Transcript Slide 1

MS thesis
Salt Flank Delineation by
Interferometric Imaging of
Transmitted P-to-S Waves
Xiang Xiao
Advisor:
Gerard T. Schuster
Committee: Michael Zhdanov
Bob Smith
Cari Jonson
Univ. of Utah
Nov. 15
Outline
I.
II.
III.
IV.
V.
Motivation
Theory
Numerical Tests
Field Data Examples
Conclusion
Outline
I.
II.
III.
IV.
V.
Motivation
Theory
Numerical Tests
Field Data Examples
Conclusion
I. Motivation
• Goal:
– Salt Flank Imaging with Migration of
Transmitted P-to-S Waves;
• Method:
– Standard Migration (KM);
– Reduced-time Migration (RM), Sheley and
Schuster, 2003;
– Interferometric Migration (IM), and
Interferometric Redatuming (IR), Schuster,
2004;
Outline
I.
II.
III.
IV.
V.
Motivation
Theory
Numerical Tests
Field Data Examples
Conclusion
Goal: Image Interface by PS Transmitted Waves
Time
Uninteresting Part
of Medium
s
P
PS
M
d(M|s)
Standard Kirchhoff Migration:
X
PP
m(x) =
d(M|s) e
w,s,M
–
i w (t + t)
sx
xM
g
d(g|s)
Goal: Image Interface by PS Transmitted Waves
Time
Uninteresting Part
of Medium
s
P
PS
M
d(M|s)
Reduced-time migration:
X
m(x) =
d(M|s) e
–
i w (t + t + t)
sx
pick
t error =( t sx+ t xM)- ( t sx+
pick
pick
~( t sx+ t xg )- ( t sx+
error
g
d(g|s)
w,s,M
pick
xM
PP
t xM)
t xg )
Goal: Image Interface by PS Transmitted Waves
Time
Uninteresting Part
of Medium
s
P
PS
Interferometric migration:
M
d(M|s)
(g,M) = d(M|s) d(g|s)*
iwt+iwt
~e
PS
i w (t – t)
=e
e
-i w t - i w t
PP
PP
g
d(g|s)
Goal: Image Interface by PS Transmitted Waves
Time
Uninteresting Part
of Medium
s
P
d(M|s) d(g|s)*
(g,M) =
PS
M
d(M|s)
s
PP
g
d(g|s)
Goal: Image Interface by PS Transmitted Waves
Time
Uninteresting Part
of Medium
s
P
d(M|s) d(g|s)*
(g,M) =
PS
M
d(M|s)
s
PP
g
d(g|s)
Goal: Image Interface by PS Transmitted Waves
Time
Uninteresting Part
of Medium
s
Datuming
P
PS
d(M|s) d(g|s)*
(g,M) =
M
d(M|s)
s
X
Migration
– t)
(g,M) e – i w (t xM
xg
m(x) =
PP
g
d(g|s)
w,g,M
Unique Specular Point Snell’s Law OK
Interferometric PS Datuming


Eliminates src/rec statics and
uninteresting parts of the medium.
Move surface src to interesting inter.
(g,M) e
m(x) =
g,M
–
i w (t – t)
x x
Outline
I.
II.
III.
IV.
V.
Motivation
Theory
Numerical Tests
Field Data Examples
Conclusion
III. Numerical Tests
I. Rugose Lower Salt Boundary
II. Elastic Salt Model
III. Numerical test
Salt Velocity Model
Salt P-wave Velocity Model
Salt S-wave Velocity Model
2540
4400
Depth (m)
0
P-to-S ratios = 30.5
1170
2000
1200
0
X (m)
1200 m/s
0
X (m)
1200 m/s
III. Numerical test
VSP Gathers
PS Waves Shot @ (0,0)
Depth (m)
P Wave Shot @ (0,0)
Time (s)
Time (s)
Interferometric PS Datuming


