NAME
decon3d - 3D surface consistent (time varying) decon:
second pass - compute and apply filters
SYNOPSIS
decon3d [ -Nntap ] [ -Ootap ] [ -SHOTstap ] [ -GRUPrtap ] [
-XOFFxtap ] [ -dmindstmin ] [ -dmaxdstmax ] [ -ddeldstmax ]
[ -diminmindi ] [ -dimaxmaxdi ] [ -liminminli ] [ -limax-
maxli ] [ -x1x1 ] [ -y1y1 ] [ -x2x2 ] [ -y2y2 ] [ -x3x3 ] [
-y3y3 ] [ -x4x4 ] [ -y4y4 ] [ -cldmcldm ] [ -ildmildm ] [
-ppr ] [ -olol ] [ -TV ] [ -wwind ] [ -noff ] [ -V ] [ -? ]
DESCRIPTION
decon3d reads the surface consistent autocorrelations pro-
duced by predecon3d and computes the filters and applies
them. Each input trace has a source cell, a receiver cell,
and an offset bin associated with it. The autocorrelations
based on the surface consistent averages of the autocorrela-
tions of each constituent input trace have been computed and
stored on disk in the appropriate cells and bins (according
to shot, group, and offset) by predecon3d. As each input
trace is read the cells associated with its shot and
receiver are determined along with the offset bin. The auto-
correlations for the associated shot, group, and offset
locations for that trace are then averaged, and a deconvolu-
tion filter is computed and then applied to that trace. The
normalization factors are also read and applied so that the
output traces not only have been deconvolved in a surface
consistent manner but the gains have been applied in a simi-
lar manner.
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 output is in the
same sort order as the input.
It is strongly recommended that a brute NMO followed by a
mute be applied to the data prior to both predecon3d and
it's application follow-on decon3d. The moveout can be unap-
plied to the data output from the application step. The rea-
son for this is even a brute NMO tends to minimize offset
variations of the multiple periods making the above type of
operator computation much more robust.
decon3d gets both its data and its parameters from command
line arguments. These arguments specify the input, output,
decon parameters, output survey extent, spread 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'.
-SHOT stap
Enter the input decon filter disk file associated with
shots produced by a prior run of predecon3d. This input
cannot be piped.
-GRUP rtap
Enter the input decon filter disk file associated with
groups. produced by a prior run of predecon3d. This
input cannot be piped.
-XOFF xtap
Enter the input decon filter disk file associated with
offsets. produced by a prior run of predecon3d. This
input cannot be piped.
-O otap
Enter the output file name. If this is left blank an
output pipe (stdout) is assumed.
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 orienta-
tion 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 output spread
(in ft,m). The number of gathers is computed by
(dstmax-dstmin)/ddel + 1. No default.
-dmax dstmax
Enter the maximum offset to use in the output (in
ft,m). No default.
-ddel dstdel
Enter the output spread group interval (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 must set of parameters to limit the region of
interest for velocity analysis. Default is the first
and last inline bin as determined from the 4 corners of
the survey provided on the command line. But beware if
you default these parameters you need the appropriate
disk space for (limax-limin+1) * (dimax-dimin+1) *
(number groups in spread) traces.
-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. his is a must set of parameters to limit the
region of interest for velocity analysis.
-p pr
Enter the prediction distance (ms). Default = spiking.
-ol ol
Enter the operator length (ms). Recall from decon
theory that the result of predictive decon on the auto-
correlation will be to zero it from the prediction dis-
tance out to the operator length leaving the remainder
untouched. No default.
-P prew
Enter % prewhitening. This has the effect of limiting
the deconvolution spectrally as it is increased to the
larger amplitudes. Small amounts of prewhitening are
necessary to prevent the solution of the normal equa-
tions from blowing up. Default = .01
-TV Enter the command line argument '-TV' to use the time
varying decon option (you will need to input the length
of the sliding window) also.
-w wind
Enter the length (ms) of the sliding design/application
window. This window is slid down the trace 1/2 the win-
dow length at a time. The autocorrelation and subse-
quent filter application are done independently at each
window position. The resulting nwin decon filters are
stored in a single trace.
-shot
Enter the command line argument '-shot' to tell the
program shot data is being input. Currently this option
does nothing.
-noff
Enter the command line argument '-noff' to not use the
offset decon dependence, i.e. use only the source and
receiver dependent decon operations.
-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. pre-stack decon from disk input:
gather -N/data1/indat1 -N/data1/indat2 -N/data1/indat3 -S |
\
predecon3d -SHOTsht -GRUPgrp -XOFFoff -x13000 -y12000 -x20
-y23000 -x30 -y30 \
-x43000 -y40 -ildm50 -cldm100 -dmin200 -dmax6800 -ddel200
-p32 -ol200 \
-dimin28 -dimax48 -limax28 -dimax48
gather -N/data1/indat1 -N/data1/indat2 -N/data1/indat3 -S |
\
decon3d -SHOTsht -GRUPgrp -XOFFoff -x13000 -y12000 -x20
-y23000 -x30 -y30 \
-x43000 -y40 -ildm50 -cldm100 -dmin200 -dmax6800 -ddel200
-p32 -ol200 \
-dimin28 -dimax48 -limax28 -dimax48 -Ooutput
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 area of interest has been
restricted to DIs between 28 and 48 and LIs between 28 and
48 (a total of 441 cells). The first predecon3d pass builds
the decon filter files and the second pass decon3d reads
these and applies the filters.
2. pre-stack decon (first pass) from tape input:
xcram10 -r | \
decon3d -SHOTsht -GRUPgrp -XOFFoff -x13000 -y12000 -x20
-y23000 -x30 -y30 \
-x43000 -y40 -ildm50 -cldm100 -dmin200 -dmax6800 -ddel200
-p32 -ol200 \
-dimin28 -dimax48 -limax28 -dimax48 -TV -w500 -Ooutput
where the input here is from a tape stacker accessed using
xcram10. The time varying option has been used here with a
sliding window of 500ms, a prediction distance of 32ms, and
an operator length of 200ms.
SEE ALSO
predecon3d
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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