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