Numerical considerations of fluid effects on wave propagation: Influence of the tortuosity

Abstract

The focus of this paper is on effective elastic properties (i.e., velocities) in three different kinds of dry and fluidsaturated porous media. The synthetic results are compared with the predictions of the Gassmann equation and the tortuosity-dependent high-frequency limit of the Biot velocity relations. Using a dynamic finite-difference approach we observe for Fontainebleau sandstone the same effective elastic properties as with a static finite-element approach. We show that so-called open-cell Gaussian random field models are similar in mechanical properties to Fontainebleau sandstone. For all synthetic models considered in this study the high-frequency limit of the Biot velocity relations is very close to the predictions of the Gassmann equation. However, using synthetic rockmodels saturated with an imaginary fluid of high density we can approximately estimate the corresponding tortuosity parameter. Copyright 2004 by the American Geophysical Union.