Abstract Tremendous amount of gas can be adsorbed in shale nanopores as a result of the high surface-to-volume ratio, and capillary condensation might occur in mesopores (2–50 nm) for subcritical gases, leading to sorption hysteresis. However, the sorption (adsorption and desorption) behavior in different pore systems in shale is not very well understood. Herein we use a D3Q19 lattice Boltzmann model (LBM) that incorporates the mesoscopic fluid-fluid and solid-fluid interactions to study sorption hysteresis in nanopores. The model is developed based on our previous work using a D2Q9 LBM, and is calibrated to lattice density functional theory (LDFT). Improved thermodynamic consistency is observed using exact difference method and tunable interparticle forcing scheme. Sorption simulation in an open and semi-closed slit pore shows different extent of hysteresis, which is in good agreement with Grand Canonical Monte Carlo simulation (GCMC) results. We then reconstruct two types of nanopore systems that are commonly observed in shale, namely the interparticle and intraparticle pores, and study and compare nitrogen sorption hysteresis. The spatial distribution of the condensed nitrogen is visualized and two distinct types of sorption hysteresis loops based on the classification by International Union of Pure and Applied Chemistry (IUPAC) are observed, which indicates that the experimentally measured nitrogen sorption curves can be used to distinguish the dominant pore type in shale. The 3D LBM developed in this study can be used to explore a wide variety of thermodynamic processes that happen at nanoscale, and it can also be incorporated with hydrodynamics to study coupled problems of fluid adsorption/transport in shale.

中文翻译：

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使用格子 Boltzmann 方法对页岩纳米孔中的气体吸附滞后进行孔尺度研究

摘要 由于页岩纳米孔的高表面积与体积比，可以吸附大量气体，亚临界气体的介孔（2-50 nm）可能发生毛细管冷凝，导致吸附滞后。然而，页岩中不同孔隙系统的吸附（吸附和解吸）行为还不是很清楚。在此，我们使用 D3Q19 晶格玻尔兹曼模型 (LBM)，该模型结合了细观流体-流体和固-流体相互作用来研究纳米孔中的吸附滞后。该模型是基于我们之前使用 D2Q9 LBM 的工作开发的，并根据晶格密度泛函理论 (LDFT) 进行校准。使用精确差分法和可调粒子间强迫方案观察到改进的热力学一致性。开放和半封闭狭缝孔中的吸附模拟显示出不同程度的滞后，这与 Grand Canonical Monte Carlo 模拟 (GCMC) 结果非常吻合。然后，我们重建了页岩中常见的两种纳米孔系统，即颗粒间和颗粒内孔，并研究和比较了氮吸附滞后。冷凝氮的空间分布可视化，并观察到基于国际纯粹与应用化学联合会 (IUPAC) 分类的两种不同类型的吸附滞后回线，这表明实验测量的氮吸附曲线可用于区分页岩中占优势的孔隙类型。本研究中开发的 3D LBM 可用于探索在纳米尺度上发生的各种热力学过程，