We present a case study of anisotropic model building and the resulting accuracy of event placement and improved image quality. Approximately 660 OCS blocks of the MC Revival survey located in Mississippi Canyon area were imaged using anisotropic Kirchhoff pre-stack depth migration (Figure 1). The goals of this large scale project were accurate event placement and improved imaging of steep dips, salt boundaries, and subsalt events. To accomplish these goals, all available well information was used to calibrate the seismic velocity model from prior isotropic pre-stack WEM imaging. The resulting vertical velocity model was used to generate isotropic PSDM image gathers for use in determination of the anisotropy parameters epsilon and delta. These fields were derived from an automated two-parameter residual curvature analysis. Multiple iterations of migration for picking salt overhangs were a necessity to properly image salt bases and subsalt events. Focusing of events was enhanced through iterations of tomography both supra and subsalt. We achieved significant improvements in defining the salt boundaries and in positioning the reflectors and salt overhangs by properly accounting for the effect of anisotropy.

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The Hoop Fault complex in the Southwestern Barents Sea presents an imaging challenge to accurately model the sharp velocity contrast across a major fault boundary. Improperly accounting for this velocity discontinuity would lead a poorly focused image and false structures. We present an approach that leverages interpreted fault planes as well as marker horizons to drive and constrain tomographic velocity updates.

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