HR: 0830h
AN: H21D-0862    [PDF]
TI: Influence of correlation on the permeability and on well-test interpretation of two-dimensional fractal porous and fractured media
AU: * de Dreuzy, J
EM: Jean-Raynald.de-Dreuzy@univ-rennes1.fr
AF: Geosciences Rennes, Universite de Rennes 1, Rennes, 35042 France
AU: Darcel, C
EM: c.darcel@itasca.fr
AF: ITASCA, 64 chem Mouilles, ECULLY, 69130 France
AU: Davy, P
EM: philippe.davy@univ-rennes1.fr
AF: Geosciences Rennes, Universite de Rennes 1, Rennes, 35042 France
AU: Bour, O
EM: olivier.bour@univ-rennes1.fr
AF: Geosciences Rennes, Universite de Rennes 1, Rennes, 35042 France
AB: How does correlation influence the medium hydraulic properties and the choice of the relevant modeling framework? We have investigated this question both in fractured and in porous media displaying fractal correlation pattern. In porous media, we show that fractal correlations let the equivalent permeability decrease with scale. However, their well-test response remains, on average, close to that of homogeneous media. In fractured media, observations of outcrops show that fractures are correlated at all scales of the medium and that there are also fractures of sizes ranging from the micro- to the macro-scale. Recent studies have shown that the correlation pattern is often a fractal and that the fracture-length distribution is a power law. This double-absence of characteristic length scale challenges for two reasons the use of homogenization techniques to model fractured media. We have studied the effect of these long-range heterogeneities on the fracture network connectivity and on the equivalent medium permeability. The correlation and the length distribution have opposite effects on connectivity and permeability. Increasing correlation lets connectivity and permeability decrease and conversely for the variance of the length distribution. In most cases, one of the characteristic (i.e. length or correlation) supersedes the other. There is only a small area where both characteristics have a simultaneous influence on permeability. In this latter area, the influence of the correlation remains low, more precisely a scale increase of at least 5 orders of magnitude is required to produce a permeability increase of one order of magnitude. Although the correlation pattern does not have much influence on the equivalent permeability, its influence on the flow pattern increases from negligible for networks at threshold to important for dense networks.
DE: 1829 Groundwater hydrology
DE: 5104 Fracture and flow
DE: 5114 Permeability and porosity
SC: Hydrology [H]
MN: 2003 Fall Meeting