pdf 2.5M - Madagascar

Sigsbee2 Models
Trevor Irons
Data Type: 2D model and acoustic finite difference synthetic data set with constant density
Source: SMAART consortium comprised of BHPBilliton Petroleum, BP, and the ChevronTexaco Exploration and Production Technology Company
Location: http://www.delphi.tudelft.nl/SMAART/sigsbee2a.htm
Format: SEGY and Native
Date of origin: Data were publicly released between September 2001 and November 2002.
INTRODUCTION
The Subsalt Multiples Attenuation and Reduction Technology Joint Venture (SMAART
JV) publicly released several data sets between September 2001 and November 2002. These
synthetic data model the geologic setting found on the Sigsbee escarpment in the deep water
Gulf of Mexico. Additional information may be found at: www.delphi.tudelft.nl/SMAART/.
The data sets remain the property of SMAART and are used under the agreement found
at the SMAART site listed above.
The file sigsbee/FILES lists all files contained in the Sigsbee2 repository of Madagascar
and is reproduced below in Table 1. Any of these files may be downloaded to local machines
using ftp protocols.
The Sigsbee2 data are separated into two distinct categories, A and B. They share
the same general model geometry and structure, however, the A model has a soft water
to seafloor boundary while the B model features a more realistic hard boundary. As a
result data produced in the B model features multiple events. The Sigsbee2B data set was
featured in paper SP3.8 ”Observations from the Sigsbee2B synthetic data set” at the 2002
SEG meeting in Salt Lake City.
SIGSBEE MODELS
This model contains a sedimentary sequence broken up by a number of normal and thrust
faults. Additionally, there is a complex salt structure found within the model that results
in illumination problems when processing and migrating the data.
The Sigsbee2A model features an absorbing free surface condition and a weaker than
normal water bottom reflection, resulting in data do not contain free surface multiples and
less than normal internal multiples. The Sigsbee 2B model uses the same structural model
as Sigsbee2A but the velocity contrast at the water bottom has been increased to a normal
level thus generating significant internal and free surface multiples. Modeling on the 2B
model was performed with both free and non free surface boundary conditions.
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9 5 2 7 5 1 7 6 0 2005−04−20 0 7 : 4 2 s i g s b e e 2 a n f s . s g y
1 0 7 6 2 4 5 2 2005−04−20 0 7 : 4 2 s i g s b e e 2 a m i g v e l . s g y
9 5 1 2 5 4 1 6 0 2005−04−20 0 7 : 4 4 s i g s b e e 2 b f s . s e g y
1226 2005−04−20 0 7 : 4 4 sigsbee2a README . t x t
3 2 7 6 8 2005−04−20 0 7 : 4 4 s i g s b e e 2 a r e a d m e . doc
1 4 2 5 9 2 0 2005−04−20 0 7 : 4 4 s i g s b e e 2 a . ppt
1 6 1 4 9 4 4 4 2005−04−20 0 7 : 4 4 s i g s b e e 2 a s t r a t i g r a p h y . s g y
1 0 7 6 2 4 5 2 2005−04−20 0 7 : 4 4 s i g s b e e 2 a m i g r a t i o n v e l o c i t y . s g y
2 1 3 5 6 1 2005−04−20 0 7 : 4 4 s i g s b e e 2 b m i g r a t i o n v e l o c i t y . j p g
1 6 1 4 9 4 4 4 2005−04−20 0 7 : 4 4 s i g s b e e 2 a r e f l e c t i o n c o e f f i c i e n t s . s g y
1 0 7 6 2 4 5 2 2005−04−20 0 7 : 4 4 s i g s b e e 2 b m i g r a t i o n v e l o c i t y . s e g y
