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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Network modeling of the evolution of permeability
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Network modeling of the evolution of permeability

机译：渗透性演化的网络建模

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Rock deformation and fluid transport are coupled together in many crustal settings. Nonhydrostatic stress can greatly affect pore structure and transport properties of a rock. When a compact rock is stressed to failure, dilatancy and permeability enhancement are generally observed whether the failure mode is brittle faulting or cataclastic flow. Laboratory data for the brittle faulting regime (in Westerly granite) and for the cataclastic flow regime (in Carrara marble and synthetic halite) are modeled. Dilatancy is simulated by incorporating an increasing number of stress-induced microcracks with similar geometric attributes in a random network model, thus enhancing permeability. The microcracks are represented by sheet-like conduits, with crack length and aspect ratio distributions constrained by microstructural data. Before the onset of dilatancy, a rock under overall compression has very low density of open cracks that occur in isolated clusters with relatively low connectivity. Nonhydrostatic loading induces damage in the form of extensile microcracks that gradually form a fully connected percolation network. Significant permeability increase of up to several orders of magnitude may occur in this percolative regime. Once the crack network is fully connected, the accumulation of additional cracks is not as effective in enhancing permeability, and our model predicts permeability and porosity changes to be linearly related in this fully connected regime. After accounting for the existence of fine cracks that are below the microscope resolution, our simulation results agree reasonably well in laboratory data.
机译：岩石变形和流体输送在许多地壳环境中耦合在一起。非静水应力会极大地影响岩石的孔隙结构和传输特性。当致密岩石受到破坏时，无论破坏模式是脆性断裂还是碎裂流，通常都会观察到膨胀性和渗透率的提高。模拟了脆性断层状态（在韦斯特里花岗岩中）和碎裂流动状态（在卡拉拉大理石和合成岩盐中）的实验室数据。通过在随机网络模型中并入越来越多的具有相似几何属性的应力诱发微裂纹来模拟扩张，从而提高渗透率。微裂纹以片状导管为代表，裂纹长度和长宽比分布受微结构数据约束。在膨胀开始之前，在整体压缩下的岩石具有非常低的开放裂缝密度，这些裂缝出现在连接性相对较低的孤立簇中。非静水载荷以可扩展的微裂纹形式逐渐形成完全连接的渗滤网络，从而引起破坏。在这种渗流状态下，渗透率可能会显着增加几个数量级。裂纹网络完全连接后，附加裂纹的累积不能有效提高渗透率，并且我们的模型预测，在这种完全连接的状态下，渗透率和孔隙率变化呈线性关系。考虑到存在低于显微镜分辨率的细裂纹后，我们的模拟结果在实验室数据中相当吻合。

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