Abstract of the paper ``Elastic wave attenuation in rocks containing fluids''
The low frequency limit of Biot's theory of fluid-saturated porous media
predicts that the coefficients for viscous attenuation of
shear waves and of the fast compressional wave are
proportional to the fluid permeability. Although the observed attenuation
is generally in qualitative agreement with the theory, the magnitude of the
observed attenuation coefficient in rocks is often more than an order of
magnitude higher than expected. This apparent dilemma can be resolved without
invoking other attenuation mechanisms if the intrinsic permeability of the
rock is inhomogeneous and varies widely in magnitude. A simple calculation
of the overall behavior of a layered porous material using local-flow Biot
theory shows that the effective permeability for attenuation is the
mean of the constituent permeabilities while the effective permeability for
fluid flow is the harmonic mean. When the range of variation in
the local permeability is one or more orders of magnitude, this difference
in averaging method can easily explain some of the observed discrepancies.
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