3 3 5 9 9 4 2005−04−20 0 7 : 4 5 s i g s b e e 2 b r e f l e c t i o n c o e f f i c i e n t s . j p g
7668 2005−04−20 0 7 : 4 5 s i g s b e e 2 b r e a d m e . t x t
3 4 8 1 6 2005−04−20 0 7 : 4 5 s i g s b e e 2 b r e a d m e . doc
9 5 1 2 5 4 1 6 0 2005−04−20 0 7 : 4 5 s i g s b e e 2 b n f s . s e g y
2 4 5 8 8 8 2005−04−20 0 7 : 4 5 s i g s b e e 2 b s t r a t i g r a p h y . j p g
3 1 7 0 4 4 2005−04−20 0 7 : 4 5 s i g s b e e 2 b s t r a t i g r a p h y i n d e x . j p g
1 6 1 4 9 4 4 4 2005−04−20 0 7 : 4 5 s i g s b e e 2 b r e f l e c t i o n c o e f f i c i e n t s . s e g y
3 0 0 0 4 0 2 2005−04−20 0 7 : 4 5 z o f f . hh
3 1 5 6 0 9 2005−04−20 0 7 : 4 5 s i g s b e e 2 b z e r o o f f s e t n f s . j p g
3 1 4 9 8 3 2005−04−20 0 7 : 4 5 s i g s b e e 2 b z e r o o f f s e t m p . j p g
3 6 5 9 0 1 2005−04−20 0 7 : 4 5 s i g s b e e 2 b z e r o o f f s e t f s . j p g
1 6 1 4 9 4 4 4 2005−04−20 0 7 : 4 5 s i g s b e e 2 b s t r a t i g r a p h y . s e g y
1 6 9 1 2 0 5 4 1 2005−06−10 0 3 : 4 2 S R C 0 t s p a r s e . hh
8 4 5 6 0 5 7 1 2005−06−10 0 3 : 4 2 S R C 0 x s p a r s e . hh
8 4 5 6 0 5 7 1 2005−06−10 0 3 : 4 4 SRC0x . hh
8 4 5 6 0 5 7 1 2005−06−10 0 3 : 4 4 SRC1x . hh
8 4 5 6 0 5 7 1 2005−06−10 0 3 : 4 4 SRC2x . hh
1 6 9 1 2 0 5 4 1 2005−06−10 0 3 : 4 4 SRC0t . hh
1 6 9 1 2 0 5 4 1 2005−06−10 0 3 : 4 5 SRC1t . hh
1 6 9 1 2 0 5 4 1 2005−06−10 0 3 : 4 6 SRC2t . hh
Table 1: List of all available files in the Madagascar Sigsbee2 repository
The Sigsbee2 models found in the Madagascar repository share the same dimensions
and sampling rate. The model is 9.144 km (30 000 ft) in depth and 24.384 km (80 000 ft) in
length. All the models contain 7.62 m (25 ft) grid spacing except for the migrated models
that have 11.43 m (37.5 ft) lateral grid spacing. Throughout this article both standard and
metric units will be presented in tabular form but all figures will exclusively utilize metric
units.
Table 2 displays the correct values that Sigsbee2 model headers should contain.
Sigsbee 2A Models
The Sigsbee2A velocity and reflection coefficient models are easily viewed using Madagascar.
There are 2 velocity models, a smooth migrated model and a true stratigraphic model. The
SCons script sigsbee/model2A/SConstruct contains a set of rules that tell Madagascar to
fetch the data append the headers and make several plots. This script is reproduced in
Table 3.
Typing Command 1 within the sigsbee/model2A directory runs the script.
bash-3.1$ scons view
(1)
The Sigsbee2A migrated and stratigraphic velocity models are shown in Figures 1a
and 1b respectively. A plot of the reflection coefficients are shown in Figure 1c.
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Stratigraphic Models
Standard Units
n1=1201
n2=3201
Metric Units
n1=1201
n2=3201
Migrated Models
Standard Units
n1=1201
n2=2133
Metric Units
n1=1201
n2=2133
d1=25
d2=25
o1=0
o2=10000
label1=Depth
label2=Distance
unit1=ft
unit2=ft
d1=.00762
d2=.00762
o1=0
o2=3.048
label1=Depth
label2=Distance
unit1=km
unit2=km
d1=25
d2=37.5
o1=0
o2=10025
label1=Depth
label2=Distance
unit1=ft
unit2=ft
d1=.00762
d2=.0143
o1=0
o2=3.055
label1=Depth
label2=Distance
unit1=km
unit2=km
Table 2: Header information for Sigsbee2 models, note the initial offset in the horizontal
direction and the coarse lateral sampling of the migrated models.
