NAME
gam2vel - convert horizon picks to updated velocity field
SYNOPSIS
gam2vel [ -Ninput ] [ -Ooutput ] [ -nsns ] [ -nene ] [ -rsrs
] [ -rere ] [ -P1stkpick ] [ -P2smbpick ] [ -dgammadgamma ]
[ -ngammangamma ] [ -jwinjwin ] [ -vminvmin ] [ -vmaxvmax ]
[ -ppow ] [ -agradagrad ] [ -ks ] [ -ke ] [ -dk9k ] [ -ior-
diord ] [ -V ] [ -? ] [ -h ]
DESCRIPTION
gam2vel reads an mbs-compatible depth-interval velocity
field, a set of horizon picks in xsd-format, horizon-based
semblance picks in xsd-format, and some parameters to con-
trol the velocity inversion. It outputs an updated velocity
field.
gam2vel gets the input and output file names and inversion
parameters from the command line.
Command line arguments
-Nntap
Enter the name of the mbs-compatible velocity field
after typing -N. This file is usually created in a
velocity model-building program like either xsd,
xvedit, or velin. 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 'vsp' stored on the
'b' disk.
-Ootap
Enter the updated output velocity file name immediately
after typing -O. The output semblance file requires
the full path name (see above).
-rsrs
Enter the starting record number after typing -rs.
-rere
Enter the ending record number after typing -re.
-nsns
Enter the starting trace after typing -ns.
-nene
Enter the ending trace after typing -ne.
-P1stkpick
Enter the first input xsd pick file name immediately
after typing -P1. This file should have been created
by program xsdintrp on an xsd segment file. To create
the xsd segment file, you should plot the depth-
migrated stack with program xsd, and pick the key hor-
izons on the stack. If you have an xsd segment file
from a time-section, you can convert the picks from
time to depth with program xsdt2d.
-P2sempick
Enter the second input xsd pick file name after typing
-P2. This file should have been created by program
xsdintrp on an xsd segment file. To create the xsd
segment file, you should plot the records from program
horgam with program xsd, and pick the maximum sem-
blances along each key horizon.
-dgammadgamma
Enter the increment between gammas. The default is
0.20. If you have 30 gammas, then the default gamma
scans will be +/- 30 percent because 15 (30/2) times
.020 is .3. The gamma value is a ratio of new to old
slownesses. If gamma is smaller than one, the new
slowness will be less than the old slowness; therefore;
the velocities are implied to be faster.
-ngammangamma
Enter the number of gamma scans. The default is the
number of traces per input record.
-ppow
Enter the exponent to use in Dix inversion. An
exponent of 1 implies average velocity. An exponent of
2 implies rms velocity. Only values between 1 and 2
are acceptable. The default is 2.
-vminvmin
Enter the minimum interval velocity. If the dix inver-
sion yields either a velocity less than this value or
an imaginary velocity, then the interval velocity is
set to this minimum value.
-vmaxvmax
Enter the maximum interval velocity. If the dix inver-
sion yields an interval velocity greater than this
value, then the interval velocity is set to this value.
-jwinjwin
Enter the number of samples after typing -jwin. This
value represents the number of samples in the dix
smoothing window. Each output interval velocity will
be the average interval velocity to the current depth
step, n, from the jwin previous depth steps (n-1, n-2,
..., n-jwin). This parameter works the same way as the
smoothing parameter in program xvadr.
-agradagrad
Program gam2vel performs a dix inversion and then it
tries to find a single vertical gradient for each hor-
izon and a linear v(0). You can blend the two results
with this parameter. Enter 1 to use all gradient.
Enter 0 to us all dix. Any value between 0 and 1 is
valid.
-ksks
Enter starting gradient to test. Program gam2vel finds
the k which produces the lowest standard deviation in
v(0) for a horizon. Once the best k is determined,
program gam2vel fits a least-square line to the v(0).
Default is -.5.
-keke
Enter the ending gradient to test. See explanation for
the ks parameter. The parameter k=dv/dz. Default is
1.5.
-dkdk
Enter the gradient increment. Program gam2vel will
test all gradients from ks to ke at an increment of dk.
The default is .1.
-iordiord
Enter the order for the polynomial fit. The default is
0 (No fit).
-V Enter the command line argument '-V' to get additional
printout.
-? Enter this (or '-?' if you are running in c-shell) to
get online help. The program will terminate after
printing this.
-h Enter this option to get online help. The program will
terminate after printing this.
SEE ALSO
xsdd2t, xsdt2d, xsdintrp, horgam, xsd2xtpick, appgam, norm,
envelop
BUGS
Unknown
AUTHOR
Gary Murphy
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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