Azimuthal anisotropy? The time and depth imaging points of view: an imaging case history

The superior imaging capabilities of wide azimuth (WAZ) are now well established. Processing such acquisitions rquires adaptation of the processing workflows and tools. For example the recorded azimuthal information must be kept and the tools should be able to deal with the increased amount of data. Concerning the velocity model building, a question remains on the need of introducing azimuthal anisotropy. In this paper we address this point with a time and depth imaging case study for a high density wide azimuth (WAZ) land surface acquisition. We show on this dataset that azimuthally varying residual move-out observed on time migrated common image gathers (CIG) definitely disappears on the depth migrated CIGs (in both cases no azimuthal anisotropy is introduced in the velocity model). This illustration highlights the limits of the assumptions of time imaging, thuis promoting the use of depth imaging when processing high-density WAZ data, even in the context of mild geological complexity.