Seismic attenuation in partially saturated fractured aquifers

A conceptually simple superposition model is presented for dispersion and attenuation of compressional waves in fractured porous rocks that are saturated by a mixture of two pore fluids. These two different types of heterogeneities are described by four parameters: The fracture spacing (fracture density) and fracture weakness characterizing the fractured medium; the correlation length and degree of saturation characterizing the fluid patches that are embedded between the fractures. This model is employed to explain the relatively strong P-wave velocity dispersion found for a limestone reservoir. We conclude that the mechanism of wave-induced flow may well explain large P-wave dispersion and attenuation in heterogeneous porous media.