Stress-Dependent Fluid Flow and Permeability in Fractured Media: from Lab Experiments to Engineering Applications |
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Authors: | J Zhang W B Standifird J-C Roegiers Y Zhang |
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Affiliation: | (1) Knowledge Systems, Inc., Sugar Land, TX, U.S.A.;(2) Mewbourne School of Petroleum and Geological Engineering, The University of Oklahoma, Norman, OK, U.S.A.;(3) Shenhua Group Corp., Beijing, China |
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Abstract: | Summary. Permeability is a physical property in rocks of extreme importance in energy engineering, civil and environmental engineering,
and various areas of geology. Early on, fractures in fluid flow models were assumed to be rigid. However, experimental research
and field data confirmed that stress-deformation behavior in fractures is a key factor governing their permeability tensor.
Although extensive research was conducted in the past, the three-dimensional stress-permeability relationships, particularly
in the inelastic deformation stage, still remain unclear. In this paper, laboratory experiments conducted on large concrete
blocks with randomly distributed fractures and rock core samples are reported to investigate fluid flow and permeability variations
under uniaxial, biaxial and triaxial complete stress-strain process. Experimental relationships among flowrate, permeability
and fracture aperture in the fractured media are investigated. Results show that the flowrate and stress/aperture exhibit
“cubic law” relationship for the randomly distributed fractures.
A permeability-aperture relationship is proposed according to the experimental results. Based on this relationship, stress-dependent
permeability in a set of fractures is derived in a three-dimensional domain by using a coupled stress and matrix-fracture
interactive model. A double porosity finite element model is extended by incorporating such stress-dependent permeability
effects. The proposed model is applied to examine permeability variations induced by stress redistributions for an inclined
borehole excavated in a naturally fractured formation. The results indicate that permeability around underground openings
depends strongly on stress changes and orientations of the natural fractures. |
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Keywords: | : Permeability stress fluid flow fracture aperture fractured media borehole |
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