Post on 23-Jan-2016
description
Salt Flank Imaging by PS Interferometry
Xiang Xiao
Univ. of Utah
Feb. 3
Outline
I. Motivation
II. Theory
III. Numerical Tests
IV. Field Data Examples
V. Conclusion
Outline
I. Motivation
II. Theory
III. Numerical Tests
IV. Field Data Examples
V. Conclusion
I. Motivation
• Goal:– Salt Flank Imaging with Migration of PS Transmission Waves;
• Method:
– Standard Migration (KM);
– Reduced-time Migration (RM), Sheley and Schuster, 2003;
– Interferometric Migration (IM), and Interferometric Redatuming (IR), Schuster, 2004;
Outline
I. Motivation
II. Theory
III. Numerical Tests
IV. Field Data Examples
V. Conclusion
Uninteresting PartUninteresting Part of Mediumof Medium
Tim
eT
ime
Goal: Image Interface by PS Transmitted WavesGoal: Image Interface by PS Transmitted Waves
MM gg
ss
PP
d(M|d(M|ss)) d(g|s)d(g|s)
PPPPPPSS
d(M|d(M|ss)) d(g|s)*d(g|s)*((gg,,MM) =) =
m(m(xx)=)=
== e e eei wi w t + t + i wi w tt -i w-i w t - t - i wi w tt
PPSS PPPP
== e ei wi w ((t t –– tt))
Uninteresting PartUninteresting Part of Mediumof Medium
Tim
eT
ime
Goal: Image Interface by PS Transmitted WavesGoal: Image Interface by PS Transmitted Waves
MM gg
ss
PP
d(M|d(M|ss)) d(g|s)d(g|s)
PPPPPPSS
ss
d(M|d(M|ss)) d(g|s)*d(g|s)*((gg,,MM) = ) =
m(m(xx)=)=
Uninteresting PartUninteresting Part of Mediumof Medium
Tim
eT
ime
Goal: Image Interface by PS Transmitted WavesGoal: Image Interface by PS Transmitted Waves
MM gg
ss
PP
d(M|d(M|ss)) d(g|s)d(g|s)
PPPPPPSS
ss
d(M|d(M|ss)) d(g|s)*d(g|s)*((gg,,MM) = ) =
m(m(xx)=)=
Uninteresting PartUninteresting Part of Mediumof Medium
Tim
eT
ime
Goal: Image Interface by PS Transmitted WavesGoal: Image Interface by PS Transmitted Waves
MM gg
ss
PP
d(M|d(M|ss)) d(g|s)d(g|s)
PPPPPPSS
ss
d(M|d(M|ss)) d(g|s)*d(g|s)*((gg,,MM) = ) =
m(m(xx)=)=
Unique Specular Point Snell’s Law OKUnique Specular Point Snell’s Law OK
g,g,MM
((gg,,MM) ) m(x) =m(x) = eei wi w ((t t –– tt))––
xx xx
xxDatuming
Migration
Interferometric Interferometric PSPS Datuming Datuming
g,g,MM
((gg,,MM) ) m(x) =m(x) = eei wi w ((t t –– tt))––
xx xx
Eliminates src/rec statics and Eliminates src/rec statics and uninteresting parts of the medium.uninteresting parts of the medium.
Raise buried src to Raise buried src to interestinginteresting inter. inter.
Outline
I. Motivation
II. Theory
III. Numerical Tests
IV. Field Data Examples
V. Conclusion
Salt Velocity ModelSalt S-wave Velocity ModelSalt P-wave Velocity Model
Dep
th
(m)
X (m)X (m) m/s m/s
III. Numerical test
P-to-S ratios = 30.5
0
12000 1200
4400
20000 1200
2540
1170
VSP Gathers
Time (s)
PS Waves Shot @ (0,0)
Time (s)
P Wave Shot @ (0,0)
Dep
th
(m)
III. Numerical test
Interferometric Interferometric PSPS Datuming Datuming
g,g,MM
((gg,,MM) ) m(x) =m(x) = eei wi w ((t t –– tt))––
xx xx
Eliminates src/rec statics and Eliminates src/rec statics and uninteresting parts of the medium.uninteresting parts of the medium.
Raise buried src to Raise buried src to interestinginteresting inter. inter.
