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 ([ ]) leads to decreasing attenuation, whereas stress amplification is enhanced as the incidence angle increases continuously ([ ]), 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.

Open or partially open boundary conditions in fully or partially saturated rocks possibly occur in many realistic geologic scenarios, and it is critical to understand the influences of wave...

Generally, local stress induced by individual crack hardly disturbs their neighbors for small crack densities, which, however, could not be neglected as the crack density increases. The disturbance becomes rather complex in saturated porous rocks due to the wave‐induced diffusion of fluid pressures. The problem is addressed in this study by the comparison of two solutions: the analytical solution without stress interactions and the numerical method with stress interactions. The resultant difference of effective properties can be used to estimate the effect of stress interactions quantitatively. Numerical experiments demonstrate that the spatial distribution pattern of cracks strongly affects stress interactions. For regularly distributed cracks, the resulting stress interaction (shielding or amplification) shows strong anisotropy, depending on the arrangement and density of cracks. It has an important role in the estimation of effective anisotropic parameters as well as the incident‐angle‐dependency of P‐ and SV‐wave velocities. Contrarily, randomly distributed cracks with a relative small crack density generally lead to a strong cancellation of stress interactions across cracks, where both the numerical and analytical solutions show a good agreement for the estimation of effective parameters. However, for a higher crack density, the incomplete cancellation of stress interactions is expected, exhibiting an incidence‐angle dependency, slightly affecting effective parameters, and differentiating the numerical and analytical solutions. This article is protected by copyright. All rights reserved

With the increasing pressure, a crack in a medium will be gradually closed, which is affected by stress interactions. The closing process of parallel cracks under vertical stress is simulated here. The coplanar and stacked cracked models are constructed to analyze the influence of two types of stress interaction on the closing process. The spatial distribution of cracks, demonstrated by numerical experiments, has a significant impact on stress interactions and thus the process of crack closure. The mechanisms underlying the delay of crack closure caused by stress interactions are different for the two models. Furthermore, according to the stress dependence of crack microscopic parameters (crack porosity, aperture, and length of major axis), the process of crack closure can be divided into three stages: the linear deformation stage, the contact stage, and the closure stage. In the first stage, no contact is permitted inside the crack. The shielding effect directly leads to a closure lag, and thus a linear stress dependence of the microscopic crack parameter. In the second stage, the shielding effect determines the increasing rate for the stress dependence of microscopic crack parameters in regularly distributed cracked models. However, for the randomly distributed cracked model, local stress interactions result in the eccentric closure of cracks, and thus the crack closure lag. In the last stage, the crack is closed and stress interactions disappear both in the regularly and randomly distributed models.