A simple and accurate model for attenuation and dispersion caused by squirt flow in isotropic porous rocks

Seismic waves propagating in fluid-saturated porous rocks exhibit attenuation and velocity dispersion in a broad range of frequencies. At sonic and ultrasonic frequencies, the attenuation is predominantly caused by fluid flow in cracks and grain contacts, so-called squirt flow. This physical mechanism for attenuation may also be relevant at seismic frequencies. We present a simple and accurate analytical model for attenuation and dispersion caused by squirt flow in isotropic porous rocks. The input material properties for a specific rock model can be directly measured in a laboratory or calculated using analytical and numerical approaches. The results from our squirt flow model are compared to inherently accurate three-dimensional numerical solutions for the same pore geometries. The analytical and numerical results are in good agreement. Furthermore, we observe that the proposed analytical model is more accurate than the published analytical solution for squirt flow in isotropic porous rocks. Matlab routines to reproduce the presented results are made available.