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from r s f . p r o j import ∗
#######################################
# S i g s b e e 2A v e l o c i t y m o d e l c o n s t r u c t #
#######################################
PRFX = ’ s i g s b e e 2 a
SUFX = ’ . s g y ’
’
for c in ( ’ m i g r a t i o n v e l o c i t y ’ , ’ s t r a t i g r a p h y ’ , ’ r e f l e c t i o n c o e f f i c i e n t s ’ ) :
i f ( c== ’ m i g r a t i o n v e l o c i t y ’ ) :
v= ’ vmig2A ’
o =3.055
d =.01143
s =.0003048
l= ’ M i g r a t i o n \ V e l o c i t y ’
a= ’ y ’
u= ’km/ s ’
i f ( c== ’ s t r a t i g r a p h y ’ ) :
v= ’ v s t r 2 A ’
o =3.048
d =.00762
s =.0003048
l= ’ S t r a t i g r a p h i c \ V e l o c i t y ’
a= ’ y ’
u= ’km/ s ’
i f ( c== ’ r e f l e c t i o n c o e f f i c i e n t s ’ ) :
v= ’ r e f l e c t i o n C o e f f i c i e n t s ’
o =3.048
d =.00762
s=1
l= ’ R e f l e c t i o n \ C o e f f i c i e n t s ’
a= ’ n ’
u= ’ ’
h = c + ’ head ’
t = PRFX + c + SUFX
Fetch ( t , ’ s i g s b e e ’ )
Flow ( [ v , h ] , t ,
’’’
s e g y r e a d t f i l e =$ {TARGETS[ 1 ] } |
put
o1=0 d1 =.00762
l a b e l 1=Depth
o2=%f d2=%f
l a b e l 2=D i s t a n c e
| s c a l e r s c a l e=%f
’ ’ ’ %(o , d , s ) )
u n i t 1=km
u n i t 2=km
R e s u l t ( v , v , ’ ’ ’ window f 1 =1 | g r e y c o l o r=i s c a l e b a r=y a l l p o s=%s s c r e e n r a t i o =.375 s c r e e n h t =3 b a r r e v e r s e=y
w h e r e t i t l e=t t i t l e=%s l a b e l s z =4 t i t l e s z =6 b a r l a b e l=V e l o c i t y b a r u n i t=%s ’ ’ ’ % ( a , l , u ) )
End ( )
Table 3: Contents of model2A/SConstruct script.
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a
b
c
Figure 1: Sigsbee 2A contains a stratigraphic velocity model (a) a migrated smoothed model
(b) and a reflection coefficient model (c).
Sigsbee 2B Models
The Sigsbee 2B model contains the same general geometry as the 2A model except for a
more realistic water to floor boundary which results in multiple generation when shots are
modeled on it. However, dealing with the files is basically identical the headers should also
be calibrated as shown in Table 2.
Table 4 shows the contents of the sigsbee/model2b/SConstruct script. This file is quite
similar to the one found in the Sigsbee 2A section and contains a list of rules that fetch the
datasets and plot them.
Typing Command 2 within the sigsbee/model2B directory runs the script.
bash-3.1$ scons view
(2)
A plot of the migrated velocity model is shown below Figure 2b while the stratigraphic
model can be seen in Figure 2a. A plot of the reflection coefficients are shown in Figure 2c.
SHOT RECORDS
Several sets of data were acquired on the Sigsbee models. The Madagascar repository
contains one survey taken on the Sigsbee2A model which was performed with an absorbing
surface boundary condition. Two surveys were conducted on the Sigsbee2B models one
with a free surface boundary and one without.
The three surveys shared the same acquisition geometry. Each receiver recorded data
every .008 seconds for 1 500 timesteps resulting in 12 seconds of data. A 7 950 m (26 100
ft) long streamer cable was deployed with 348 hydrophones spaced 22.86 m (75 ft) apart.
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from r s f . p r o j import ∗
#######################################
# S i g s b e e 2B v e l o c i t y m o d e l c o n s t r u c t #
#######################################
PRFX = ’ s i g s b e e 2 b
SUFX = ’ . s e g y ’
’
for c in ( ’ m i g r a t i o n v e l o c i t y ’ , ’ s t r a t i g r a p h y ’ , ’ r e f l e c t i o n c o e f f i c i e n t s ’ ) :
i f ( c== ’ m i g r a t i o n v e l o c i t y ’ ) :
v= ’ vmig2B ’
o =3.055
d =.0143
s =.0003048
l= ’ M i g r a t i o n \ V e l o c i t y ’
a= ’ y ’
u= ’ \ (km\/ s \ ) ’
i f ( c== ’ s t r a t i g r a p h y ’ ) :
v= ’ v s t r 2 B ’
o =3.048
d =.00762
s =.0003048
l= ’ S t r a t i g r a p h i c \ V e l o c i t y ’
a= ’ y ’
u= ’ \ (km\/ s \ ) ’
i f ( c== ’ r e f l e c t i o n c o e f f i c i e n t s ’ ) :
v= ’ r e f l e c t i o n C o e f f i c i e n t s 2 B ’
o =3.048
d =.00762
s=1
l= ’ R e f l e c t i o n \ C o e f f i c i e n t s ’
a= ’ n ’
u= ’ ’
h = c + ’ head ’
t = PRFX + c + SUFX
Fetch ( t , ’ s i g s b e e ’ )
Flow ( [ v , h ] , t ,
’’’
s e g y r e a d t a p e=$SOURCE t f i l e =$ {TARGETS[ 1 ] } |
put
o1=0 d1 =.00762
l a b e l 1=Depth
u n i t 1=km
o2=%f d2=%f
l a b e l 2=D i s t a n c e u n i t 2=km
| s c a l e r s c a l e=%f
’ ’ ’ %(o , d , s ) , s t d i n =0)
R e s u l t ( v , v , ’ ’ ’ g r e y c o l o r=i
w h e r e t i t l e=t
s c a l e b a r=y a l l p o s=%s s c r e e n r a t i o =.375 s c r e e n h t =3
t i t l e=%s l a b e l s z =4 t i t l e s z =6 b a r l a b e l=%s ’ ’ ’ % ( a , l , u ) )
End ( )
Table 4: Contents of model2B/SConstruct script.
