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Abstract: Seismic Indicators for Porous Fluid-Saturated Layer

Gennady M. Goloshubin

Analysis of the wave propagation in a porous layered fluid-saturated media reveals that the seismic response to such media may differ from that of its solid elastic equivalent. Channel slow wave phenomena low resonance frequencies and apparent velocity dispersion are among the significant seismic characteristics of such media.

1. Slow Wave. The differences between propagation in single and multiphase media are remarkable in the case of a thin porous layer. In this case it is found that the channel slow wave phenomenon occurs. That is, the slow wave can propagate at long distances, depending on the fluid content. The slow wave is a direct hydrocarbon indicator.

2. Resonance Frequencies. The seismic resonance characteristics depend on several factors; i.e., thickness of the layer, matrix porosity, permeability and the fluid viscosity. The porous fluid saturated layer always has lower resonance frequency than a solid layer of the same dimensions. Thus, a shift to low resonance frequency of the layer may be an indicator of its fluid saturation.

3. Velocity Dispersion. Velocity analysis of seismic data and physical modelling and corresponding analytical solutions indicate the apparent velocity dispersion of reflected (from thin porous liquid-saturated layer) wave. It is a trace of different reflection peak phase for different frequencies. The apparent velocity dispersion of the reflected wave may be an indicator of liquid-saturated reflector.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela