Direct measurement of contact area and stress dependence of anisotropic flow through rock fracture with heterogeneous aperture distribution
Direct measurement of contact area and stress dependence of anisotropic flow through rock fracture with heterogeneous aperture distribution
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DOI：
10.1016/j.epsl.2009.02.005
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发表时间：
2009-04-30
影响因子：
5.3
通讯作者：
Tsuchiya, Noriyoshi
中科院分区：
文献类型：
--
作者：
Nemoto, Katsumi;Watanabe, Noriaki;Tsuchiya, Noriyoshi
利用压敏薄膜直接测量了不同剪切位移2、3和5 mm、不同正应力高达100 Mpa的人工花岗岩拉伸裂缝的接触面积，以阐明剪切位移岩石裂缝中各向异性流动与正应力之间的关系。然后利用裂隙表面几何数据数值生成具有接触面积的孔径分布，并通过双向流动模拟来评估各向异性流动。在每个给定的条件下，都可以清楚地观察到接触粗糙在断裂面上的方向分布，并且接触粗糙在垂直于剪切位移的方向上趋于对齐。一般情况下，随着正应力的增大，接触面积增大，各向异性分布增强。然而，当>；=3 mm剪切位移时，接触面积与应力的相关性较小。在垂直方向上具有较高渗透率的各向异性流动，其孔径分布与接触的凹凸体呈各向异性分布。由于接触粗糙度的分布，在孔径分布中形成的流动路径在垂直方向上看起来不那么曲折。裂隙的各向异性流动随法向应力的增加而增强，并且由于接触区对法向应力的敏感性较高，当剪切位移较小时，各向异性流动更加明显。结果表明，各向异性流动可能存在较大范围的正应力(相应地，在地壳的不同深度)，在该范围内，各向异性流动随着接触区的应力依赖性而增加。此外，对于更高的正应力，应力依赖的各向异性流动是预期的，因为在几到一万米深的地应力条件下，100%接触面积的裂缝完全闭合可能是意想不到的。(C)2009爱思唯尔B.V.保留所有权利。
Direct measurement of a contact area using pressure-sensitive film was performed for artificially generated granite tensile fractures, with different shear displacements of 2,3, and 5 mm and at various normal stresses of up to approximately 100 MPa, to clarify the relationship between anisotropic flow and normal stress in a rock fracture with shear displacement. Aperture distributions with contact areas were then numerically generated using fracture surface geometry data, and anisotropic flow was evaluated through a bi-directional flow simulation. The directional distributions of contacting asperities in the fracture plane were clearly observed for every given condition and the contacting asperities tended to align in the direction perpendicular to shear displacement. Generally, the contact area increased and the anisotropic distribution was enhanced with increasing normal stress. However, the contact areas for >= 3 mm shear displacement were less stress dependent. Anisotropic flow with higher permeability in the perpendicular direction was always observed for aperture distributions with an anisotropic distribution of the contacting asperities. Flow paths created in the aperture distributions seemed less tortuous in the perpendicular direction due to the distribution of the contacting asperities. The anisotropic flow was enhanced with increasing normal stress to the fracture, and was more evident for the smaller shear displacements of 2 mm due to the high sensitivity of the contact area to the normal stress. The results suggested that the anisotropic flow was likely for a wide range of normal stresses (and correspondingly, at varying depths in the Earth's crust), at which anisotropic flow was enhanced with increasing normal stress based on the stress dependence of the contact area. In addition, the stress dependent anisotropic flow is expected for much higher normal stresses because complete fracture closure with 100% contact area may be unexpected under the crustal stress conditions at depths of several to ten thousand meters. (C) 2009 Elsevier B.V. All rights reserved.