A Rock Physics Model for Fractured and Patchy-saturated Reservoirs

A rock physics model is presented for dispersion and attenuation of compressional waves in fractured porous rocks that are saturated by a mixture of liquid and gas. These two different types of heterogeneities are described by four parameters: The fracture spacing 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 extremely strong P-wave velocity dispersion in a narrow frequency range found for a limestone reservoir. The results indicate that seismic attenuation and dispersion may provide additional constraints on relevant reservoir parameters.