Methane sorption on organic-rich shales over wide temperature and pressure ranges (30–120 °C, up to 25 MPa) is analyzed by the pore filling/potential theory. The supercritical Dubinin–Astakhov (SDA) sorption model using a density term instead of the pseudosaturation vapor term is extended to methane sorption isotherms of shales with high accuracy. A modified adsorption potential approach is suggested to analyze the temperature dependence of supercritical methane sorption on shales. The temperature-invariant characteristic curves are obtained using the modified adsorption potential approach. A characteristic curve equation derived from the SDA model is provided to predict sorption isotherms at other temperatures using one isotherm. The physical meaning of the characteristic curve has been discussed, and it comprehensively reflects the available pore space for methane sorption and the affinity between methane molecules and organic matter. According to methane characteristic curves of shales and clay minerals, shales in the gas window show higher affinity than shales in the oil window and clay minerals, though the clay minerals may provide comparable adsorbed volume. The adsorption characteristic energy shows a parabola-like shape with a minimum of approximately R_eq = 1.1%, which is related to the evolution of the porosity of the shales. This study advanced the fundamental understanding of the dynamic process of methane sorption on shales.

中文翻译：

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在宽温度范围内对富含有机物的页岩进行超临界甲烷吸附

通过孔隙填充/势能理论分析了在宽温度和压力范围（30–120°C，最高25 MPa）下富含有机物的页岩上的甲烷吸附。使用密度项而不是假饱和蒸汽项的超临界Dubinin–Astakhov（SDA）吸附模型可高精度地扩展到页岩的甲烷吸附等温线。提出了一种改进的吸附潜力方法来分析页岩上超临界甲烷吸附的温度依赖性。使用改进的吸附势方法获得温度不变的特性曲线。提供了从SDA模型导出的特性曲线方程式，以使用一个等温线预测其他温度下的吸附等温线。已经讨论了特性曲线的物理含义，它全面反映了可供甲烷吸附的可用孔隙空间以及甲烷分子与有机物之间的亲和力。根据页岩和粘土矿物的甲烷特征曲线，气窗中的页岩显示出比油窗和粘土矿物中的页岩更高的亲和力，尽管粘土矿物可能提供相当的吸附量。吸附特征能呈抛物线形，最小值约为R _eq = 1.1％，与页岩孔隙度的变化有关。这项研究提高了对页岩甲烷吸附动态过程的基本认识。