Comparative Analysis of Kirchhoff and Beam Pre-Stack Depth Migration for OML (XYZ) Field Offshore Niger Delta

Abstract

3D Seismic data were analyzed for comparisons between unmigrated and migrated seismic section. Kirchhoff and Beam Pre-stack depth migration are two methods used in seismic data processing, a step which focuses events by repositioning dipping reflections into their correct location and collapse diffractions into a point as hydrocarbon reservoir traps could be an anticline, termination of dipping layers at a fault or unconformity. Seismic data were acquired from OML (XYZ) field in Niger Delta and processed for correction of dipping events for proper imaging of subsurface structures. Depth migrationutilizes the assumption that correct velocity model produces flat migrated gathers. Therefore, a velocity model was built and the images obtained after two iterations were used for the final migrationusing Kirchhoff Pre-stack depth and Beam Pre-stack depth methods for comparisons. In area of complex geologic formation, the images of KPreSDM were fragmented and migration artifacts were seen whereas Beam migrated gathers shows continuity for proper identification of faults, folds and diapers. Kirchhoff images had true amplitude which can be used for AVO studies while Beam PreSDM enhances the amplitude seen on the seismic section and this is not good for AVO studies, though could be useful to view the reflectors if they are flat or not. Beam migration is good because they are not easily attenuated.Its ability to penetrate deeper into the subsurface guaranteed it usefulness for Seismic inversion analysis.