Imaging Using Multi-arrivals: Gaussian Beams Or Multi-arrival Kirchhoff?

Single-arrival Kirchhoff migration is an accurate and reliable depth migration method except in cases of extreme geologic complexity, where it is not as accurate as most wavefield continuation methods. Also, where geology is extremely complex and multipathing occurs, its reliance on migrated image gathers indexed by offset (while more convenient than image gathers indexed by shot number) causes problems for both amplitude analysis and velocity analysis. On the other hand, most wavefield continuation methods are relatively expensive, and problems with amplitudes and migrated image gathers remain. Multiarrival Kirchhoff migration can, to a large degree, overcome the problems associated with both single-arrival Kirchhoff and wavefield continuation methods, but the data flow problems can be serious in a production environment. Gaussian beams can be used to provide accurate Green’s functions for multi-arrival Kirchhoff migration, and in the limiting case, kinematically accurate Gaussian beam migration can be modified to provide accurate amplitudes and migrated gathers indexed by angle.