NAME
apkr - Automatic Picking of Migration Velocity Spectra
SYNOPSIS
apkr -Nmodel.env -Omodel.pks -O2model.pkpnl \
-apkr.crd"\
FORMAT FIRSTREC LASTREC REC INC RECMIX
firstrec lastrec rec inc recmix
SMOOTH ERR BIAS PEAKPOWR CUTOFF TIMSMOOTH TIMSMEXP RECSMOOTH
err bias peakpowr cutoff timsmooth timsmexp recsmooth
PATHS PATH1 PATH2 PATH3 PATH4
path1 path2 path3 path4
CONTROL P1STREC PLASTREC PRECINC TOLERANCE
p1strec plastrec precinc tolerance
VELOCITIES # OF VEL BEG VEL VEL INC
nvel beg vel vel inc
VGUIDE TIME VELOCITY
t01 v01
t02 v02
. .
. .
. .
tnvel vnvel
"
#...|....1....|....2....|....3....|....4....|....5....|....6....|....7
STARTJOB
Create a file that looks like the above synopsis with the
following command:
catpat apkr > apkr.job
Job deck apkr.job may contain many defaults for the lower
case parameter entries. Edit the job deck to suit your
needs and submit apkr.job with the following command:
startjob apkr.job
DESCRIPTION
apkr automatically picks a velocity function from panels
produced by the cubevz process. Input panels are time vs.
the envelope (an estimate of power) of stacked traces that
have been prestack migrated with several V(z) functions. A
V(z) function will be picked at every time sample using a
global evaluation method. The output picked function (col-
lection of V(z) function numbers at each sample) will maxim-
ize power along the picked path while minimizing the length
of the picked path.
The output picks dataset can be used by program p2iv to gen-
erate a corresponding V(x,z) velocity field or by program
fsi to generate a corresponding stacked section from the
cube data volume. The output picked panel dataset is for
quality control and can be viewed using xsd or xcube. It
shows each analysis panel with automatic picks encoded into
it. Manual picks can be made on the picked panels and used
as constraints in a subsequent execution of apkr.
Command line arguments
-N model.env
Enter the name of the input envelope dataset after typ-
ing -N. This is a USP-formatted dataset which has
been output from cubevz.
-O model.pks
Enter the name of the output dataset containing the
picks after typing -O.
-O2 model.pkpnl
Enter the name of the output dataset containing the
picked panels after typing -O2.
-P pickfile
Enter the name of an input "xsd" or "xcube" constraint
pick file after typing -P (this dataset is optional).
-V Enter -V for a verbose printout.
-e In most cases, the input dataset (model.env) is a set
of envelope traces. An envelope trace is the vector
product of the input trace with its hilbert transform.
Program, apkr, computes an error surface from these
envelope traces using the error bias, peak power, and
cutoff parameters. It is possible, however, to input
an error surface instead of the usual envelope traces
into program apkr. In that case, program apkr must be
told not to perform the envelope-to-error-surface com-
putation which is the purpose for this parameter. The
presence of the -e (error flag) indicates that the
input dataset is already an error surface. When this
flag is used, the error bias, peak power and cutoff
parameters are disabled.
-? Enter this (or '-?' if you are running in c-shell) to
get online help. The program will terminate after
printing this.
-h Enter -h for online help. Program will terminate after
printing this.
-apkr.crd"\
This keyword, -apkr.crd"\, must be entered exactly as
shown with no spaces after the backslash. The embedded
menu cards that follow this keyword must be typed
exactly as shown, with the lower case parameter names
being changed to the actual values you want the program
to use. All of the parameter values must be entered in
the correct columns. The double quote following the
embedded menu cards must be present as shown.
Description of Parameters
FIRSTREC firstrec
This is the first record to process from the input
dataset. The default is the first record on the input.
LASTREC lastrec
This is the last record to process from the input
dataset. The default is the last record on the input.
REC INC recinc
This is the record increment. The default is 1.
RECMIX recmix
This is the number of records to mix. If the record
increment is greater than 1, this specifies the number
of records to sum as one record. The default is one.
The maximum is the record increment.
ERR BIAS errbias
This is the stabilizing factor for inverting coheren-
cies. The input dataset is assumed to be a coherence
measurement, i.e., envelope. Recommended value: 0.10.
