Observation and modeling of anisotropic attenuation in VSP data

We analyze a range of VSP datasets for evidence of fracture related attenuation anisotropy, focusing on three attributes: P-wave attenuation anisotropy, differential shear-wave attenuation and frequency dependent shear-wave splitting. We find examples of all three phenomena and are able to reproduce the behaviour with well constrained, unified, theoretical models. Our results suggest a correlation between attenuation anisotropy and fracture properties. It is apparent that in all cases the reservoir displays much higher attenuation than the overburden. Measuring relative attenuation appears to be more robust than measuring absolute attenuation.