methane adsorption / diffusion in coal / shale are compared and analyzed. The results show that the pore volume of highly-evolved organic-rich shale samples and high-rank coal samples are mainly contributed by mesopores and macropores, and the specific surface area is mainly contributed by micropores and mesopores. Moreover, the highly evolved organic-rich shale- Specific surface area and pore volume should be greater than the coal sample. The adsorption and diffusion of methane in highly-evolved organic-rich shale and high-rank coal obey the Langmuir equation, and the methane adsorption in high-evolution organic-rich shale is significantly lower than that in high-rank coal. With the increase of TOC But the methane diffusion performance is higher than that of high rank coal. Most of the pores in high-evolution organic-rich shale samples are open types, while most of the pores in higher-grade coal-derived ones are mostly semi-closed types. For semi-closed pores, the strong adsorbate will change the macromolecular structure of the adsorbent. The adsorption and desorption processes are not reversible, and there exists the phenomenon of desorption and hysteresis, leading to the desorption of methane from high-evolution organic-rich shale and coal with high rank Diffusion Diffusion in Diffusion and Adsorption Process.