SYNOPSIS
PERL PROGRAM NAME:
AUTHOR: Juan Lorenzo (Perl module only)
DATE:
DESCRIPTION:
Version:
USE
NOTES
Examples
SYNOPSIS
SEISMIC UNIX NOTES SUBACKUS - calculate Thomsen anisotropy parameters from
well log (vp,vs,rho) data via BACKUS averaging
subackus < vp_vs_rho.su >stdout [options]
Required parameters:
none
Optional parameter:
navg=201 number of depth samples in Backus avg window
all=0 =1 to output extra parameters
(<vp0>,<vs0>,<rho>,eta,vang,a,f,c,l,A,B,<lam>,<mu>)
ang=30 angle (deg) for use in vang
Notes:
1. Input are (vp,vs,rho) traces in metric units
2. Output are (epsilon,delta,gamma) dimensionless traces
tracl=(1,2,3)=(epsilon,delta,gamma)
(all=1 output optional traces listed below)
tracl=(4,5,6,7,8)=(vp0,vs0,<rho>,eta,vang)
tracl=(9,10,11,12)=(a,f,c,l)=(c11,c13,c33,c44) backus avg'd
tracl=(13,14)=(<lam/lamp2mu>^2,4<mu*lampmu/lamp2mu>)=(A,B)
used to analyze eps=(a-c)/2c; a=c11=A*x+B; c=c33=x
tracl=(15,16)=(<lambda>,<mu>)
for fluid analysis (lambda affected by fluid, mu not)
tracl=(17,18,19)=(vp,vs,rho) orig log values
tracl=(20)=(m)=(c66) Backus avg'd
tracl=(21,22,23,24,25)=(a,f,c,l,m)=(c11,c13,c33,c44,c66) orig
3. (epsilon,delta,etc.) can be isolated by tracl header field
4. (vp0,vs0) are backus averaged vertical wavespeeds
5. <rho> is backus averaged density, etc.
6. eta = (eps - delta) / (1 + 2 delta)
7. vang=vp(ang_deg)/vp0 phase velocity ratio
The idea being that if vang~vp0 there are small time effects
(30 deg comes from ~ max ray angle preserved in processing)
Example:
las2su < logs.las nskip=34 nlog=4 > logs.su
suwind < logs.su key=tracl min=2 max=3 | suop op=s2vm > v.su
suwind < logs.su key=tracl min=4 max=4 | suop op=d2m > d.su
fcat v.su d.su > vp_vs_rho.su
subackus < vp_vs_rho.su > eps_delta_gamma.su
In this example we start with a well las file containing
34 header lines and 4 log tracks (depth,p_son,s_son,den).
This is converted to su format by las2su. Then we pull off
the sonic logs and convert them to velocity in metric units.
Then the density log is pulled off and converted to metric.
All three metric curves are bundled into one su file which
is the input to subackus. ",
Related codes: sulprime subackush
Credits:
UHouston: Chris Liner
I gratefully acknowledge Saudi Aramco for permission
to release this code developed while I worked for the
EXPEC-ARC research division.
References:
Anisotropy parameters: Thomsen, 2002, DISC Notes (SEG)
Backus Method: Berryman, Grechka, and Berge, 1997, SEP94User's notes (Juan Lorenzo) untested
CHANGES and their DATES
Import packages
instantiation of packages
Encapsulated hash of private variables
sub Step
collects switches and assembles bash instructions by adding the program name
sub note
collects switches and assembles bash instructions by adding the program name
sub clear
sub all
sub ang
sub eps
sub eta
sub key
sub navg
sub nskip
sub tracl
sub vang
sub get_max_index
max index = number of input variables -1