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a
b
c
Figure 2: Sigsbee 2B contains two velocity models, a stratigraphic model (a) and a migrated
model(b). The resulting reflection coefficients are shown in (c).
Shots were fired every 45.72 m (150 ft) starting at 3 330 m (10 925 ft). Table 5 shows the
values that Sigsbee shot headers should contain.
Standard
n1=1500
n2=348
n3=500 or 496
Metric
n1=1500
n2=348
n3=500 or 496
d1=0.008
d2=75
d3=150
o1=0
o2=0
o3=10925
label1=Time
label2=Offset
label3=Shot-Coord
unit1=s
unit2=ft
unit3=ft
d1=0.008
d2=.02286
d3=.04572
o1=0
o2=0
o3=3.330
label1=Time
label2=Offset
label3=Shot-Coord
unit1=s
unit2=km
unit3=km
Table 5: Appropriate header values for Sigsbee shot records. The number of shots; n3,
varies slightly between the surveys
Sigsbee 2A shot records
The survey performed on the Sigsbee2A model had an infinite surface boundary condition.
The script found at data2A/SConstruct whose contents are displayed in Table 6 generates
a Madagascar formatted data file shots.rsf and also produces several shot images.
Typing Command 3 within the sigsbee/data2A directory runs the script.
bash-3.1$ scons view
(3)
A plot of the 70th shot, made 6.5 km in to the model is produced by the SConstruct
script and is shown below in Figure 3 The zero offset data is presented in Figure 4.
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############################
#
S i g s b e e 2A S h o t Data
#
############################
from r s f . p r o j import ∗
#−−−−−−− D e f i n e V a r i a b l e s and F i l e n a m e s −−−−−−#
data = ’ s i g s b e e 2 a n f s . sgy ’
#−−−−−−−−−−−−− I m p o r t Data −−−−−−−−−−−−−−−−−−−#
#−− U s e s f t p p r o g r a m F e t c h
Fetch ( data , ’ s i g s b e e ’ )
#−−−−−−−−−− C o n v e r t Data −−−−−−−−−−−−−−−−−−−−#
Flow ( ’ z d a t a t z d a t a . / dhead . / bdhead ’ , data ,
’’’
segyread
t f i l e =$ {TARGETS[ 1 ] }
h f i l e =$ {TARGETS[ 2 ] }
b f i l e =$ {TARGETS[ 3 ] }
’ ’ ’)
# create
sraw ( t , o , s ) :
o= f u l l
offset ,
s=s h o t
position ,
t=t i m e
’ s s ’ , ’ t z d a t a ’ , ’ dd t y p e= f l o a t | headermath o u t p u t =”10925+ f l d r ∗150” | window ’ )
’ oo ’ , ’ t z d a t a ’ , ’ dd t y p e= f l o a t | headermath o u t p u t=” o f f s e t ”
| window ’ )
’ s i ’ , ’ s s ’ , ’ math o u t p u t=i n p u t /150 ’ )
’ o i ’ , ’ oo ’ , ’ math o u t p u t=i n p u t /75 ’ )
’ o s ’ , ’ o i s i ’ , ’ c a t a x i s =2 s p a c e=n $ {SOURCES [ 1 ] } | t r a n s p | dd t y p e=i n t ’ )
’ sraw ’ , ’ z d a t a o s ’ ,
’’’
i n t b i n head=$ {SOURCES [ 1 ] } xkey=0 ykey=1
’ ’ ’)
Flow ( ’ s h o t ’ , ’ sraw ’ ,
’’’
put
l a b e l 1=Time
u n i t 1=s
d2 =.02286 o3=0
l a b e l 2=O f f s e t
u n i t 2=km
d3 =.04572 o3 =3.330 l a b e l 3=Shot−c o o r d u n i t 3=km |
m u t t e r h a l f= f a l s e t 0 =1.0 v0 =6000
’ ’ ’)
Flow (
Flow (
Flow (
Flow (
Flow (
Flow (
#−−−−−−−−−−−−−−−− P l o t Data −−−−−−−−−−−−−−−#
Result ( ’ zero ’ , ’ shot ’ ,
’’’
window
min2=0 max2=0 s i z e 2 =1 |
grey
p c l i p =98 c o l o r=I s c r e e n r a t i o =1.5 g a i n p a n e l=a
l a b e l 2=P o s i t i o n l a b e l 1=Time t i t l e = l a b e l 3=
u n i t 2=km u n i t 1=s
l a b e l s z =3
’ ’ ’)
Result ( ’ shot70 ’ , ’ shot ’ ,
’’’
window n3=1 f 3 =70 |
grey
p c l i p =99 c o l o r=I g a i n p a n e l=a wantframenum=y
u n i t 1=s
l a b e l 2=O f f s e t u n i t 2=km l a b e l 3=Shot u n i t 3=km t i t l e =
s c r e e n r a t i o =1.35 l a b e l s z =3
’ ’ ’)
End ( )
l a b e l 1=Time
Table 6: Contents of data2A/SConstruct script.
