Overview

Prestack Stolt residual migration can be applied to seismic images that are depth migrated using wavefield extrapolation techniques. Residual migration allows us to estimate velocity inaccuracy not only by measuring flatness of angle-domain common image gathers, but also by measuring focusing along the spatial axes. Therefore, residual migration is useful in conjunction with a migration velocity analysis tool capable of using such information for velocity updates.

Residual migration can be implemented efficiently in the frequency-wavenumber domain as a function of a scalar parameter relating the background velocity to a trial velocity. Although the theory is developed assuming constant velocity, the method can be used for depth-migrated images produced with smoothly varying velocity models, since the residually migrated images depend only on the ratio of the reference and updated velocities. This method closely resembles Stolt-stretch techniques, and so it inherits Stolt's method speed and convenience. The main applications of this method are in migration velocity analysis (MVA) where it can be used to investigate the effects of gross velocity changes on the migrated image, and as a tool for residual image enhancement employed by more sophisticated MVA methods, for example by wave-equation migration velocity analysis wemva.