NAME
pred - module to do predictive deconvolution on seismic
traces
SYNOPSIS
pred [ -Nntap ] [ -Ootap ] [ -Fotap2 ] [ -ppr ] [ -olol ] [
-Pprew ] [ -vsvel ] [ -vevel ] [ -sist ] [ -eiend ] [
-nsnstr ] [ -nenetr ] [ -rsnrst ] [ -renred ] [ -TV ] [
-wlslide ] [ -G ] [ -S ] [ -C ] [ -B ] [ -W ] [ -H ] [
-hwhdrwrd ] [ -flt ] [ -V ] [ -? ]
DESCRIPTION
pred does predictive deconvolution of selected seismic
traces and will generate either the standard prediction
error output or optionally the predictable part of the sig-
nal. The prediction filter is designed within a user speci-
fied window defined by a start times derived by four basic
options described below.
Pred gets both its data and its parameters from command line
arguments. These arguments specify the input, output, the
design window, the start and end traces, and verbose prin-
tout, 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).
-F otap2
Enter the optional file name for the prediction error
filter. Each trace will corrspond to the filter com-
puted based on the input trace; the number of samples
is arbitrarily set to be twice the number of points in
the filter. By using program lsqinv the filter can be
inverted to get the wavelet (see also minent). Note: if
-ns/-ne/-rs/-re limits are specified then the filter
output will ve set to zero for traces outside these
limits.
-p pr
This is the wavelet length or the prediction distance
in ms (if pr is greater than or equal to zero) or zero
crossings (if pr less than zero). An entry of 0 ms will
result in a unit prediction filter being applied. Care
should be taken to make this entry correspond approxi-
mately to the nth zero crossing of the trace (using the
zero crossing option is not always a guarantee). Run-
ning auto -L[] | zeco | xgraph can be very diagnostic.
-ol ol
Enter the operator length in ms. This entry should
span the multiple period of interest.
-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. The design window start
time can be:
(1) a constant value (read off the command line),
(2) be driven by a constant value + times derived from
trace distances and a user supplied velocity (see -v
command entry below),
(3) be driven by a constant value + time extracted from
a header word in each trace (use recshift or flatten to
insert xsd pick times), or
(4) be driven by a constant value + times derived from
the water depth trace header entry and the user defined
velocity below. Only one of the above 4 choices can be
made.
Any combination of the above options will also work,
the only restriction is that only one velocity can be
used.
The start time units must be consistent with the input
sample interval.
-e iend
Enter the end time of the design window. The default
is the end of the trace.
-vs svel
Enter the design window start velocity in m or ft/s.
Default is infinite velocity or constant start time for
each trace.
-ve evel
Enter the design window end velocity in m or ft/s.
Default is infinite velocity or constant end time for
each trace.
-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.
-TV Enter the command line argument '-TV' to apply time
varying predictive decon (see required parameter
below). With this option all design window parameters
above still apply although the decon is applied only
within the design window. The -G, -S options below and
the optional operator output above are ignored.
-w lslide
Enter length (ms) of the sliding window. Effectively a
decon is done for each window postion on the trace; the
window is moved down by 1/2 its length and the decon is
computed again. The individual results are merged
together by linear interpolation. To see large effects
the sliding window length should be longer than the
operator length.
-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 output the
predictable part of the signal, otherwise the standard
unpredictable part or prediction error will be output.
With this option you cannot use the -G option above.
-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
-W Enter the command line argument '-W' to key the start
time to the trace header entry for water depth above
cdpth point. The actual window start time will be the
sum of this time and the command line constant start
time If this option is turned on and the user does not
supply a velocity (-vs[]) the line header entry is
examined for a valid velocity (program quits if this is
not found).
-H Enter the command line argument '-H' to key the start
time on the time found in the header word specified
below.
-hw hdrwrd
Enter trace header word mnemonic containing design win-
dow start time. The actual start time will be the sum
of this time and the command line constant start time.
-flt Enter the command line argument '-flt' if the -hw[]
header work is in a floating point trace header slot
(for instance those created using the Landmark horizon
extraction program lm3dhrztosis or its Geoquest coun-
terpart iesx3dhrztosis).
-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.
NOTE 1:
If the line header value SmpInt>16, it is assumed to be in
microseconds rather than in milliseconds. All command line
arguments are in milliseconds.
SEE ALSO
taupred, avepred, arde, minent, recshift, flatten
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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