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Figure 3: Snapshot of shot number 70 performed on sigsbee 2A the position of the source
in km is in the lower left hand corner of the plot.
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Figure 4: Sigsbee2A zero offset data
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Sigsbee 2B Shot Records
The Sigsbee 2B library contains two sets of shot data, nfs and fs. These shots were modeled
with free and non free surface boundary conditions.
Free surface model
A SConstruct script found at sigsbee/data2B/fs/ is presented in Table 7. This script reads
the segy source file and converts it to Madagascar’s RSF format and appends the header
as necessary. The free surface boundary present within this model allows for the generation
of reflections at the model edges.
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#######################################
# S i g s b e e 2B F r e e S u r f a c e S h o t Data
#
#######################################
from r s f . p r o j import ∗
#−−−−−−− D e f i n e V a r i a b l e s and F i l e n a m e s −−−−−−#
data = ’ s i g s b e e 2 b f s . segy ’
#−−−−−−−−−−−−− I m p o r t Data −−−−−−−−−−−−−−−−−−−#
#−− U s e s f t p p r o g r a m F e t c h
Fetch ( data , ’ s i g s b e e ’ )
#−−−−−−−−−− C o n v e r t Data −−−−−−−−−−−−−−−−−−−−#
Flow ( ’ z d a t a t z d a t a . / dhead . / bdhead ’ , data ,
’’’
segyread
t a p e=$SOURCE
t f i l e =$ {TARGETS[ 1 ] }
h f i l e =$ {TARGETS[ 2 ] }
b f i l e =$ {TARGETS[ 3 ] }
’ ’ ’ , s t d i n =0)
# create
sraw ( t , o , s ) :
o= f u l l
offset ,
s=s h o t
position ,
t=t i m e
’ s s ’ , ’ t z d a t a ’ , ’ dd t y p e= f l o a t | headermath o u t p u t =”10925+ f l d r ∗150” | window ’ )
’ oo ’ , ’ t z d a t a ’ , ’ dd t y p e= f l o a t | headermath o u t p u t=” o f f s e t ”
| window ’ )
’ s i ’ , ’ s s ’ , ’ math o u t p u t=i n p u t /150 ’ )
’ o i ’ , ’ oo ’ , ’ math o u t p u t=i n p u t /75 ’ )
’ o s ’ , ’ o i s i ’ , ’ c a t a x i s =2 s p a c e=n $ {SOURCES [ 1 ] } | t r a n s p | dd t y p e=i n t ’ )
’ sraw ’ , ’ z d a t a o s ’ ,
’’’
i n t b i n head=$ {SOURCES [ 1 ] } xkey=0 ykey=1
’ ’ ’)
Flow ( ’ shotFs2B ’ , ’ sraw ’ ,
’’’
put
l a b e l 1=Time
u n i t 1=s
d2 =.02286 o3=0
l a b e l 2=O f f s e t
u n i t 2=km
d3 =.04572 o3 =3.330 l a b e l 3=Shot−c o o r d u n i t 3=km |
m u t t e r h a l f= f a l s e t 0 =1.0 v0 =6000
’ ’ ’)
Flow (
Flow (
Flow (
Flow (
Flow (
Flow (
#−−−−−−−−−−−−−−−− P l o t Data −−−−−−−−−−−−−−−#
R e s u l t ( ’ z e r o 2 B f s ’ , ’ shotFs2B ’ , ’ ’ ’ window $SOURCE min2=0 max2=0 s i z e 2 =1
| grey
p c l i p =98 c o l o r=I s c r e e n r a t i o =1.5 g a i n p a n e l=a
l a b e l 2=P o s i t i o n l a b e l 1=Time t i t l e = l a b e l 3=
u n i t 2=km u n i t 1=s
l a b e l s z =3 ’ ’ ’ )
R e s u l t ( ’ s h o t 7 0 2 B f s ’ , ’ shotFs2B ’ , ’ ’ ’ window $SOURCE n3=1 f 3 =70 |
grey
p c l i p =99 c o l o r=I g a i n p a n e l=a wantframenum=y
u n i t 1=s
l a b e l 2=O f f s e t u n i t 2=km l a b e l 3=Shot u n i t 3=km t i t l e =
s c r e e n r a t i o =1.35 l a b e l s z =3 ’ ’ ’ )
l a b e l 1=Time
End ( )
Table 7: Contents of data2B/fs/SConstruct script.
