Geometry QC Package
goal of Geometry QC is to ensure that source and receiver coordinates
are accurate and consistent with the seismic data. This can be performed
in the field or after the survey. If performed in the field, all bad points
should be re-surveyed (when possible). After the survey, the recomputed
coordinates will give an approximation of the actual position. A valuable
product of using SeisNav Resolve for Geometry QC is creation of merged
SEG Y files, i.e. the seismic data is in standard SEG Y format where the
trace headers contain coordinates and elevations from the survey data
as well as computed values such as offset and source/receiver azimuths
and complete binning details. The value in this product is that these
SEG Y files can be input directly into ProMAX and/or other processing
systems for complete processing starting with 3D DMO. Note that some Geometry
QC can be performed without merging the seismic data, however, the total
QC results are far superior when merging is done. Results from all QC
tasks listed below can be displayed in a professional format to depict
problems and/or solutions. Tasks that should be performed include:
coordinates overlaid on a topography map (if applicable, we support
TIFF and GIF image formats and have tools for graphically splicing images
and registering them for the coordinate overlays). Verify the elevations.
Overlays will also show the reasons for many changes to the shot or
receiver layout. The topography maps may be obtained and scanned during
the position surveying, and the first coordinate overlays should be
made with the preshoot survey data.
- At the
preshoot stage, or any other time during the survey, the survey data
may be binned. Examine the offset distribution cube, and generate aerial
slices at different offsets to look for holes in coverage. Skipped surface
locations are accurately imaged at depth. Generate a "TIME VARIANT FOLD"
data volume in SEG Y format. Examination of time slices of fold at important
prospect horizons can be achieved. Evaluate the need of infill shooting.
These displays are generated with a representative velocity function
and a suitable muting scheme.
of coordinates against a preshoot data set. This will highlight gross
coordinate errors as well as missing nav/survey data.
of cable separation along a receiver line. If the cables only have a
small amount of slack, certain separations are physically impossible.
surface displays of the coordinates in separate maps to verify consistency
between source and receiver elevations. Color-coded flat map can also
be used for this comparison. Many times in land or OBC jobs, the sources
and receivers are surveyed separately. Thus, near receiver and source
positions should be consistent in all three directions (x,y,z).
survey data and binning information into trace headers of seismic data.
This step is for checking and resolving Observer Log discrepancies and
survey data problems. View traces with a computed first break time (based
on computed offset, a near surface or water velocity and a system delay
time) overlaid. This should be performed for both shots and receivers
separately. This merge data can be saved to tape to provide a head start
the merge in the "Shooting Nav" or "2D Edit" display to see geometry
and seismic on the same screen. These are good tools for visualizing
how the seismic traces reflect bad geometry. LMO (linear move-out) may
be performed inline with the "2D Edit" display for viewing as "flat
coordinates (in batch mode with the Residual Nav processor or interactively
with Geometry Workshop) for any points (sources or receivers) which
seem bad. This recompute should be verified against the seismic to ensure
improvement. In the "Geometry Workshop" display, the user can interactively
pick first breaks and recompute coordinates and see the adjusted computed
first breaks based on the new coordinates.
a near-trace cube to verify coordinate consistency.
a brute stack to further verify coordinate consistency. A brute stack
should be performed before and after applying recomputed coordinates
to the data to make sure there is improvement. This process also generates
time variant fold or time variant average offset, which may be displayed
separately or overlaid on the seismic.
Binning QC Package
provided in SeisNav Resolve can be used before or during production to
analyze a survey. When a survey is being designed, users will get binning
and coverage analysis to help achieve the desired offset and azimuth results.
During shooting, the software can show the effects of moved shots and
receivers on coverage. Binning features include;
and analysis is provided by the Binning module. This provides
the following binning features for nav data without regard to the seismic:
Computes a redundant and non-redundant fold for each bin. These
show coverage of the survey area.
a series of folds inside each bin according to a distribution key.
This can be used to compute an offset-variant fold to view coverage
at all offset levels. Azimuths could also be analyzed to see
the coverage in different azimuth ranges.
the minimum, maximum, or average value of any attribute inside each
bin according to a distribution key. In the above example, instead
of offset-variant fold, create an offset-variant average azimuth.
the time-variant fold that should be provided by this data given
a velocity function and muting scheme.
a merge of the seismic data and navigation coordinates, binning is performed.
The CDP, inline, and crossline numbers are computed. Binning attributes
computed are CDP deviation, source/receiver azimuth, and offset. The
x and y coordinates of the center of the bin is also stored in the header.
Binning Displays are devoted to displaying the output of
the Binning module. This display draws one box for each
bin in the display. Inside this box can be a histogram or a spider plot
based on the SEG Y data output from the Binning module. The histogram
should be used to view a histogram of information pertaining to the
bin. For instance, if you run an OFFSET header stack, the picture will
tell you the total number of traces in this bin at each of your specified
offset ranges. The spider plot could be used to look at min/max/average
source/receiver azimuth within the bin.
the binning information using other SeisNav Resolve displays is quite
simple and useful. The information produced by the Binning
module will read directly into any of the displays. Fold maps can be
created as a 2D flat map, 3D surface, 3D histogram, or even overlaid
on a topography map to see physical reasons for coverage changes.
compression of large P1/84 and P1/90 navigation files is available to
assist in reducing system requirements. Typical compression ratios are
50:1 to 60:1. The other attraction to our compression is that our Binning
module can read and process the compressed files.
- A number
of survey file utilities for comparing and manipulating SEG P1 and SPS
files are also available.
3D Velocity QC Package
QC provided in SeisNav Resolve can be used during production velocity
picking/analysis or after to build cubes for analyzing velocities over
a entire survey. Additionally, inputting velocities used to process data
from 2D surveys in the area and building a velocity cube, can be useful
in the design phase of a 3D survey as well as giving a good start on brute
stack velocities for in field processing. Velocity QC features include;
of various ASCII T/V pairs file formats, e.g. Tensor, ProMAX, Geco,
, linearly interpolating in time and in space for the
control point key, and outputting a SEG Y format file with the trace
data containing the velocity functions. At the same time as T/V pair
input, a matching horizon file with up to 8 horizons may be input and
output in the SEG Y trace headers. The trace interpolation processor
will allow linear interpolation between pairs of control points in either
the crossline or inline directions for filling in the velocity volume.
Option processing would include;
RMS velocities to interval or average velocities with the velocity
the velocities using the iterative filter processor.
Velocity Edit Display gives viewing and editing capability of the control
points defining a 2D velocity field. The display also shows both RMS
and interval velocities as well as overlaying horizons from a file or
the trace headers. ASCII T/V pairs files may be input directly into
this display, and editing may be saved to another file.
Profile Display allows multiple views of the velocity data as a two
dimensional graph, a three dimensional histogram, or a three dimensional
2D Display supports viewing 2D velocity fields in a color display. It
also allows for viewing seismic data with a color coded velocity field
underlaid and/or multiple horizons overlaid.
- A velocity
volume may best be examined for consistency in all directions using
the Cube Display. An interesting feature of this display is a 3D animation
through one or more velocity isosurfaces.
the velocity data is output as SEG Y, the files may easily be input
into other seismic processing software packages for processing or display.