Slowness surface construction and inversion from 3D VSP data

The emerging technology of three-dimensional vertical seismic profiles (3D VSPs) allows the extensive sampling of reflecting surfaces over a wide range of incident angles and azimuths. Such data can be used to provide additional insights into the effective rock properties associated with features that are below seismic resolution, such as layering or aligned systems of fractures which lead to elastic anisotropy. Here we analyse two 3D VSPs acquired in the Arabian Gulf and show how the data may be processed to extract slowness surfaces, how these surfaces can be used to estimate anisotropy parameters, and how the anisotropy relates to the geological characteristics of the formation and its stress history.