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pure and applied geophysics

, Volume 131, Issue 1–2, pp 111–138 | Cite as

The fractal geometry of flow paths in natural fractures in rock and the approach to percolation

  • D. D. Nolte
  • L. J. Pyrak-Nolte
  • N. G. W. Cook
Article

Abstract

The distributions of contact areas in single, natural fractures in quartz monzonite (Stripa granite) are found to have fractal dimensions which decrease fromD=2.00 to values nearD=1.96 as stress normal to the fractures is increased from 3 MPa up to 85 MPa. The effect of stress on fluid flow is studied in the same samples. Fluid transport through a fracture depends on two properties of the fracture void space geometry. the void aperture; and the tortuosity of the flow paths, determined through the distribution of contact area. Each of these quantities change under stress and contribute to changes observed in the flow rate. A general flow law is presented which separates these different effects. The effects of tortuosity on flow are largely governed by the proximity of the flow path distribution to a percolation threshold. A fractal model of correlated continuum percolation is presented which quantitatively reproduces the flow path geometries. The fractal dimension in this model is fit to the measured fractal dimensions of the flow systems to determine how far the flow systems are above the percolation threshold.

Key words

Fractals fractures fluid flow percolation rock mechanics geohydrology 

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Copyright information

© Birkhäuser-Verlag 1989

Authors and Affiliations

  • D. D. Nolte
    • 1
  • L. J. Pyrak-Nolte
    • 2
  • N. G. W. Cook
    • 2
  1. 1.Department of PhysicsUniversity of CaliforniaBerkeleyUSA
  2. 2.Department of Material Science and Mineral EngineeringUniversity of CaliforniaBerkeleyUSA

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