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Schlagwörter:
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Zusammenfassung:
In subsurface projects where the host rock is of low permeability, fractures play an important role in fluid
circulation. Both the geometrical and mechanical properties of the fracture are relevant to the perme-
ability of the fracture. To evaluate this relationship, we numerically generated self-affine fractures
reproducing the scaling relationship of the power spectral density (PSD) of the measured fracture sur-
faces. The fractures were then subjected to a uniform and stepwise increase in normal stress. A fast
Fourier transform (FFT)-based elastic contact model was used to simulate the fracture closure. The
evolution of fracture contact area, fracture closure, and fracture normal stiffness were determined
throughout the whole process. In addition, the fracture permeability at each step was calculated by the
local cubic law (LCL). The influences of roughness exponent and correlation length on the fracture hy-
draulic and mechanical behaviors were investigated. Based on the power law of normal stiffness versus
normal stress, the corrected cubic law and the linear relationship between fracture closure and me-
chanical aperture were obtained from numerical modeling of a set of fractures. Then, we derived a
fracture normal stiffness-permeability equation which incorporates fracture geometric parameters such
as the root-mean-square (RMS), roughness exponent, and correlation length, which can describe the
fracture flow under an effective medium regime and a percolation regime. Finally, we interpreted the
flow transition behavior from the effective medium regime to the percolation regime during fracture
closure with the established stiffness-permeability function.