Again shot number 70, fired 6.5 km into the model, is plotted in Figure 5. The precise
11
coordinates of the shot are shown in the lower left hand corner of the figure. The zero offset
data is presented in Figure 6.
Infinite Surface Model
This data was prepared with the boundaries of the model extending forever; as such multiples are not created as a result of the model edges.
A SConsctuct script found at sigsbee/data2B/fs/ is presented in Table 8. This script
translates the segy source data file and converts it into rsf format.
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#########################
# S i g s b e e 2B S h o t Data #
#########################
from r s f . p r o j import ∗
#−−−−−−− D e f i n e V a r i a b l e s and F i l e n a m e s −−−−−−#
data = ’ s i g s b e e 2 b n f s . segy ’
#−−−−−−−−−−−−− I m p o r t Data −−−−−−−−−−−−−−−−−−−#
#−− U s e s f t p p r o g r a m F e t c h
Fetch ( data , ’ s i g s b e e ’ )
#−−−−−−−−−− C o n v e r t Data −−−−−−−−−−−−−−−−−−−−#
Flow ( ’ z d a t a t z d a t a . / dhead . / bdhead ’ , data ,
’’’
segyread
t a p e=$SOURCE
t f i l e =$ {TARGETS[ 1 ] }
h f i l e =$ {TARGETS[ 2 ] }
b f i l e =$ {TARGETS[ 3 ] }
’ ’ ’ , s t d i n =0)
# create
sraw ( t , o , s ) :
o= f u l l
offset ,
s=s h o t
position ,
t=t i m e
’ s s ’ , ’ t z d a t a ’ , ’ dd t y p e= f l o a t | headermath o u t p u t =”10925+ f l d r ∗150” | window ’ )
’ oo ’ , ’ t z d a t a ’ , ’ dd t y p e= f l o a t | headermath o u t p u t=” o f f s e t ”
| window ’ )
’ s i ’ , ’ s s ’ , ’ math o u t p u t=i n p u t /150 ’ )
’ o i ’ , ’ oo ’ , ’ math o u t p u t=i n p u t /75 ’ )
’ o s ’ , ’ o i s i ’ , ’ c a t a x i s =2 s p a c e=n $ {SOURCES [ 1 ] } | t r a n s p | dd t y p e=i n t ’ )
’ sraw ’ , ’ z d a t a o s ’ ,
’’’
i n t b i n head=$ {SOURCES [ 1 ] } xkey=0 ykey=1
’ ’ ’)
Flow ( ’ s h o t N f s 2 B ’ , ’ sraw ’ ,
’’’
put
l a b e l 1=Time
u n i t 1=s
d2 =.02286 o3=0
l a b e l 2=O f f s e t
u n i t 2=km
d3 =.04572 o3 =3.330 l a b e l 3=Shot−c o o r d u n i t 3=km |
m u t t e r h a l f= f a l s e t 0 =1.0 v0 =6000
’ ’ ’)
Flow (
Flow (
Flow (
Flow (
Flow (
Flow (
#−−−−−−−−−−−−−−−− P l o t Data −−−−−−−−−−−−−−−#
R e s u l t ( ’ z e r o 2 B n f s ’ , ’ s h o t N f s 2 B ’ , ’ ’ ’ window $SOURCE min2=0 max2=0 s i z e 2 =1
| grey
p c l i p =98 c o l o r=I s c r e e n r a t i o =1.5 g a i n p a n e l=a
l a b e l 2=P o s i t i o n l a b e l 1=Time t i t l e = l a b e l 3=
u n i t 2=km u n i t 1=s
l a b e l s z =3 ’ ’ ’ )
R e s u l t ( ’ s h o t 7 0 2 B n f s ’ , ’ s h o t N f s 2 B ’ , ’ ’ ’ window $SOURCE n3=1 f 3 =70 |
grey
p c l i p =99 c o l o r=I g a i n p a n e l=a wantframenum=y
u n i t 1=s l a b e l 1=Time
l a b e l 2=O f f s e t u n i t 2=km l a b e l 3=Shot u n i t 3=km t i t l e =
s c r e e n r a t i o =1.35 l a b e l s z =3 ’ ’ ’ )
End ( )
Table 8: Contents of data2B/nfs/SConstruct script.