Synthetic vs. Redatuming Data
Time (s)
Virtual after IR
Time (s)
Synthetic PS VSP
Dep
th
(m)
III. Numerical test
KM vs. IM with Correct Velocity Model
IMKM
Dep
th
(m)
X (m)X (m)
III. Numerical test
0
12000 1200
963
13130 1200
7E4
-8E4
KM, RM vs. IM
Constant Static Shift in Data
Each Trace Advances 60 ms
III. Numerical test
KMD
epth
(m
)
X (m)
0
1200
0 1200
400
-700
Haven’t been imagedBoundary is shifted
III. Numerical test
RMD
epth
(m
)
X (m)
0
1200
0 1200
850
-950
Correctly imaged
Poor focused
III. Numerical test
IMD
epth
(m
)
X (m)
0
1200
0 1200
7E4
-8E4
Correctly imaged
Strong focused!Small cover of PS ray
Additionally imaged
III. Numerical test
ComparisonD
epth
(m
)
X (m)
0
1200
0 1200
KMRM
IM
III. Numerical test
Incorrect Migration Model
KM, RM vs. IM
90% Velocity Above Salt
III. Numerical test
KMD
epth
(m
)
X (m)
0
1200
0 1200
850
-1000
Correct place
Incorrectly imaged
III. Numerical test
RMD
epth
(m
)
X (m)
0
1200
0 1200
850
-1000
Incorrectly imaged,Should image as black
boundary
Correctly imaged
III. Numerical test
Elliptical artifacts
IMD
epth
(m
)
X (m)
0
1200
0 1200
4E4
-6E4
Correctly imaged
Correctly imaged!
III. Numerical test
Elliptical artifacts are removed
Comparison
KMRM
IM
Dep
th
(m)
X (m)
0
1200
0 1200
III. Numerical test
Outline
I. Motivation
II. Theory
III. Numerical Tests
IV. Field Data Examples
V. Conclusion
IV. Field Data
D
epth
(m
)
Offset (m)4878
0 1829
0
Well and Source Location
Source @150 m offset
P-to-S ratios = 2.7
Velocity ProfileS WaveP Wave
Dep
th
(m)
Velocity (m/s)
0
45000 5000 0 3000
2800 m
3200 m
Salt
IV. Field Data
Incorrect velocity model
P-to-S ratios = 1.6
150 X ComponentD
epth
(m
)
Traveltime (s)
2652
3887
1.2 3.0
Salt
Direct P
Reflect P
Alias (Reverberation)
IV. Field Data
Z ComponentD
epth
(m
)
Traveltime (s)
2652
3887
1.2 3.0
Salt
Direct P
Reflect P
Alias (Reverberation) Direct S
IV. Field Data
Processing Flow ChartOriginal Data
Reoriented
Pick desired events
Flatten, median filter, unflatten
Migration (KM, RM, IM)
Dep
th
(m)
Traveltime (s)
2652
3887
1.2 3.0
IV. Field Data
150 X Before Rotation
Dep
th
(m)
Traveltime (s)
2652
3887
1.2 3.0
IV. Field Data
150 X After RotationP wave energy was maximized
Dep
th
(m)
Traveltime (s)
2652
3887
1.2 3.0
III. Field Data
150 X PSS EventsTransmitted at upper boundary
150 X PPS EventsD
epth
(m
)
Traveltime (s)
2652
3887
1.2 3.0
III. Field Data
Transmitted at lower boundary
Migration of PSS
IV. Field Data
Ray Path Coverage
2000
4200
0 200
Dep
th
(m) SAL
T
Offset (m)
Migration of PSS
IV. Field Data
SALT
150 offset RM 150 offset IM
0 200 0 200Offset (m)
150 offset KM
2000
4200
0 200
Dep
th
(m)
Migration of PSS
IV. Field Data
SALT
Ray Path Coverage
2000
4200
0 200
Dep
th
(m)
Migration of PSS
IV. Field Data
SALT
Offset (m)
IV. Field Data
Migration of PPS
SALT
150 offset RM 150 offset IM
0 200 0 200
150 offset KM
2000
4200
0 200
Dep
th
(m)
Offset (m)
Migration of PPS
SALT
IV. Field Data
Outline
I. Motivation
II. Theory
III. Numerical Tests
IV. Field Data Examples
V. Conclusion
IV. Conclusion
• Benefits of IM:– Remove influence of static shifts and migration velocity
errors;
– Eliminated source statics by correlation;
– Remove elliptical artifacts, boost migration image contrast;
• Drawbacks of IM:– Migration artifacts from stationary phase approximation;
– Extra summations and computation time;
– Small range of incidence angle than true SWI data;
– Worse vertical resolution than KM;
Thank you!
• Thank the sponsor of the 2004 UTAM consortium for their support.