Eliminating 3D pre-stack migration artefacts by 6D filtering

摘要

State-of-the-art 3D seismic acquisition geometries have poor sampling along at least one dimension. This results in coherent migration noise that always contaminates pre-stack migrated data, including high-fold surveys, if prior-to-migration interpolation was not applied. We present a method for effective noise suppression in migrated gathers, competing with data interpolation before pre-stack migration. The proposed technique is based on a dip decomposition of common-offset volumes and a semblance-type measure computation via offset for all constant-dip gathers. Thus the processing engages six dimensions: offset, inline, crossline, depth, inline dip, and crossline dip. To reduce computational costs, we apply a two-pass (4D in each pass) noise suppression: inline processing and then crossline processing (or vice versa). Synthetic and real-data examples verify that the technique preserves signal amplitudes, including amplitude-versus-offset dependence, and that faults are not smeared.