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GeoTomo
810 HWY 6 S STE 220
Houston, TX 77079
Tel: 281-597-1429
Fax: 281-597-1201
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| VELMAP Release
Version 2.0 |
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VELMAP New Features
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This release is made on June 28, 2004 |
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Improved automatic
first-break picker: The automatic first-break picker
has been modified for working with VSP data. This is a picking
technique that combines geometry projection, single-trace
amplitude variations, and correlations among traces. With this
technique the user can quickly move from shot to shot generating
reliable first-breaks. You can pick either in common-shot or in
common-receiver gathers. |
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Preprocessing including F-K wavefield separation: VELMAP
provides comprehensive signal processing to prepare SEGY data
for migration. Included are processes for deconvolution, trace
mute, time scaling, time-variant spectral whitening, band-pass
filter, AGC, median filter and F-K wavefield separation. Raw
VSP data can be processed to reduce noise and enhance signal
quality. Using selected shots, the user can interactively
determine the best parameters and processing sequence to
condition the data. Along with the trace display, the Average
Amplitude Spectrum, the Time Variant Amplitude Spectrum, and the
Autocorrelogram of the traces are shown to help you determine
the effectiveness of each process. Once the optimum sequence
is determined, it is then applied to the entire data set. |
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Shot regularization for wave-equation migration:
Wave equation migration requires that the traces be regularly
sampled at the surface. VELMAP makes it easy to regularize any
VSP survey, even if the original shots have irregular spacing.
In the Preprocess module, after applying the other trace
conditioning, the user only needs to specify the initial shot
coordinate and the shot spacing. The traces will automatically
be resampled to match this geometry. |
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Tomography with structure constraints:
Tomography usually generates a velocity model that is somewhat
smooth in depth. However, for VSP tomography, the user may
already have structure knowledge from surface seismic images and
well logs. In these cases, the user can use interpreted
interfaces as a constraint during the tomography. The
tomography solution will not smooth across these interfaces,
creating a sharper velocity contrast. Begin by making an
initial tomographic inversion. Then, using the velocity model
created, interpret one or more geological interfaces on the
model or seismic image in Grid Model. Finally, re-run
the tomography applying the interpretation as a constraint. |
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Interactive update of 2D/3D velocity model for migration:
Velmap allows the user to display the velocity model
used for migration along with the migrated SEGY traces. The
traces will be superimposed over the velocity model. This
allows the User to QC the migration and the velocity model to
see if there is a good match and the results are as expected.
The 2D or 3D velocity model can then be interactively edited,
using the migrated traces as a guide. The new velocity model
can then be used to migrate the survey again. This process can
be repeated several times if necessary to produce an
image-consistent velocity model. |
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