Wave-equation time migration

Conclusions

The proposed seismic imaging workflow is applicable to areas with mild lateral velocity variations. Mild variations are required to ensure that image rays do not cross, so that the mapping between image-ray coordinates and Cartesian coordinates remains one-to-one. We have outlined a theoretical foundation for the central step of this workflow (wave-equation time migration) and demonstrated its application using synthetic and field data examples. Wave-equation time migration produces an image in time-migration (image-ray) coordinates but without using moveout approximations or any other limitations associated with traditional prestack-time-migration algorithms. The proposed algorithm can be cost effective because it circumvents the need for multiple migrations that are required to update the velocity model in depth for the conventional algorithms during the velocity model building process. In complex velocity models, when the image-ray coordinate system breaks down because of crossing rays, the proposed workflow may not be directly applicable. However, it can be combined with redatuming (downward extrapolation) to allow the velocity model to be recursively estimated below the depth of the break-down point. The proposed algorithm can also be extended to prestack domain which is a subject for future research.

Wave-equation time migration