Seismic attenuation in porous layered fluid-saturated medium

This work evaluates attenuation effects on wave propagation in a Biot medium at seismic frequencies (0--100Hz) using asymptotic analysis. The modeling results confirm that the asymptotic solution corresponds to the exact Biot solution at seismic frequencies and shows significant frequency-dependant losses of P-wave energy at permeable boundaries. Calculation of attenuation in a thin-layered permeable reservoir model reveals unimodal behavior of P-wave attenuation versus frequency with highest attenuation (Q=22) at 40Hz. This attenuation is at least 2 orders of magnitude higher than that of a uniform homogeneous reservoir model. Attenuation influences reflective properties of the reservoir through Fast P-wave and converted Fast-Slow-Fast P-wave reflections. Due to high Slow P-wave attenuation, the converted waves may play a noticeable role in the forming of reflected waves at seismic frequencies only at small dimensions of heterogeneities (layer thicknesses less than 1 m). Otherwise, the converted Fast-Slow-Fast P-waves effect is less than the multiple reflections effect.