Error values are calculated according to:
error=
(((cutoff**peakpowr)*(1/(avg_cohrnc**peakpowr)))+errbias)/
(((cohrnc**peakpowr)*(1/(avg_cohrnc**peakpowr)))+errbias)
where: avg_cohrnc is the average coherence
cohrnc is the current coherence value
peakpowr is the peak power parameter
cutoff is the cutoff parameter converted to
coherence units
errbias is the errbias parameter
PEAKPOWR peakpowr
This parameter will power up the coherence peaks caus-
ing the picks to more closely honor the peaks. A value
of 1 results in no powering. A number greater than 1
will boost the amplitudes of the peaks. The default is
1. Recommended value: 1.8; Recommended range: 1. -- 3.
CUTOFF cutoff
This parameter is the noise level cutoff value for
coherencies. Coherence values below the cutoff are set
to the cutoff value. The default is 0.
-1 < cutoff < 0; cutoff is between minimum
and average coherence
cutoff = 0; cutoff is average coherence value.
0 < cutoff < 1; cutoff is between average and maximum
Recommended values: -1. < cutoff < .2
TIMSMOOTH timsmooth
This is the vertical smoothing parameter, a higher
number results in more smoothing on each picked record.
The default is 1.
timsmooth=delta_trace/delta_time; ratio of grid dimensions
Valid values are timsmooth > 0. Recommended values:
.005 (based on observation)
.001 -- .01
TIMSMEXP timsmexp
A value of 0 for this parameter results in the same
amount of smoothing from beginning to end of the trace.
A value of 1 results in the timsmooth effectively
increasing linearly with time. Recommend value: 1.
(based upon weak theory)
In order to change timsmexp while fixing the smoothing
value at the Kth time sample:
timsmoothnew = timsmoothold*(K**(timexpold-timexpnew)
where timexpold and timsmoothold are the values from a
previous execution of this program.
RECSMOOTH recsmooth
This represents lateral smoothing. A higher number
results in more smoothing from record to record. The
default is 1.
recsmooth=delta_trace/delta_record; ratio of grid dimensions
Valid values: recsmooth >= 0
A value of 0 will not do any lateral smoothing. Each
record will then be picked independently of surrounding
records.
Recommend range: .5 -- 5.
PATH1 PATH2 PATH3 PATH4 path1 path2 path3 path4
The values for the path parameters are:
1 - allow the path type
0 - do not allow the path type
Unless the picks are expected to change very rapidly
with time, only path2 and path3 need to be set. If
picks should always be increasing with time only path2
or path2 and path1 need be set. Recommended values:
(path2 and path3 for most seismic velocities)
(trace sample interval)
<- ->
_________________
/|\ /|\
/ | \ |
path 4 / | \ path 1 |
/ | \ delta t
/ | \ (time sample interval)
/ | \ |
/ path | path \ |
/ 3 | 2 \ \|/
path1: paths in which 1 < dx/dt ; default=0
path2: paths in which 0 < dx/dt < 1 ; default=1 (set)
path3: paths in which -1 < dx/dt < 0 ; default=1 (set)
path4: paths in which dx/dt < -l ; default=0
P1STREC p1strec
This is the first record of control point pick file
relative to the input dataset. The default is 1 (same
as model.env input file).
PLASTREC plastrec
This is the last record of control point pick file
relative to the input dataset. The default is 1 (same
as model.env input file).
PRECINC precinc
This is the record increment of control point pick file
relative to the input dataset. The default is 1 (same
as model.env input file).
TOLERANCE tolerance
This is the amount to allow picks to vary from control
points.
tolerance = 0; honor control points exactly
tolerance = n; picks must lie within n traces
of control points.
The default is 0.
GUIDE FUNCTION
The guide function defines the slope
of the picked curve in the absence
of coherence information. Any curve
that is parallel to the defined guide
function will be equally likely. The
default guide function is a constant trace.
# OF VEL nvel
This is the number of velocity perturbations to be
used.
BEG VEL begvel
This is the beginning velocity. This is used to convert
the time/velocity pairs into trace numbers which is how
the guide function is actually defined.
VEL INC velinc
This is the velocity increment used to convert
velocity/time pairs of a guide function into trace
numbers.
TIME t01.....tnvel
This is the time for the time/velocity pairs of a guide
function. The times must be in increasing order.
VELOCITY v01.....vnvel
This is the velocity for a time/velocity pair. NOTE:
To input this guide function in terms of actual trace
numbers instead of velocities (this is necessary if
each trace does not correspond to a unique velocity),
enter the trace numbers instead of velocities and set
the following:
beg vel = 1
vel inc = 1
-and-
Pick Control Points (used with the pick file
specified with -P command line option)
SEE ALSO
cubevz, vmod, cubevz.flow, apkr.flow, fsi, p2iv
BUGS
None known.
AUTHOR
Curtis Kruse
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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