Similar plots are produced for this model. Figure 7 shows an image of shot number 70
taken at 6.5 km into the model. Figure 8 displays the zero offset data acquired on this
model.
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Figure 5: Shot number 70 performed on sigsbee 2B FS model. The shot location is presented
in the lower left hand corner of the plot
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Figure 6: Sigsbee2B free surface boundary zero offset data.
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Figure 7: Shot 70 performed in Sigsbee 2B NFS model.
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Figure 8: Sigsbee 2B reflecting surface zero offset data, notice the decreased multiples from
the free surface model
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FINITE DIFFERENCE MODELING
Finite difference (FD) shot and data modeling can be performed on the Sigsbee models
using Madagascar. This example will use the Sigsbee2A model but but it could be easily
extended to perform modeling on Sigsbee2B.
For the purposes of this example a shot will be fired at 10 km along the horizontal
coordinate and at a depth of 10 meters. Receivers are spread at a depth of 0 meters every
7.62 m (25 ft) along the entire scope of the model. This long receiver cable is impractical
but useful for these purposes. Data is recorded on every receiver at time increments of 1
ms 3000 times resulting in 3 seconds of data.
An SConstruct file located within sigsbee/fdmod2A/ properly formats the model and
inputs necessary parameters to perform a shot on the Sigsbee model. This file is reproduced
below in Table 9.
Typing Command 4 within the sigsbee/fdmod2A/ directory runs the FD modeling script.
bash-3.1$ scons view
(4)
This script first constructs the survey acquisition geometry as was previously mentioned.
An image of the survey is created and presented in Figure 9.
Figure 9: FD model geometry as performed on the Sigsbee 2A velocity model. The X
represents the shot while the smaller * symbols represent receivers. The receivers extent
along the right hand side although it is not clear in this image.
Firing the shot results the propagation of a wavefield which can be seen in the movie
wfl.vpl that is generated. Typing Command 5 within the sigsbee/fdmod2A directory displays
the wavefield movie.
bash-3.1$ scons wfl.vpl
(5)
Four frames from this movie are presented in Figure 10 illustrating the propagation of
the wavefield in the model.
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from r s f . p r o j import ∗
import fdmod
##
# S i g s b e e 2A
##
d a t a= ’ s i g s b e e 2 a s t r a t i g r a p h y . s g y ’
F e t c h ( data , ’ s i g s b e e ’ )
Flow ( [ ’ v s t r 2 A ’ , ’ v s t r 2 A h e a d ’ ] , data ,
’’’
s e g y r e a d t a p e=$SOURCE t f i l e =$ {TARGETS[ 1 ] } |
put
o1=0 d1=25
l a b e l 1=z u n i t 1=f t
o2 =10000 d2=25
l a b e l 2=x u n i t 2=f t
’ ’ ’ , s t d i n =0)
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
par = {
’ nt ’ : 7 0 0 0 , ’ dt ’ : 0 . 0 0 1 , ’ ot ’ : 0 ,
’ l t ’ : ’ t ’ , ’ ut ’ : ’ s ’ ,
’ kt ’ : 1 0 0 ,
# wavelet delay
’ nx ’ : 3 2 0 1 , ’ ox ’ : 0 , ’ dx ’ : 0 . 0 0 7 6 2 , ’ l x ’ : ’ x ’ , ’ ux ’ : ’km ’ ,
’ nz ’ : 1 2 0 1 , ’ o z ’ : 0 , ’ dz ’ : 0 . 0 0 7 6 2 , ’ l z ’ : ’ z ’ , ’ uz ’ : ’km ’ ,
}
# add F−D m o d e l i n g p a r a m e t e r s
fdmod . param ( p a r )
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# wavelet
Flow ( ’ wav ’ , None ,
’’’
s p i k e nsp=1 mag=1 n1=%(n t ) d d1=%(d t ) g o1=%(o t ) g k1=%(k t ) d |
