Understanding the mechanisms of shale–water interaction by water vapour adsorption is crucial for predicting shale gas productivity. In this study, equilibrium adsorption data of water vapour on four different shales of the Sichuan Basin at three temperatures (298, 308, and 318 K) were measured using static gravity techniques. The water vapour adsorption isotherms were simulated by three statistical physics models. Steric parameters, including the number of water vapour molecules adsorbed per site (n), monolayer adsorption amount (q0), and adsorption energy (ΔEa), and thermodynamic parameters such as configuration entropy (Sa), internal energy (Eint), and free energy (Ga) derived from the selected model were used to explain the adsorption mechanism. The model analyses suggest that the adsorbed water vapour molecules are attached to the shale surface in a multi‐anchorage manner. The adsorption of the first layer shows a Type I characteristics, while the adsorption of the subsequent layer is of Type III. The calculated adsorption energies indicate that the physical adsorption takes place on the water vapour molecules on the shale, and the main interaction forces are hydrophilic bonding forces and van der Waals forces. Negative Eint and Ga values indicate that the spontaneous properties are for water vapour adsorption and that the system requires the release of energy to capture the water vapour molecules.

中文翻译：

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页岩上水蒸气吸附等温线的统计物理模型：立体、能量和热力学研究

了解页岩与水通过水蒸气吸附相互作用的机制对于预测页岩气产能至关重要。在这项研究中，利用静态重力技术测量了四川盆地四种不同页岩在三个温度（298、308和318 K）下的水蒸气平衡吸附数据。通过三个统计物理模型模拟水蒸气吸附等温线。位阻参数，包括每个位点吸附的水蒸气分子的数量（n)、单分子层吸附量(q0）和吸附能（Δ乙A）和热力学参数，例如构型熵（SA）， 内能 （乙整数）和自由能（GA）从所选模型导出用于解释吸附机制。模型分析表明，吸附的水蒸气分子以多锚固方式附着在页岩表面。第一层的吸附呈现I型特征，而后续层的吸附呈现III型特征。计算的吸附能表明页岩上的水蒸气分子发生物理吸附，主要相互作用力是亲水键合力和范德华力。消极的乙整数和GA值表明自发特性用于水蒸气吸附，并且系统需要释放能量来捕获水蒸气分子。