NAME
dmostk3d - true amplitude 3D dmo stack
SYNOPSIS
dmostk3d [ -Nntap ] [ -Ootap ] [ -vvtap ] [ -tdfn ] [ [
-dmindstmin ] [ -dmaxdstmax ] [ -ddeldstdel ] [ -dipmangmax
] [ -diminmindi ] [ -dimaxmaxdi ] [ -liminminli ] [ -limax-
maxli ] ] [ -x1x1 ] [ -y1y1 ] [ -x2x2 ] [ -y2y2 ] [ -x3x3 ]
[ -y3y3 ] [ -x4x4 ] [ -y4y4 ] [ -cldmcldm ] [ -ildmildm ] [
-AS ] [ -CSA ] [ -COA ] [ -BKA ] [ -GS ] [ -R ] [ [ -norm ]
[ -Tttap ] [ -dexpdexp ] ] [ -V ] [ -? ]
DESCRIPTION
dmostk3d is a dmo implementation from the Colorado School of
Mines Center for Wave Phenomena. It is basically a born-
type algorithm that takes input data in any form (shot, cdp,
etc), an RMS velocity field, and outputs a zero offset (dmo
stack) true amplitude section.
As each input trace is read in the amplitudes are corrected
for the type of spreading desired and then sprayed out along
the dmo ellipse accumulating in the proper CMP bin locations
in time in the output array. Optional correction can be
made for the number of live samples in the accumulating sum.
Unlike some dmo codes no prior NMO correction is applied;
this is all done internally (which is why we need the RMS
velocity field).
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. The SrRcMX and
SrRcMY are optional since they can be calculated internally.
For data in shot order it is assumed that all basic correc-
tions have been made, e.g. refraction statics, velocity
analysis, residual statics. Other processes such as deconvo-
lution and filtering can be done on the fly before input
into the DMO.
dmostk3d gets both its data and its parameters from command
line arguments. These arguments specify the input, output,
the dmo velocity, output survey extent, spreading options,
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 dmo 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 dmo 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 dmo 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).
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 (X or 2-3 side) cell dimension
(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.
Remember when setting up the coordinate system the line
joining Corner (1) to Corner (2) should be clockwise in
the direction of a receiver or shot line. No default.
-ildm ildm
Enter the inline (1-2 side) 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. Remember when set-
ting up the coordinate system the line joining Corner
(1) to Corner (2) should be clockwise in the direction
of a receiver or shot line. No default.
-dmin dstmin
Enter the minimum offset to use in the DMO (in ft,m).
Default is to use the smallest offset.
-dmax dstmax
Enter the maximum offset to use in the DMO (in ft,m).
Default is to use the largest offset.
-ddel dstdel
Enter the offset increment to use in the DMO (in ft,m).
No default.
-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..
-dipm dipm
Enter maximum dip (degrees) to process. Default = 90.
-AS If present on the command line turn off the anti alias
constraints and process all dips.
-CSA If present on the command line apply common shot ampli-
tude term. This is also the default. Note: either this
option or the common offset option below both preserve
amplitudes well; use of the kinematic term will not be
so nice to the amplitudes but the code will run some-
what faster. Default is to use no amplitude term.
-COA If present on the command line apply common offset
amplitude term.
-BKA If present on the command line apply Kirchhoff
kinematic amplitude term.
-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 DMO run can be continued at
the point at which it stopped without the previous data
being wiped.
-GS If present on the command line use geometric spread,
otherwise zero offset spreading will be used.
-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 DMO 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. DMO stack from disk input:
gather -N/data1/indat1 -N/data1/indat2 -N/data1/indat3 -S |
\
dmostk3d -Odmo -x13000 -y12000 -x20 -y23000 -x30 -y30
-x43000 \
-y40 -vvel_tdfn -ildm50 -cldm100 -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.
2. DMO from tape input:
xcram10 -r | \
dmostk3d -Odmo -x13000 -y12000 -x20 -y23000 -x30 -y3 0
-x43000 \
-y40 -vvel_tdfn -ildm50 -cldm100 -tdfn
where the input here is from a tape stacker accessed using
xcram10.
SEE ALSO
sr3d1, sr3d2, dmovel3d
AUTHOR
Paul Gutowski using DMO amplitude formulation due to Chris
Liner, formerly Colorado School of Mines
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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