Offset Vector Tile Anisotropic Tomography and PreSDM of the Hild OBC

In this work, we have performed model building and 3D PreSDM on P-wave data from a 3D OBC survey using offset vector tile (OVT) processing, wherein the velocity is estimated by a surface fitting non-sectored approach, characterising velocity in terms of a fast and slow direction, along with the azimuth of the fast axis. Using OVT VTI tomographic inversion permits us to thereby better resolve localized heterogeneity that is usually left unresolved when using a conventional non-OVT tomographic approach. In addition to the OVT VTI tomography, we followed the 3D PreSDM model building and migration with an HTI azimuthal velocity analysis in an attempt to characterize any dominant fracture patters: in this case, no dominant patterns were found. We compare the results with existing data showing how rigorous handling of azimuths better constrains the lateral velocity variations and results in a better focused image in the Jurassic, especially of steep fault planes.