NAME
horpred - do predictive deconvolution on seismic traces
driven by trace header times
SYNOPSIS
horpred [ -Nntap ] [ -Ootap ] [ -hwhdrwrd ] [ -psps ] [
-pepe ] [ -Pprew ] [ -vvel ] [ -sist ] [ -eiend ] [ -nsnstr
] [ -nenetr ] [ -rsnrst ] [ -renred ] [ -G ] [ -S ] [ -C ] [
-B ] [ -V ] [ -? ]
DESCRIPTION
horpred does predictive deconvolution of selected seismic
traces using trace header times to define the prediction
distance. The aim here is to focus the decon operator on a
specific multiple (usually a water bottom) so that only a
small region about the trace header time on the autocorrela-
tion is affected.
The trace header times are assumed to have been inserted by
a previous step will usually (but not always) be defined by
picks made on a stack section. In the 2D case this can be
done using xsd on a stack then using recshift to insert the
picks into a trace header word (default is WDepDP). In the
3D case xsd can also be used along with recshift by picking
control lines through the volume and using the 3D features
in recshift. Horizon pick files from the interpretive works-
tations can also be used using tim2hed3d to insert picks.
Since the decon is applied in X-T space the multiple periods
must be stabilized in both space and time. The only way to
do this in this domain is by applying NMO designed to flat-
ten the events you wish to deconvolve (and then of course
unapply after decon). An internal means of doing this uses a
quadratic interpolator in the NMO operation and will have
slight errors. Ths optimum way is to apply NMO externally
using bdnmo and then unapply NMO on the output from horpred.
Default is not to use the internal NMO.
horpred gets both its data and its parameters from command
line arguments. These arguments specify the input, output,
the start and end prediction times, the design window, the
start and end traces, and verbose printout, if desired.
The record and trace limits specify what part of each record
or what part of the line is to be precessed through the pro-
gram. The data outside these limits will be passed
untouched.
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 data set name or file immediately
after typing -O. This output file is not required when
piping the output to another process. The output data
set also requires the full path name (see above).
-ps ps
Enter the time in ms less than the trace header time
defining the start of the multiple event. Default =
48ms. This value could be zero in which case the multi-
ple will be assumed to begin exactly twice the trace
header time.
-pe pe
Enter the time in ms greater than the trace header time
defining the end of the multiple event. This time plus
the trace header time defines the total operator length
(gap plus actual operator). After decon the zone on the
autocorrelation ps millisecs before the header time
through pe millisecs after the header time will be
zeroed out. Default = 48ms.
-hw hdrwrd
Enter trace header word mnemonic containing the trace
header time. The actual start time will be the sum of
this time and the command line constant start time. The
trace header times are assumed to have been inserted by
a previous step will usually (but not always) be
defined by picks made on a stack section. In the 2D
case this can be done using xsd on a stack then using
recshift to insert the picks into the trace headers. In
the 3D case xsd can also be used along with recshift by
picking control lines through the volume and using the
3D features in recshift. Horizon pick files from the
interpretive workstations can also be used using
tim2hed3d to insert picks. Default = WDepDP
-P prew
Enter the prewhitening as a fraction. This is neces-
sary to prevent numerical instabilities in the calcula-
tions. The effect on the output traces of increasing
prew is an overall smoothing of the data. The default
is .01.
-s ist
Enter the start time of the design window. The default
is the beginning of the trace. Optionally the start
time can be set to the trace header time used above.
-e iend
Enter the end time of the design window. The default
is the end of the trace.
-v vel
Enter the optional internal normal moveout velocity.
Since the decon is applied in X-T space the multiple
periods must be stabilized in both space and time. The
only way to do this in this domain is by applying NMO
designed to flatten the events you wish to deconvolve.
An internal means of doing this uses a quadratic inter-
polator in the NMO operation and will have slight
errors. Ths optimum way is to apply NMO externally
using bdnmo and then unapply NMO on the output from
horpred. Default is not to use the internal NMO.
-ns nstr
Enter the start process trace number. Trace numbers
below this value will not be processed. The default is
1.
-ne netr
Enter the end process trace number. Trace numbers
above this value will not be processed. The default is
the last trace number on the input data set.
-rs nrst
Enter start process record number. Record numbers below
this value will not be processed. Default value is the
first record.
-re nred
Enter end process record number. Record numbers above
this value will not be processed. Default value is
last record.
-G Enter the command line argument '-G' to apply the decon
operator only within the design window. Sometimes
better results can be obtained with this option if the
data are first approximately nmo-flattened (primary or
multiples), decon'd, then nmo-unflattened. This causes
the multiple periods to be more stable with time and
range and therefore result in less manifestation of
seams cutting across events corresponding to the design
window boundaries.
-S Enter the command line argument '-S' to fix the design
window start time to the trace header time. Default is
to use the global command line value.
-C Enter the command line argument '-C' to apply cosine
bell taper to the autocorrelation
-B Enter the command line argument '-B' to apply bartlett
(linear) taper to the autocorrelation
-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.
EXAMPLE
bdnmo -Nin_data -vmultvel |\
horpred -ps48 -pe144 -S -B |\
bdnmo -vmultvel -R -Oout_data
where an external NMO using the multiple velocity is applied
first and where the operator is defined as starting 48ms
before the trace header time and ending 144ms after the
trace header time (192ms total). The total operator length
will be the trace header time + 144ms. The last step is to
unapply the multiple NMO.
BUGS
Currently for 3D data the Landmark is the only interpretive
workstation horizon file format supported,
SEE ALSO
recshift, flatten, tim2hed3d
AUTHOR
Paul Gutowski, zprg03@trc.amoco.com, socon 422-3146
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
Man(1) output converted with
man2html