WANUEL, CHRISTOPHER D., Curtin University of Technology, Dept. of Exploration Geophysics, Perth, Western Australia

ABSTRACT: Attenuation of Seismic Multiples Via Prestack Kirchhoff Depth Migration

Prestack depth migration is the process whereby seismic records in the shot domain are mapped to the spatial domain. This form of inversion is the reconstruction of the causative structures giving rise to the seismic field data recorded. Seismic multiples occur when waves undergo reverberation in the subsurface. Often of high amplitude, these events frequently mask the primary event which are the prime source of information from which subsurface structural information is derived. The occurrence of multiple events on seismic records obtained in the vicinity of Western Australia's North West Shelf is regarded as the greatest impediment to oil and gas exploration in that region.

Most multiple attenuation techniques consider the multiple energy as noise which seismic data processing attempts to eliminate. Hence most processing sequences are only using a portion of the acquired data to image the subsurface with the rest being discarded. By considering the multiple energy to be signal rather than noise, more information may be used in the processing, sequence thus resulting in a more accurate and clearer image of the subsurface. A way to do this is via prestack depth migration. The essence of the technique involves multiple amplitudes being, constructively added to primary amplitudes in order to increase the primary to multiple ratio in the final depth section. Due to this constructive amplitude addition, the resultant multiple reflection amplitudes will be negligible compared with the primary amplitudes. Preliminary testing on simple synthetic datasets has shown a significant multiple reduction in the depth migrated section.

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid