[1] The attenuation effects predicted by Hickey's poroelastic theory (Hpt) are quantified by means of seismic modeling in an unbounded, homogeneous, isotropic porous model fully saturated with water and with oil. The numerical results are compared to those predicted by Biot poroelastic theory (Bpt). As opposed to Bpt, Hpt accounts for thermomechanical coupling and viscous fluid relaxation and adequately models the transient fluctuations of porosity and mass densities as the wave compresses and dilates the porous medium during propagation. Despite all these theoretical improvements over Bpt, the numerical results show that both theories produce remarkably similar waveforms. Without considering thermal relaxation, Hpt produces less than 1% higher-amplitude attenuation and velocity dispersion than Bpt. The major contrasts correspond to the slow P wave. Thermomechanical coupling affects the fast P wave: seismic amplitudes are 1% smaller and some dispersion for the oil-permeated case can be observed. It produces no effects on the fast S or the slow P wave. Therefore these numerical experiments appear to substantiate what Biot assumed at the outset of his theoretical developments: that the effects of transient oscillations of porosity during wave propagation are negligible in terms of velocity dispersion and amplitude attenuation. Furthermore it is confirmed that in a homogeneous porous medium, the combined dissipation mechanisms mentioned are not adequate to explain the total amount of energy dissipation observed in the field or laboratory.Citation: Quiroga-Goode, G., S. Jiménez-Hernández, M. A. Pérez-Flores, and R. Padilla-Hernández (2005), Computational study of seismic waves in homogeneous dynamic-porosity media with thermal and fluid relaxation: Gauging Biot theory,
S U M M A R YIt is quantified the properties of seismic waves in fully saturated homogeneous porous media within the framework of Sahay's modified and reformulated poroelastic theory. The computational results comprise amplitude attenuation, velocity dispersion and seismic waveforms. They show that the behaviour of all four waves modelled as a function of offset, frequency, porosity, fluid viscosity and source bandwidth depicts realistic dissipation within the sonicultrasonic band. Therefore, it appears that there is no need to include material heterogeneity to model attenuation. By inference it is concluded that the fluid viscosity effects may be enhanced by dynamic porosity.
[1] The polarization of body waves in a fluid-saturated homogeneous porous sandstone is quantified by computing the Green's function; the findings are confirmed with grid modeling. Both results agree that forces in an unbounded homogeneous isotropic porous medium generate harmonic perturbations whose particle motion varies along the wavefront from linear to elliptical; such behavior typically associated to homogeneous and inhomogeneous viscoelastic plane waves in layered media. Following this analogy, it is concluded that the attenuation angle g is the function of the direction of wave propagation, wave type, and direction of the applied force. With this information, the attenuation angle g 1 of the initial ray segment can be estimated, resolving in a different manner the issue of indeterminacy in the asymptotic ray solution. It is also concluded that the assumption of g 1 = 0 for normally incident viscoelastic plane waves in layered media may be correct, but only for P waves generated by vertical forces; as propagation direction increases, so does the error, the rate depending on Q. The results also show that (1) a P wave resembles a S wave and vice versa for preferred directions and (2) the sense of particle motion is opposite for both waves, prograde and retrograde, respectively, and vice versa, depending on the direction of the applied force.Citation: Quiroga-Goode, G., S. Jiménez-Hernández, and R. Padilla-Hernández (2009), Numerical evidence of elliptical polarization in homogeneous fluid-saturated porous sandstone and the nexus to inhomogeneous plane waves,
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