Falk Kerstin, Coasne Benoit, Pellenq Roland, Ulm Franz-Josef, Bocquet Lydéric
Department of Civil and Environmental Engineering and MultiScale Material Science for Energy and Environment UMI 3466 CNRS-MIT, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Nat Commun. 2015 Apr 22;6:6949. doi: 10.1038/ncomms7949.
Although hydrocarbon production from unconventional reservoirs, the so-called shale gas, has exploded recently, reliable predictions of resource availability and extraction are missing because conventional tools fail to account for their ultra-low permeability and complexity. Here, we use molecular simulation and statistical mechanics to show that continuum description--Darcy's law--fails to predict transport in shales nanoporous matrix (kerogen). The non-Darcy behaviour arises from strong adsorption in kerogen and the breakdown of hydrodynamics at the nanoscale, which contradict the assumption of viscous flow. Despite this complexity, all permeances collapse on a master curve with an unexpected dependence on alkane length. We rationalize this non-hydrodynamic behaviour using a molecular description capturing the scaling of permeance with alkane length and density. These results, which stress the need for a change of paradigm from classical descriptions to nanofluidic transport, have implications for shale gas but more generally for transport in nanoporous media.
尽管来自非常规储层的烃类生产，即所谓的页岩气，近年来呈爆发式增长，但由于传统工具无法考虑其超低渗透率和复杂性，因此缺乏对资源可用性和开采的可靠预测。在此，我们使用分子模拟和统计力学表明，连续介质描述——达西定律——无法预测页岩纳米多孔基质（干酪根）中的输运。非达西行为源于干酪根中的强吸附以及纳米尺度流体动力学的失效，这与粘性流动的假设相矛盾。尽管存在这种复杂性，但所有渗透率都汇聚在一条主曲线上，且对烷烃长度有意外的依赖性。我们使用一种分子描述来解释这种非流体动力学行为，该描述捕捉了渗透率与烷烃长度和密度的标度关系。这些结果强调了从经典描述向纳米流体输运转变范式的必要性，对页岩气有影响，但更普遍地对纳米多孔介质中的输运也有影响。
