Effect of stress interactions on anisotropic P-SV-wave dispersion and attenuation for closely spaced cracks in saturated porous media |
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| Authors: | Chenghao Cao Fangyuan Chen Li-Yun Fu Jing Ba Tongcheng Han |
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| Institution: | 1. School of Transportation Engineering, Nanjing Tech University, Nanjing, 210009 China;2. Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Shandong, 266580 China;3. School of Earth Sciences and Engineering, Hohai University, Nanjing, 211100 China |
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| Abstract: | Generally, local stress induced by individual crack hardly disturbs their neighbours 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. |
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| Keywords: | Anisotropic parameter Attenuation Dispersion Rock physics Velocity analysis |
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