NAME
velint - take input 3D or 2D sparse velocity field and
interpolate (infill) functions
SYNOPSIS
velint [ -Nntap ] [ -Ootap ] [ -nsnstr ] [ -nenetr ] [
-rsnrst ] [ -renred ] [ -twod ] [ -V ] [ -? ]
DESCRIPTION
velint takes an intermediate velocity field (e.g. one
created using zmapvel2sis or vomit or velin) and interpo-
lates over a user specified survey area so that there will
be a velocity trace at every grid location. The intermediate
velocity field consists of velocity traces only at the loca-
tions specified by the input velocity functions, e.g. bfile
format functions. This is fine for some applications but the
user may require a more dense velocity volume.
The default mode of the program is 3D where the velocity
functions are assumed to correspond to the grid built from
line and trace limits supplied by the user. In 2D mode the
program reads either record or trace limits to establish the
line indexing. Each function is then located along the line
and each index between functions will result in an interpo-
lated velocity trace output.
For 3D the user defines the limits of the survey grid by
supplying the start/end line and the start/end trace. The
survey area of the output volume must therefore be a rectan-
gle. If the area is larger than the entent of the intermedi-
ate velocity file then the output volume is extrapolated to
the boundaries. If the specified area is within the entent
of the intermediate velocity file then the output volume
will be truncated.
For 3D the input data must be organized so that each line is
a record (i.e. has the same RecNum value). All records must
be the same length, i.e. have the same number of velocity
traces (or padded with dead traces to be the same length).
The velocity traces must currently occur at the same trace
numbers on all the lines. If a short record is encountered
the program emits a message and quits. The user should then
use pad piped into velint to make the records all the same
size. In the 2D case the input data can be either one record
of N traces or N single trace records.
The 3D output grid is defined by the line start and end and
the trace start and end. The 2D indexing is specified either
by the start/end line entries or the start/end trace entries
depending on how the input velocity tape is organized (one
record or multiple single trace records).
velint gets both its data and its parameters from command
line arguments. These arguments specify the output survey
dimensions, and verbose printout, if desired.
Command line arguments
-N ntap
Enter the input velocity USP 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. The
input records must correspond to lines and all records
must be of the same size. 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 interpolated velocity USP 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).
-ns nstr
Enter the start trace number. This and the next 3
entries define the boundaries of the output interpo-
lated survey. No default in the 3D case. In the 2D
case this the start of the trace indexing. If this and
the -ne[] entry below are not zero then the output will
be a single record composed of ne - ns + 1 traces. The
default header word in this case will be TrcNum.
-ne netr
Enter the end trace number of the output survey. No
default in the 3D case. In the 2D case this is the end
of the trace indexing. The default header word in this
case will be TrcNum.
-rs nrst
Enter start line number of the output survey. No
default in the 3D case. In the 2D case this the start
of the record indexing. If this and the -re[] entry
below are not zero then the output will be re - rs + 1
single trace records. The default header word in this
case will be RecNum.
-re nred
Enter end line number of the output survey. No default
in the 3D case. In the 2D case this is the end of the
record indexing. The default header word in this case
will be RecNum.
-twod
Enter the command line argument '-twod' to turn on the
2D mode. Then the command line entry will be either
-ns[] -ne[] or -rs[] -re[] depending on whether the
input velicity tape is a single record or multiple sin-
gle trace records.
-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.
EXAMPLES
zmapvel2sis -Nu4e.stkvbase -B -si4 -vmin1500 | pad -Ovel-
file1
where the intermediate velocity file has been generated from
a BFILE set of functions (we need to force a surface velo-
city using -vmin[] since the file is metric and the default
surface velocity that would have been inserted into the
functions is 4850). The pad is to fill out any short records
from zmapvel2sis since velint only takes square data.
We then run
velint -Nvelfile1 -Ovelout -ns1 -ne98 -rs101 -re141
where the survey limits are lines 101 to 141 inclusive, and
traces 1 to 98 inclusive.
As an example of a 2D run we take a TDFN velocity function
and convert if to USP format:
vomit -Ntdfn.all -Ojunkv -fitdfn -fousp -nrec3 -ntrc1 \
-nsamp500 -nsi2
velint -Njunkv -Ojunkvv -rs1 -re166 -twod
where we have taken the vomit USP output which consists of
single trace records and mapped them onto a line index
starting from the default RecNum = 1 to RecNum = 166.
BUGS
Currently cannot handle irregular lines, i.e. the functions
are not at the same trace numbers on each line. Check your
Bfile for regularity.
SEE ALSO
zmapvel2sis
AUTHOR
Paul Gutowski, APR (socon 422-3146)
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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