NAME
cdpstk3d - marine or quickie NMO and CDP stack
SYNOPSIS
cdpstk3d [ -Nntap ] [ -Ootap ] [ -vvtap ] [ -tdfn ] [ -mmtap
] [ -wwind ] [ -sscale ] [ [ -dmindstmin ] [ -dmaxdstmax ] [
-angmxangmax ] [ -angmnangmin ] [ -diminmindi ] [ -dimax-
maxdi ] [ -liminminli ] [ -limaxmaxli ] ] [ -x1x1 ] [ -y1y1
] [ -x2x2 ] [ -y2y2 ] [ -x3x3 ] [ -y3y3 ] [ -x4x4 ] [ -y4y4
] [ -cldmcldm ] [ -ildmildm ] [ -R ] [ -nmoap ] [ [ -norm ]
[ -Tttap ] [ -dexpdexp ] ] [ -V ] [ -? ]
DESCRIPTION
cdpstk3d is a simple NMO correction (with optional distance
mute) and CDP bin stack designed for either marine data or
for a quickie tape-to-stack run. Currently just a plain
vanilla NMO (quadratic interpolation) is made to the data
before stacking. Provision is made for distance limiting
the stack and also for rejecting azimuth ranges.
The input data can be in any sort order (shot, group, cdp,
offset) but must at least have the source X-Ys (SrPtXC and
SrPtYC) and the receiver X-Ys (RcPtXC and RcPtYC) trace
header words properly filled in since these are are critical
to calculating where the trace belongs.
For data in shot order it is assumed that the basic correc-
tions have been made, e.g. refraction statics, velocity
analysis, residual statics. Other processes such as deconvo-
lution and coherent noise filtering can be done on the fly
before input into the cdp bin stack.
cdpstk3d gets both its data and its parameters from command
line arguments. These arguments specify the input, output,
the cdp velocity, output survey extent, optional range and
azimuth reject limits, and verbose printout, if desired.
Command line arguments
-N ntap
Enter the input data set name or file immediately after
typing -N unless the input is from a pipe in which case
the -N entry must be omitted. This input file should
include the complete path name if the file resides in a
different directory. Example -N/b/vsp/dummy tells the
program to look for file 'dummy' in directory '/b/vsp'.
-O otap
Enter the output cdp stack data set name or file
immediately after typing -O. This output file must be
a disk file and cannot be piped.
-v vtap
Enter the name of the RMS velocity disk file. There are
two options: (1) a single tdfn function can be speci-
fied (-tdfn must be flagged on the command line in this
case); (2) an entire velocity field with one velocity
tape-format function per bin location (the bins must
correspond to the output cdp stack bins). In option (2)
the there must be a velocity function at every bin
location but the function can be coarsely sampled in
time (e.g. every 100ms). The cdp program will automati-
cally resample the coarse function using a cubic spline
interpolator. Also for option (2) the velocity file
must be on disk since the program does random access
seeks to extract the correct velocity (in the case of a
multiple function velocity file).
-m mtap
Enter (optional) the name of the file containing a
distance-time mute function which will be applied after
NMO correction. The format is similar to that for a
velocity flat file: each line consists of a time (ms),
an offset (ft,m), and a record number. The function is
terminated by a negative time (followed by any two
values). Currently only a single function is allowed so
you can put any record number in the third column (but
you must put something). There is also a default ramp
of 48ms applied starting at zero 48ms earlier then the
given mute time and ramping to one at the mute time. If
an input trace offset lies outside the mute function
distance range no muting is done. Default is to do no
muting at all if the -m[] is left off the command line.
x4, y4]
-x1, -y1, -x2, -y2, -x3, -y3, -x4, -
y4 [x1, y1, x2, y2, x3, y3,
Enter the area of interest over the survey with the X-Y
coordinates (ft,m) defining the four corners of a
parallelogram on the ground. Going either clockwise or
counter clockwise (clockwise recommended) from Corner 1
the first move to Corner 2 should be in the direction
of a receiver or shot line. The direction 1-2 will
always define the Y or DI direction. The DIs will
always start from side 1-4 and increase in the 1-2 (Y)
direction; the LIs will always start from side 1-2 and
increase in the 1-4 (X) direction. The values must be
the same units as those given in the source, receiver,
and midpoint X-Ys in the trace headers.
-cldm cldm
Enter the crossline (along X or side 2-3) cell dimen-
sion (ft,m). For most shooting geometries this will be
1/2 the line or group spacing depending on the
orientation of side 2-3 with respect to the receiver
lines. The sides are defined to be X along side 1-4
(roughly cross-line direction), Y along side 1-2
(roughly in-line direction). Remember when setting up
the coordinate system the line joining Corner (1) to
Corner (2) should be in the direction of a receiver or
shot line. No default.
