In a context of growing attention for shale gas, the precise impact of organic matter (kerogen) on hydrocarbon recovery from unconventional reservoirs still has to be assessed. Kerogen’s microstructure is characterized by a very disordered pore network that greatly affects hydrocarbon transport. The specific structure and texture of this organic matter at the nanoscale is highly dependent on its origin. In this study, by the use of statistical physics and molecular dynamics, we shed some new lights on hydrocarbon transport through realistic molecular models of kerogen at different level of maturity [Bousige et al. Nat. Mater. 2016, 15, 576]. Despite the apparent complexity, severe confinement effects controlled by the porosity of the various kerogens allow linear alkanes (from methane to dodecane) transport to be studied only via the self-diffusion coefficients of the species. The decrease of the transport coefficients with the amount of adsorbed fluid can be described by a free volume theory. Ultimately, the transport coefficients of hydrocarbons can be expressed simply as a function of the porosity (volume fraction of void) of the microstructure, thus paving the way for shale gas recovery predictions.

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页岩有机质中纳米孔隙对烃输运的影响

在页岩气日益受到关注的背景下，有机物（干酪根）对非常规油藏油气开采的确切影响仍然有待评估。干酪根的微观结构的特征是非常无序的孔隙网络，极大地影响了碳氢化合物的运输。这种有机物在纳米级的特定结构和质地高度取决于其来源。在这项研究中，通过使用统计物理学和分子动力学，我们通过不同成熟度的干酪根的真实分子模型为烃输运提供了一些新的思路[布西格等。纳特 母校 2016，15，576]。尽管表面上很复杂，但受各种干酪根的孔隙率控制的严格限制效应仅允许通过物种的自扩散系数研究线性烷烃（从甲烷到十二烷）的运输。输运系数随吸附流体量的减少可以通过自由体积理论来描述。最终，碳氢化合物的输运系数可以简单地表示为微观结构的孔隙率（孔隙的体积分数）的函数，从而为页岩气的采收率预测铺平了道路。