RELATING P-WAVE ATTENUATION TO PERMEABILITY

To relate P-wave attenuation to permeability, we examine a three-dimensional (3-D) theoretical model of a cylindrical pore filled with viscous fluid and embedded in an infinite isotropic elastic medium. We calculate both attenuation and permeability as functions of the direction of wave propagation. Attenuation estimates are based on the squirt flow mechanism; permeability is calculated using the Kozeny-Carman relation. We find that in the case when a plane P-wave propagates perpendicular to the pore orientation (Q(delta)=90-degrees-1), attenuation is always higher than when a wave propagates parallel to this orientation (Q(delta=0-degrees)-1). The ratio of these two attenuation values Q(delta=90-degrees)-1/Q(delta=0-degrees)-1 increases with an increasing pore radius and decreasing frequency and saturation. By changing permeability, varying the radius of the pore, we find that the permeability-attenuation relation is characterized by a peak that shifts toward lower permeabilities as frequency decreases. Therefore, the attenuation of a low-frequency wave decreases with increasing permeability. We observe a similar trend on relations between attenuation and permeability experimentally obtained on sandstone samples.