r i c k e r 1 f r e q u e n c y =15 |
s c a l e a x i s =123 |
put l a b e l 1=t l a b e l 2=x l a b e l 3=y |
transp
’ ’ ’ % par )
R e s u l t ( ’ wav ’ ,
’ t r a n s p | window n1=200 | g r a p h t i t l e =”” l a b e l 1 =”t ” l a b e l 2= u n i t 2= ’ )
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# experiment setup
Flow ( ’ r ’ , None , ’ math n1=%(nx ) d d1=%(dx ) g o1=%(ox ) g o u t p u t=0 ’ % p a r )
Flow ( ’ s ’ , None , ’ math n1=1
d1=0
o1=0
o u t p u t=0 ’ % p a r )
# receiver positions
Flow ( ’ z r ’ , ’ r ’ , ’ math o u t p u t =”0” ’ )
Flow ( ’ x r ’ , ’ r ’ , ’ math o u t p u t=”x1 ” ’ )
Flow ( ’ r r ’ , [ ’ x r ’ , ’ z r ’ ] ,
’’’
c a t a x i s =2 s p a c e=n
$ {SOURCES [ 0 ] } $ {SOURCES [ 1 ] } | t r a n s p
’ ’ ’ , s t d i n =0)
P l o t ( ’ r r ’ , fdmod . r r p l o t ( ’ ’ , p a r ) )
# source p o s i t i o n s
Flow ( ’ z s ’ , ’ s ’ , ’ math o u t p u t =.01 ’ )
Flow ( ’ x s ’ , ’ s ’ , ’ math o u t p u t =10.0 ’ )
Flow ( ’ r s ’ , ’ s ’ , ’ math o u t p u t=1 ’ )
Flow ( ’ s s ’ , [ ’ x s ’ , ’ z s ’ , ’ r s ’ ] ,
’’’
c a t a x i s =2 s p a c e=n
$ {SOURCES [ 0 ] } $ {SOURCES [ 1 ] } $ {SOURCES [ 2 ] } | t r a n s p
’ ’ ’ , s t d i n =0)
P l o t ( ’ s s ’ , fdmod . s s p l o t ( ’ ’ , p a r ) )
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# Velocity
Flow ( ’ v e l ’ , ’ v s t r 2 A ’ ,
’’’
s c a l e r s c a l e =.0003048 |
put o1=%(o z ) g d1=%(dz ) g
’ ’ ’ % par )
o2=%(o z ) g d2=%(dz ) g
P l o t ( ’ v e l ’ , fdmod . c g r e y ( ’ ’ ’
a l l p o s=y b i a s =1.5 p c l i p =100 c o l o r=j t i t l e =S u r v e y \ D e s i g n
’ ’ ’ , par ) )
Result ( ’ v e l ’ , [ ’ v e l ’ , ’ r r ’ , ’ s s ’ ] , ’ Overlay ’ )
l a b e l s z =4 t i t l e s z =6 w h e r e t i t l e=t
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# density
Flow ( ’ den ’ , ’ v e l ’ , ’ math o u t p u t=1 ’ )
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# f i n i t e −d i f f e r e n c e s m o d e l i n g
fdmod . awefd ( ’ d a t ’ , ’ w f l ’ , ’ wav ’ , ’ v e l ’ , ’ den ’ , ’ s s ’ , ’ r r ’ , ’ f r e e=y d e n s=y ’ , p a r )
P l o t ( ’ w f l ’ , fdmod . wgrey ( ’ p c l i p =99 t i t l e =W a v e f i e l d \ Movie l a b e l s z =4 t i t l e s z =6 w h e r e t i t l e=t ’ , p a r ) , v i e w =1)
t i m e s =[ ’ 1 ’ , ’ 2 ’ , ’ 3 ’ , ’ 4 ’ ]
c n t r =0
f o r i t e m i n [ ’ 9 ’ , ’ 19 ’ , ’ 29 ’ , ’ 39 ’ ] :
R e s u l t ( ’ t i m e ’+item , ’ w f l ’ ,
’’’
window f 3=%s n3=1 min1=0 min2=0 | g r e y g a i n p a n e l=a
p c l i p =99 wantframenum=y t i t l e =W a v e f i e l d \ a t \ %s \ s l a b e l s z =4
t i t l e s z =6 s c r e e n r a t i o =.375 s c r e e n h t =2 w h e r e t i t l e=t
l a b e l 1=z l a b e l 2=x u n i t 1=k f t u n i t 2=k f t
’ ’ ’ % ( item , t i m e s [ c n t r ] ) )
cntr = cntr + 1
R e s u l t ( ’ d a t ’ , ’ window j 2 =4 j 1 =2 | t r a n s p | ’ + fdmod . d g r e y ( ’ p c l i p =99 ’ , p a r ) )
End ( )
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a
b
c
d
Figure 10: Images of the propagating wavefield in the Sigsbee model generated by a finite
difference model.
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The resulting data is then presented in the file dat.vpl. This plot is reproduced here in
Figure 11.
Figure 11: Data gathered by the receivers in the FD model survey.
FD models can be performed on the Sigsbee2B model in a similar fashion. The primary
change would be in appending line six, the model input file, in the SConstruct file shown
in Table 9.