Abstract

Subsalt imaging has proven challenging in part because of the complex geometries of the salt canopies, which can yield highly variable illumination on subsalt reflectors. The resulting complexity of the seismic wavefields has also challenged traditional velocity-model-building tools and migration algorithms. A case study for the K2 field illustrates how improved seismic data in the form of long-offset, full-azimuth acquisition and more advanced model building and imaging tools have substantially enhanced the imaging quality of this major subsalt field. The higher fold and more complete azimuthal coverage afforded by the full-azimuth coil data improved the effectiveness of the combined tomographic and full-waveform inversion approach for velocity-model building. Utilization of TTI RTM migration algorithms provided further benefits not only for better delineation of the salt geometry during model building but also in delivering superior final image volumes relative to that which could be provided by less robust algorithms, such as Kirchhoff, beam, and one-way wave equation.

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