Backeberg Nils R, Iacoviello Francesco, Rittner Martin, Mitchell Thomas M, Jones Adrian P, Day Richard, Wheeler John, Shearing Paul R, Vermeesch Pieter, Striolo Alberto
University College London, Department of Earth Sciences, London, WC1E 6BT, UK.
University College London, Electrochemical Innovation Lab, Department of Chemical Engineering, London, WC1E 6BT, UK.
Sci Rep. 2017 Nov 1;7(1):14838. doi: 10.1038/s41598-017-14810-1.
The permeability of shales is important, because it controls where oil and gas resources can migrate to and where in the Earth hydrocarbons are ultimately stored. Shales have a well-known anisotropic directional permeability that is inherited from the depositional layering of sedimentary laminations, where the highest permeability is measured parallel to laminations and the lowest permeability is perpendicular to laminations. We combine state of the art laboratory permeability experiments with high-resolution X-ray computed tomography and for the first time can quantify the three-dimensional interconnected pathways through a rock that define the anisotropic behaviour of shales. Experiments record a physical anisotropy in permeability of one to two orders of magnitude. Two- and three-dimensional analyses of micro- and nano-scale X-ray computed tomography illuminate the interconnected pathways through the porous/permeable phases in shales. The tortuosity factor quantifies the apparent decrease in diffusive transport resulting from convolutions of the flow paths through porous media and predicts that the directional anisotropy is fundamentally controlled by the bulk rock mineral geometry. Understanding the mineral-scale control on permeability will allow for better estimations of the extent of recoverable reserves in shale gas plays globally.
页岩的渗透率很重要，因为它控制着油气资源能够迁移到的位置以及地球内部碳氢化合物最终储存的位置。页岩具有众所周知的各向异性方向渗透率，这是从沉积纹层的沉积分层继承而来的，其中平行于纹层测量的渗透率最高，垂直于纹层测量的渗透率最低。我们将最先进的实验室渗透率实验与高分辨率X射线计算机断层扫描相结合，首次能够量化穿过岩石的三维连通路径，这些路径定义了页岩的各向异性行为。实验记录了渗透率在一到两个数量级上的物理各向异性。对微米和纳米尺度X射线计算机断层扫描的二维和三维分析揭示了页岩中多孔/渗透相的连通路径。曲折因子量化了由于流经多孔介质的流路卷积导致的扩散传输的明显降低，并预测方向各向异性从根本上受块状岩石矿物几何形状控制。了解渗透率的矿物尺度控制将有助于更好地估计全球页岩气藏中可采储量的范围。