-ildm ildm
Enter the inline (along Y or side 1-2) cell dimension
(ft,m). For most recording geometries this will be 1/2
the line or group spacing depending on the orientation
of side 1-2 with respect to the receiver lines. The
sides are defined to be X along side 1-4 (roughly
cross-line direction), Y along side 1-2 (roughly in-
line direction). Remember when setting up the coordi-
nate system the line joining Corner (1) to Corner (2)
should be in the direction of a receiver or shot line.
No default.
-dmin dstmin
Enter the minimum offset to use in the cdp (in ft,m).
Default is to use the smallest offset.
-dmax dstmax
Enter the maximum offset to use in the cdp (in ft,m).
Default is to use the largest offset.
-limin, limax minli, maxli
Enter the minimum and maximum line indexes to output.
The output survey will have so many bins in the inline
direction and so many bins in the crossline direction.
This is a handy way to start and end outputting bins at
specified sequential inline numbers. Default is the
first and last inline bin as determined from the 4
corners of the survey provided on the command line..
-dimin, dimax mindi, maxdi
Enter the minimum and maximum crossline indexes to out-
put. The output survey will have so many bins in the
inline direction and so many bins in the crossline
direction. This is a handy way to start and end output-
ting bins at specified sequential crossline numbers.
Default is the first and last crossline bin as deter-
mined from the 4 corners of the survey provided on the
command line..
-angmx angmax
Enter maximum azimuth to reject (degr). If the minmum
and maximum reject angles are equal no azimuthal rejec-
tion will be done. Default = 0
-angmn angmin
Enter minimum azimuth to reject (degr). If the minmum
and maximum reject angles are equal no azimuthal rejec-
tion will be done. Default = 0
-w wind
Enter the AGC scaling window in ms. Default = 0, i.e.
no AGC
-s scale
Enter the AGC scaler in % 2047. Default = 15%
-R Enter the command line argument '-R' to restart a pre-
vious run that has stopped for some reason. The stderr
messages will announce every sequential record about to
be processed so the user can easily determine where in
the input data set the process stopped. By using suit-
able editt parameters the cdp run can be continued at
the point at which it stopped without the previous data
being wiped.
-nmoap
Enter the command line argument '-nmoap' if NMO has
already been applied to the input data.
-norm
Enter the command line argument '-norm' to turn on the
normalization option. This will cause another output
file to appear, equal in size to the stack output,
which is used to keep track of the number of live sam-
ples summed into any given trace at every time sample.
-T ttap
Enter the name of the disk file containing the normali-
zation data. This will be about the same size as the
output stack data set. This output cannot be piped.
-dexp dexp
Enter the exponent for the normaization operation. Each
output cdp stack sample will be divided by the number
of live samples that created that stack sample raised
to the dexp power. Default = 1.0
-V Enter the command line argument '-V' to get additional
printout.
-? Enter the command line argument '-?' to get online
help. The program terminates after the help screen is
printed.
BUGS
No checks on the input trace headers to see if they have
valid source, receiver, or midpoint X-Ys.
EXAMPLE
1. cdp stack from disk input:
gather -N/data1/indat1 -N/data1/indat2 -N/data1/indat3 -S |
\
pred -p32 -ol200 -TV | \
cdpstk3d -Ocdp -x13000 -y12000 -x20 -y23000 -x30 -y30
-x43000 \
-y40 -vvel_tdfn -ildm50 -cldm100 -angmx20 -angmn-20 -tdfn
where the the X-axis corresponds to the receiver lines and
we go counter clockwise starting from the upper right
(northeast) corner along a receiver line. The input data is
spread out over 3 disk partitions and we use gather to
assemble them in sequence. The input stream is also passed a
time varying predictive decon. An azimuthal slice between +
& - 20deg is being rejected (perhaps this is the source of
some strong rig noise on the input data).
2. cdp from tape input:
xcram10 -r | \
cdpstk3d -Ocdp -x13000 -y12000 -x20 -y23000 -x30 -y3 0
-x43000 \
-y40 -vvel_tdfn -ildm50 -cldm100 -tdfn -mmutcrds
where the input here is from a tape stacker accessed using
xcram10. Also the velocity file is in velocity tape format
(possibly decimated to, say, every 100ms) and there is a
mute function given.
SEE ALSO
sr3d1, sr3d2, cdpvel3d, dmostk3d, dmovel3d, angst3d,
dmoangst3d
AUTHOR
Paul Gutowski (socon 422) 3146
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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