NAME
piestkt - Pie Filter and Power Stack Seismic Records
SYNOPSIS
piestkt -Ninput -Ooutput -VTvelocity.tape \
-piestkt.crd"\
PIES ITYPE MSTRT MEND MINC IPAD IGMIX IPOW
itype mstrt mend minc ipad igmix ipow
GSCL ALPHA XMULT EXPNT
alpha xmult expnt
FILT DX DZ F1 F2 F3 F4 RAMP
dx dz f1 f2 f3 f4 ramp
ANGLES NUM ANGLE BEAMWIDTH WEIGHT
n1 ang01 bw weight
n2 ang02 bw weight
n3 . . .
. . . .
. . . .
nv angnv bw weight
"
#...|....1....|....2....|....3....|....4....|....5....|....6....|....7
STARTJOB
Create a file that looks like the above synopsis with the
following command:
catpat piestkt > piestkt.job
This job file will have some suggested parameter values
entered. Edit your piestkt.job to suit your needs and sub-
mit piestkt.job with the following command:
startjob piestkt.job
DESCRIPTION
piestkt applies a pie filter in the (kx,kz) domain and power
stacks the data. Input data are prestack migrated common
angle depth sections (output from programs kmpw, fxpwmig, or
pwmvzn).
The primary use of this program is to filter out low fre-
quency wavelet stretch resulting from far offset prestack
migration without simultaneously eliminating low frequency
reflection data and to preferentially retain near-normal
incidence data for any given constant angle record. Program
piestkt reads parameters from embedded menu cards as shown
above and command line arguments described below. Program
steps are as follows:
1) Read depth section(s), which are in USP format.
These are constant angle migrated prestack records
(output from kmpw, fxpwmig, or pwmvzn).
2) Read velocity field, which is in USP format.
3) Read filtering parameters.
4) Stretch input depth section from variable velocity
background to a constant velocity background. The
constant velocity used is determined by the program.
5) Fourier transform data into the (kx,kz) domain
6) Filter data using a radial pass filter to remove low
and/or high wave number components from the data.
7) Cut a piece of the pie by rejecting all dips outside
of the bandwidth about the selected angle.
8) Inverse Fourier transform data to the (x,z) domain.
9) Unstretch depth section back to the original
velocity background.
10) Perform a 2-trace mix of the data. (optional)
11) Perform a power stack of the data.
12) Apply a constant gain curve to the data. (optional)
Gain curve is of the form:
(xmult)*(10**expnt)*(z**alpha)
where z is depth, and xmult, expnt, and alpha are
user-supplied parameters.
13) Write out the stacked corrected data in USP format.
Command line arguments
-N input
Enter the input dataset name after typing -N. These are
constant angle prestack migrated depth sections in USP
format.
-O output
Enter the output dataset name after typing -O. This is
a stacked migrated and filtered depth section.
-VT velocity.tape
Enter the velocity dataset name after typing -VT. This
is a USP-formatted dataset where sample values are
interval velocities.
-V Enter -V for a verbose printout.
-piestkt.crd"\
This keyword, -piestkt.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 parameters must be in the
correct columns. The double quote following the embed-
ded menu cards must be present as shown.
Description of Parameters
ITYPE itype
The ITYPE value.
0 = power stack, no pie filter.
1 = power stack, pie filter
MSTRT mstrt
The first record of the input to use. Default is 1.
MEND mend
The last record of the input to use. Default is the
value specified in the line header as the number of
records.
MINC minc
The record increment. Default is 1.
IPAD ipad
The flag indicating whether or not to pad the traces
with zeroes.
0 = no extra padding
>0 = padded to next power of 2
IGMIX igmix
This is the flag indicating whether or not to mix
traces.
0 = do not perform a 2-trace average on output
>0 = a 2-trace average will be performed on output.
IPOW ipow
The power exponent for summing.
ipow > 1 => higher amplitudes boosted
ipow = 1 => no power summing
ipow < 1 => lower amplitudes boosted
ALPHA alpha
The depth ramp exponent for scaling the output,
where scalar = (xmult)*(10**expnt)*(z**alpha).
.nf
The constant multiplier value,
where scalar = (xmult)*(10**expnt)*(z**alpha).
Default is 1.
EXPNT expnt
The exponent for an exponential gain curve,
where scalar = (xmult)*(10**expnt)*(z**alpha).
The trace spacing value (in ft or meters).
The depth sample spacing (in ft or meters).
F1 F2 F3 F4 f1 f2 f3 f4
The points of the trapezoidal filter.
RAMP ramp
The wavelength ramp for wedge (i.e., how wide is the
taper on the 2 edges of the pie?).
Default = (2*pi*f4)/(vmin/2).
n1,n2....nv
These values represent the record number for the
corresponding angle. The values are necessary but are
not checked for accuracy. Records for which no card is
supplied will take their beamwidths and weights from
the previous card.
ANGLE ang01,ang02....angnv
These values represent the angle for the corresponding
record. They should match the angles on the input
dataset.
BEAMWIDTH bw
The beamwidth (in degrees) for calculating the size of
the pie filter wedge. A suggested value is 10 degrees.
WEIGHT weight
The weight to be applied to each record. For no spe-
cial weighting, set this value to be the same (prefer-
ably 1) for each record.
SEE ALSO
mbs, startjob, beginjob, endjob, dskft
BUGS
None known.
AUTHOR
Ron D. Coleman, Mary Ann Thornton
COPYRIGHT
copyright 2001, Amoco Production Company
All Rights Reserved
an affiliate of BP America Inc.
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