Size effect on aperture and permeability of a fracture as estimated in large synthetic fractures
Size effect on aperture and permeability of a fracture as estimated in large synthetic fractures
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DOI：
10.1016/j.ijrmms.2005.12.001
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发表时间：
2006-07
影响因子：
7.2
通讯作者：
K. Matsuki;Y. Chida;K. Sakaguchi;P. Glover
中科院分区：
文献类型：
--
作者：
K. Matsuki;Y. Chida;K. Sakaguchi;P. Glover
用一种新的频谱方法在计算机上创建了尺寸从0.2到12.8m的合成骨折，以再现初始孔径(当表面在单点接触时的孔径)的功率谱密度与1m拉伸骨折的表面高度的比率。首先，分析了有剪切裂缝和无剪切裂缝的初始孔径标准差的尺寸效应。其次，通过每隔一段时间取孔径数据建立流区，通过求解雷诺方程确定水力孔径，模拟裂缝正常闭合和剪切后闭合时的水流情况。当裂缝闭合而不剪切且具有相同的平均孔径时，如果裂缝大于约0.2m，则裂缝尺寸对水力孔径的影响消失，因为超过该尺寸，初始孔径的标准偏差几乎与裂缝尺寸无关。当裂缝在剪切后闭合时，渗透系数表现出明显的各向异性，并且随着剪切位移和闭合的增加而变得更加明显。然而，当剪切位移小于裂缝尺寸的3.1%时，由平均孔径归一化的水力孔径与由初始孔径的标准差归一化的平均孔径之间的关系几乎与裂缝尺寸和剪切位移无关，此时剪切裂缝的初始孔径的标准差几乎与裂缝尺寸无关。
Synthetic fractures of from 0.2 to 12.8m in size were created on a computer by a new spectral method to reproduce the ratio of the power spectral density of the initial aperture (the aperture when the surfaces are in contact at a single point) to that of the surface height determined for a tensile fracture of 1m. First, the size effect on the standard deviation of the initial aperture was analyzed for fractures with and without shearing. Next, by taking aperture data at constant intervals to establish a flow area, water flow was simulated for fractures during both normal closure and closure after shearing, by solving Reynolds equation to determine the hydraulic aperture. When the fracture is closed without shearing and has the same mean aperture, the effect of the fracture size on the hydraulic aperture disappears if the fracture is larger than about 0.2m, since beyond this size the standard deviation of the initial aperture is almost independent of the fracture size. When the fracture is closed after shearing, the hydraulic conductivity shows remarkable anisotropy, which becomes more significant with both shear displacement and closure. However, the relation between the hydraulic aperture normalized by the mean aperture and the mean aperture normalized by the standard deviation of the initial aperture is almost independent of both the fracture size and shear displacement when the shear displacement is less than about 3.1% of the fracture size, at which point the standard deviation of the initial aperture of the sheared fracture is almost independent of the fracture size.