Paper Summary

Reverse-time migration (RTM) provides superior images in areas where there are steep salt flanks or other complex geologic structures. However, the high cost of running RTM with regard to memory requirement and computation time makes it difficult to use RTM for routine large volume production. By dividing the subsurface into two or three regions in depth according to the structures of the velocity model and applying RTM from top to bottom sequentially in each region, we are able to make RTM very cost effective for production usage. Further more, Kirchhoff migration or one-way wave equation migration may be used to replace RTM in a region where the velocity model is relatively simple and RTM may not help to generate a better image. This hybrid approach may further improve the computation efficiency and the quality of migration images.