Abstract The tortuosity of kerogen pore structures is a vital parameter in the quantification of the gas diffusion ability and production of shale reservoirs. In this study, we perform a molecular dynamics simulation on the gas diffusion in the molecular- and nano-scale pores of shale kerogen to evaluate the tortuosity of the kerogen pore structure to gas diffusion. A novel diffusion model is proposed to evaluate the tortuosity by considering gas adsorption affinity, transportation regime, and probe gas atomic size. The results indicate that the tortuosity of the kerogen pore structure to gas diffusion is not a constant; instead, it highly depends on the probe gas atomic size and gas adsorption ability. The diffusive tortuosity is overestimated when the effect of gas adsorption ability is ignored. We find that the electrical tortuosity is lower than the diffusive tortuosity. This confirms that the tortuosity is underestimated when considering a purely geometric effect.

中文翻译：

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干酪根孔隙结构对分子和纳米尺度气体扩散的曲折性：分子动力学模拟

摘要 干酪根孔隙结构的曲折度是量化页岩储层气体扩散能力和产量的重要参数。在这项研究中，我们对页岩干酪根分子和纳米级孔隙中的气体扩散进行了分子动力学模拟，以评估干酪根孔隙结构对气体扩散的曲折性。提出了一种新的扩散模型，通过考虑气体吸附亲和力、运输方式和探测气体原子大小来评估曲折度。结果表明，干酪根孔隙结构对气体扩散的曲折度不是一个常数；相反，它在很大程度上取决于探测气体的原子大小和气体吸附能力。当忽略气体吸附能力的影响时，高估了扩散迂曲度。我们发现电迂曲度低于扩散迂曲度。这证实了在考虑纯几何效应时会低估曲折度。