Influence of fracture scale heterogeneity on the flow properties of three-dimensional discrete fracture networks (DFN)
While permeability scaling of fractured media has been so far studied independently at the fracture‐ and network‐ scales, we propose a numerical analysis of the combined effect of fracture‐scale heterogeneities and the network‐scale topology. The analysis is based on 2·106discrete fracture network (...
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Published in | Journal of Geophysical Research: Solid Earth Vol. 117; no. B11 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Washington, DC
Blackwell Publishing Ltd
01.11.2012
American Geophysical Union |
Subjects | |
Online Access | Get full text |
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Summary: | While permeability scaling of fractured media has been so far studied independently at the fracture‐ and network‐ scales, we propose a numerical analysis of the combined effect of fracture‐scale heterogeneities and the network‐scale topology. The analysis is based on 2·106discrete fracture network (DFNs) simulations performed with highly robust numerical methods. Fracture local apertures are distributed according to a truncated Gaussian law, and exhibit self‐affine spatial correlations up to a cutoff scaleLc. Network structures range widely over sparse and dense systems of short, long or widely distributed fracture sizes and display a large variety of fracture interconnections, flow bottlenecks and dead‐ends. At the fracture scale, accounting for aperture heterogeneities leads to a reduction of the equivalent fracture transmissivity of up to a factor of 6 as compared to the parallel plate of identical mean aperture. At the network scale, a significant coupling is observed in most cases between flow heterogeneities at the fracture and at the network scale. The upscaling from the fracture to the network scale modifies the impact of fracture roughness on the measured permeability. This change can be quantified by the measureα2,which is analogous to the more classical power‐averaging exponent used with heterogeneous porous media, and whose magnitude results from the competition of two effects: (i) the permeability is enhanced by the highly transmissive zones within the fractures that can bridge fracture intersections within a fracture plane; (ii) it is reduced by the closed and low transmissive areas that break up connectivity and flow paths.
Key Points
Combined effect of fracture heterogeneity and network topology on permeability
Generalization of power‐averaging for truncated Gaussian permeability fields
Permeability reduction by self‐affine correlated fracture aperture distribution |
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Bibliography: | ArticleID:2012JB009461 istex:BD9E65781BF82596B0CC308150F147E0085BE225 ark:/67375/WNG-X1XJ345N-8 Tab-delimited Table 1. |
ISSN: | 0148-0227 2169-9313 2156-2202 2169-9356 |
DOI: | 10.1029/2012JB009461 |