A test of the effectiveness of pore scale fluid flow simulations and constitutive equations for modelling the effects of mineral dissolution on rock permeability
A test of the effectiveness of pore scale fluid flow simulations and constitutive equations for modelling the effects of mineral dissolution on rock permeability
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DOI：
10.1016/j.chemgeo.2018.03.020
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发表时间：
2018-04
期刊：
影响因子：
3.9
通讯作者：
B. Lamy-Chappuis;Bruce W. D. Yardley;S. He;Yingqing Zu;Jianfei Xie
中科院分区：
文献类型：
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作者：
B. Lamy-Chappuis;Bruce W. D. Yardley;S. He;Yingqing Zu;Jianfei Xie
岩石的宏观尺度输运性质，如渗透率，是结合了仅在孔隙尺度上适当定义的各种性质的贡献的整体参数。由于已知孔隙尺度过程会改变岩石性质，因此合理地询问基于宏观尺度性质（例如孔隙度、渗透率、地层因素等）的本构方程是否可以适当地描述其效果。在先前的实验研究（Lamy-Chappuis等人，2014），我们发现矿物溶解对渗透率的影响可能远高于这种半经验本构方程预测的。在这里，我们直接在矿物溶解前后岩石几何形状的高分辨率（2.5 μm）3D模型中求解孔隙尺度流体流动，以评估渗透率及其变化。这种方法受到用于定义岩石几何形状的微CT图像的分辨率的限制，这导致绝对渗透率的显著高估，但它确实产生了比本构方程更接近矿物溶解引起的渗透率变化的匹配。这是可能的，因为提高渗透性的溶解特征足够大，足以被充分解析并产生渗透性的显著变化。
Macro-scale transport properties of rocks such as permeability are bulk parameters combining the contributions of various properties only properly defined at the pore scale. Since pore-scale processes are known to modify the rock properties it is legitimate to ask if constitutive equations based on macro scale properties (e.g. porosity, permeability, formation factor, etc…) can properly describe their effect. In a previous experimental study (Lamy-Chappuis et al., 2014) we found that the effect of mineral dissolution on permeability could be much higher than predicted by such semi-empirical constitutive equations. Here we directly solve pore-scale fluid flow in high-resolution (2.5 μm) 3D models of a rock's geometry before and after mineral dissolution in order to evaluate permeability and how it is changed. This methodology is limited by the resolution of the micro-CT images used to define the rock geometry, which leads to significant overestimates of absolute permeability, but it does produce a much closer match to the change in permeability due to mineral dissolution than the constitutive equations. This is possible because the dissolution features, which enhance permeability, are large enough to be adequately resolved and produce a significant change in permeability.