Dispersion and attenuation of P-waves in porous rocks with aligned fractures

Abstract

Fractures in a porous rock can be modeled as very thin and highly porous layers in a porous background. Elastic moduli of a porous rock permeated by a system of such fractures distributed periodically can be obtained using the result of Norris (1993) for elastic properties of layered poroelastic media. When both pores and fractures are dry, such material is equivalent to a transversely isotropic dry elastic porous material with linear-slip interfaces. When saturated with a liquid this material exhibits significant attenuation and velocity dispersion due to wave induced fluid flow between pores and fractures. The characteristic frequency of the attenuation and dispersion depends on the background permeability, fluid viscosity, as well as fracture density and spacing.