Frequency- and incident-angle-dependent P-wave properties influenced by dynamic stress interactions in fractured porous media

Abstract

The effect of stress interactions on the effective poroelastic properties in saturated porous media has not been well-understood, especially for rocks with a fracture density larger than the dilute limit assumption. Frequency- and angle-dependent characteristics of stress interactions are analyzed by finite-element numerical tests with a least-squares procedure. We have investigated two types of fractured media: a stacked fractured model with stress shielding and a coplanar fractured model with stress amplification. We evaluate the effect of stress interactions from different spatial distributions of fractures on seismic attenuation and dispersion, with a specific focus on their frequency- and angle-dependent characteristics. We determine with numerical examples that a greater shielding effect corresponds to a larger frequency corresponding to maximum attenuation but a smaller peak attenuation. In contrast, a larger amplification effect leads to a higher attenuation. Due to the excluded diffusion energy outside the representative volume element, increasing the incidence angle ([Formula: see text]) leads to decreasing attenuation, whereas stress amplification is enhanced as the incidence angle increases continuously ([Formula: see text]), corresponding to increasing attenuation. This suggests that different incidence angles reshape the spatial distribution of stress interactions, in turn contributing to different frequency-dependent behaviors.