In 2009, BP initiated a complete reprocessing of the Mad Dog WATS (wide-azimuth towed-streamer) dataset using TTI (tilted transverse isotropy) Pre-stack Depth Migration (PSDM) technology developed by CGGVeritas. This project would build upon the 2008 VTI (vertical transverse isotropy) model built by CGGVeritas by improving key areas that were imaged poorly. The TTI reprocessing was extremely successful. In fact, the uplift for the subsalt target area was qualitatively larger than the uplift

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... than the uplift observed between isotropic and VTI. Mad Dog TTI reprocessing further confirmed that by honoring the stratigraphic layering of the geologic structure, a TTI velocity model is a better approximation of the subsurface than both isotropic and VTI models. The Mad Dog WATS data combined with a previously recorded NATS (narrow azimuth towed streamer) dataset allowed the ability to detect and account for anisotropy in different azimuths, which is not possible with a single NATS survey. TTI reverse time migration (RTM) improved the ability to define salt geometry and thereby obtain a good subsalt image. TTI RTM should be considered for future imaging of fields with complex structures such as Mad Dog.