Time-to-depth conversion and seismic velocity estimation using time-migration velocity

Conclusions

We have applied the recently established theorem that the Dix velocity obtainable from the time-migration velocity is the true interval velocity divided by the geometrical spreading of image rays to pose the corresponding inverse problem. We have suggested a set of numerical algorithms for solving the problem numerically. We have tested these algorithms on a synthetic data example with laterally heterogeneous velocity and demonstrated that they produce significantly better results than simple Dix inversion followed by time-to-depth conversion. Moreover, the Dix velocity may qualitatively differ from the output velocity. We have also tested our algorithm on a field data example and validated it by comparing prestack time migration image mapped to depth with post-stack depth migrated images. Our approach is complementary to velocity estimation methods that work directly in the depth domain. Therefore, it can serve as an efficient first step in seismic velocity model building.