Elastodynamic Redatumming for VSP Salt Dome Flank Imaging
Author(s)
Lu, Rongrong; Willis, Mark E.; Campman, Xander; Toksoz, M. Nafi
Download._Lu_elastic_ERL2007.pdf (82bytes)
Other Contributors
Massachusetts Institute of Technology. Earth Resources Laboratory
Metadata
Show full item recordAbstract
In this paper we construct an application methodology for the theoretical elastodynamic
redatumming work by Wapenaar (2006) to be able to approximate its use in the problem of
imaging a salt dome flank using a walk away VSP (WVSP). Different from acoustic redatumming
where only one quantity, the pressure, is involved, full elastodynamic redatumming requires both
P-wave source and S-wave sources with different polarizations. We approximate these P-wave and
S-wave sources by implementing a shooting pattern for each shot position of an ordinary WVSP
acquisition. We create a synthetic WVSP dataset with modified shooting pattern for a model
composed of a simplified Gulf of Mexico vertical-velocity gradient, an embedded overhanging
salt dome together with a nearby salt canopy. To process these data, we first compile the raw
dataset due to the shooting pattern into a new dataset which approximates common receiver
gathers due to P-wave source and S-wave sources, respectively. We then apply elastodynamic
redatumming to this new dataset to mimic the response between different components for
downhole source and receiver pairs. The reconstructed traces show a good match to the traces in
the benchmark case, which we create by firing actual downhole sources and recording the
responses at all downhole receivers. Instead of a more proper, full elastic migration, we apply
simple acoustic migration on individual components of the full elastic Green’s functions to
produce pre-stack depth migrated images of the salt dome flank and the dipping sediments. By
performing four migrations of these components, we obtain very good separate images of the
subsurface using predominately either P or S wave energy. The horizontal sediments and vertical
salt flank decouple and appear on separate images.
Date issued
2007Publisher
Massachusetts Institute of Technology. Earth Resources Laboratory
Series/Report no.
Earth Resources Laboratory Industry Consortia Annual Report;2007-15