So-called “wave equation” prestack depth imaging techniques have demonstrated value over time migration and Kirchhoff-type prestack depth migration techniques in many basins, such as under salt in the Gulf of Mexico. On land, however, wave equation imaging has a spottier track record. A combination of decreased signal-to-noise ratio, near surface heterogeneity, and non-flat topography make velocity analysis difficult, which in turn limits the general applicability of depth migration. However, we feel that all is not lost--we argue that the right combination of wave equation imaging tools has the potential to provide an edge in land seismic processing. We present a wave equation migration-based velocity analysis scheme which uses depth focusing, rather than residual curvature on an image gather, as a velocity correctness criterion. We feel that our method has some crucial advantages over ray-based reflection tomography algorithms. We go on to show how 3D prestack Shot Record migration can be a surprisingly cost-effective solution for the survey geometries and prospect depths common in many land basins, even in the presence of surface topography, and even in the VSP configuration. We can use our code to provide subsurface illumination attributes, which are superior to surface fold normalization or ray-based “hit count” techniques. We conclude by showing how 3D acoustic wave equation modeling from topography can considerably aid the survey designer in the planning of expensive 3D surveys and also aid the seismic interpreter's ability to better understand the recorded wavefield.
AAPG Search and Discovery Article #90076©2008 AAPG Pacific Section, Bakersfield, California