NAME
cubevz - Create a V(z) Velocity Cube
SYNOPSIS
cubevz [-Ninput] [-Ooutput] [-VELvelocity] [-V] [-Ccardfile]
DESCRIPTION
cubevz is one program in the cubevz process. This process
was designed to produce a V(x,z) velocity field that can be
used as input to poststack or prestack depth migration pro-
grams.
cubevz uses a prestack V(z) depth migration algorithm to
migrate a number of constant angle time sections with a
number of input velocity functions. Inputs are the constant
angle time sections from program slnt, a velocity dataset
from program vmod, command line arguments, and a set of
parameters read from cards. The output panels are functions
of time and velocity. For each velocity function input, one
output panel will be produced which will be a representation
of all of the angles migrated using that particular velocity
function. Each trace in the output panel will be a sum of
all of the angles after the migrations are performed.
The next step in the process is to produce panels that are
functions of time and envelop using programs angs and
envelop. The last step in the process is to "pick" velocity
functions and create the final V(x,z) velocity field. The
panels are automatically picked using programs apkr, p2iv
and fsi.
There are two stages and several programs involved in the
total cubevz process. Each program in the process may be
executed by itself, but scripts are available which make it
easier for users to execute the complete process at once.
The script for the first stage is called cubevz.flow, and it
will execute the following programs: vmod, cubevz, angs and
envelop. The script for the second stage is apkr.flow. It
will execute programs apkr, p2iv and fsi. See the man pages
for these scripts and programs for further information.
Command line arguments
-N input
Enter the name of the input after typing -N. This data
should be in USP format and should be constant angle
prestack time sections.
-O output
Enter the name of the output V(z) migrated suite
dataset after typing -O.
-VEL velocity
Enter the name of the input velocity dataset after typ-
ing -VEL. This dataset must have been created with
program vmod. A vmod record is a suite of V(z) velo-
city functions.
-V Enter -V for a verbose printout.
-C If the parameters are in an external card file, enter
the name of the card file after typing -C, or by using
the catpat command a script file will be created which
will contain the command line arguments and the other
necessary parameters for executing cubevz. The script
file may then be edited to enter the correct values.
The script file may be executed using the "startjob"
command.
The Script file format:
cubevz -Ninput -Ooutput -VELvtape\
-cubevz.crd"\
TIME ENDTIMEMS PADTIMEMS BEGTIMEMS MIGTIMEMS
TIME endtime padtime begtime migtime
FREQUENCY MINFREQHZ F2FREQHZ F3FREQHZ MAXFREQHZ
FREQUENCY f1 f2 f3 f4
WIDTH BEGTRACE ENDTRACE PADTRACE DELTAX
WIDTH begtrace endtrace padtrace deltax
RECORDS BEG REC END REC INC REC
RECORDS begrec endrec increc
ANGLES # ANGLES START INCREMENT BEAMWIDTH REF VEL
ANGLES nang start anginc bw vref
T SCALE ALPHA XMULT
T SCALE alpha xmult
"
#...|....1....|....2....|....3....|....4....|....5....|....6
Description of Parameters
ENDTIMEMS endtime
This value is in ms. Should be <= maximum time on
input. Default is time on input.
PADTIMEMS padtime
This value is amount of time in ms to zero pad traces.
Recommended default is 0.
BEGTIMEMS begtime
This value is in ms. Should be positive. Used mainly
for model data.
MIGTIMEMS migtime
This value is the end time (in ms) for the migration.
FREQUENCY f1 f2 f3 f4
The points of a trapezoidal filter.
BEGTRACE begtrace
This is the first trace to use from the input records.
Default is 1.
ENDTRACE endtrace
This is the last trace to use from the input records.
Default is number of traces per record.
PADTRACE padtrace
This is the number of zero traces to pad to reduce spa-
tial wraparound.
This is the trace spacing ( ft or meters). No default.
BEG REC begrec
This is the first record to use from the input.
Default is 1.
END REC endrec
This is the last record to use from the input. Default
is the number records in line header.
REC INC recinc
This is the record increment. Default is 1.
# ANGLES nang
This is the number of angles on the input dataset. MUST
MATCH INPUT.
RT start
This is the starting angle (in degrees) on the input
dataset. MUST MATCH INPUT.
INCREMENT anginc
This is the angle increment (in degrees) on the input
dataset. MUST MATCH INPUT.
BEAMWIDTH bw
This is the beamwidth (in degrees) used for dip filter-
ing. The reflected field is dip filtered around the
normal incidence ray; the angular pass zone is
BEAMWIDTH wide (in degrees). If bw value is near 0,
only normal incidence data will be passed. Reflections
from flat layers with emergent angles greater than 2*bw
will be attenuated.
REF VELOCITY vref
This is the reference velocity (ft/sec or m/sec) as
specified for program slnt. This must be correct.
ALPHA alpha
The T SCALE cards are optional. The presence of this
card allows time scaling of the input data. This value
represents an exponent for the scaling.
T
This value represents a constant multiplier for the time scaling
of
the input data.
SEE ALSO
cubevz.flow, vmod, angs, envelop, apkr.flow, apkr, p2iv, fsi
BUGS
None known.
AUTHOR
Ron D. Coleman, Curtis Kruse, Mary Ann Thornton
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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