Eliminates src/rec statics and
uninteresting parts of the medium.
Move surface src to interesting inter.
(g,M) e
m(x) =
g,M
–
i w (t – t)
x x
III. Numerical test
Synthetic vs. Redatuming Data
S-P Data from IR
Depth (m)
Synthetic S-P SWI Data
Time (s)
Time (s)
III. Numerical test
KM vs. IM
with Correct Velocity Model
KM
IM
963
7E4
Depth (m)
0
-8E4
1313
1200
0
X (m)
1200
0
X (m)
1200
III. Numerical test
KM, RM vs. IM
Constant Static Shift in Data
Each Trace Advances 8 ms
III. Numerical test
KM
400
Depth (m)
0
Incorrectly imaged
Boundary is shifted
1200
-700
0
X (m)
1200
III. Numerical test
RM
850
Depth (m)
0
Correctly imaged
Poor focused
1200
-950
0
X (m)
1200
III. Numerical test
IM
Additionally imaged
7E4
Depth (m)
0
Correctly imaged
Small cover
of PS ray
Strong focused!
-8E4
1200
0
X (m)
1200
III. Numerical test
Comparison
Depth (m)
0
KM
RM
IM
1200
0
X (m)
1200
III. Numerical test
KM, RM vs. IM
Incorrect Migration Model
90% Velocity Above Salt
III. Numerical test
KM
0
850
Depth (m)
Incorrectly imaged
Correct place
1200
-1000
0
X (m)
1200
III. Numerical test
RM
850
Depth (m)
0
Correctly imaged
Incorrectly imaged,
Should image as black boundary
Elliptical artifacts
1200
-1000
0
X (m)
1200
III. Numerical test
IM
4E4
Depth (m)
0
Correctly imaged
Correctly imaged!
Elliptical artifacts are removed
-6E4
1200
0
X (m)
1200
III. Numerical test
Comparison
Depth (m)
0
KM
RM
IM
1200
0
X (m)
1200
II. Elastic Salt Model
P-wave velocity model
Velocity (m/s)
0
Depth (m)
4500
Gas target lower boundary
11000
1500
0
X (m)
16000
a) P-wave velocity model
0
b) S-wave velocity model
Depth (m)
Depth (m)
0
11000
11000
0
X (m)
16000
0
0
0
Time (s)
12
12
0
Shot number
16000
d) CRG 1 Z-component
Time (s)
c) CRG 1 X-component
X (m)
319
0
Shot number
319
a) Ray tracing: direct P
b) Ray tracing: PPS events
0
Depth (km)
Depth (km)
0
11
11
0
X (km)
16
c) Ray tracing: PSS events
Depth (km)
0
11
0
X (km)
16
0
X (km)
16
a) PP Standard Migration
0
b) PS Standard Migration
Depth (m)
Depth (m)
0
11000
11000
0
X (m)
16000
0
c) Zoom View of PS KM
16000
d) Zoom View of PS IM
5000
Depth (m)
Depth (m)
5000
8000
6900
X (m)
X (m)
8700
8000
6900
X (m)
8700
PS interferometric migration
0
PS IM
Depth (m)
3000
6000
Correctly imaged!
9000
0
8000
X (m)
16000
Outline
I.
II.
III.
IV.
V.
Motivation
Theory
Numerical Tests
Field Data Examples
Conclusion
IV. Field Data
Well and Source Location
Source @150 m offset
Depth (m)
0
4878
0
Offset (m)
1829
IV. Field Data
Velocity Profile
S Wave
P Wave
0
Depth (m)
Incorrect
velocity model
P-to-S ratios = 2.7
2800 m
Salt
P-to-S ratios = 1.6
3200 m
4500
0
5000
0
Velocity (m/s)
5000
IV. Field Data
150 Z Component
2652
Reflect P
Depth (m)
Salt
Alias (Reverberation)
Direct P
3887
1.2
Traveltime (s)
3.0
IV. Field Data
150 X Component
2652
Reflect P
Depth (m)
Salt
Direct S
Alias (Reverberation)
Direct P
3887
1.2
Traveltime (s)
3.0
Processing Flow Chart
Original Data
Reoriented
Pick desired events
Flatten, median filter, unflatten
Migration (KM, RM, IM)
IV. Field Data
150 X Before Rotation
Depth (m)
2652
3887
1.2
Traveltime (s)
3.0
IV. Field Data
150 X After Rotation
P wave energy was maximized
Depth (m)
2652
3887
1.2
Traveltime (s)
3.0
III. Field Data
150 X PSS Events
Transmitted at upper boundary
Depth (m)
2652
3887
1.2
Traveltime (s)
3.0
III. Field Data
150 X PPS Events
Transmitted at lower boundary
Depth (m)
2652
3887
1.2
Traveltime (s)
3.0
IV. Field Data
Migration of PSS
Ray Path Coverage
Depth (m)
2000
SALT
4200
0
Offset (m)
200
IV. Field Data
Migration of PSS
150 offset KM
150 offset RM
150 offset IM
Depth (m)
2000
SALT
4200
0
200
0
Offset (m)
200
0
200
IV. Field Data
Migration of PPS
Ray Path Coverage
Depth (m)
2000
SALT
4200
0
Offset (m)
200
IV. Field Data
Migration of PPS
150 offset KM
150 offset RM
150 offset IM
Depth (m)
2000
SALT
4200
0
200
0
Offset (m)
200
0
200
Outline
I.
II.
III.
IV.
V.
Motivation
Theory
Numerical Tests
Field Data Examples
Conclusion
IV. Conclusion
• Advantage of PS transmission
migration
– it is capable of illuminating the boundary of
salt flanks above the receivers (and nearly
vertical boundaries if they exist).
IV. Conclusion
• Benefits of IM:
– Does not require knowledge of the overburden velocity;
– Remove influence of static shifts and/or migration velocity
errors;
– Eliminated source statics by correlation;
– Accurately image the salt boundary above the receivers;
• Drawbacks of IM:
– Migration artifacts due to violation of stationary phase
approximation;
– Extra summations and computation time;
– Small range of incidence angle than true SWI data;
– Worse spatial resolution than KM;
V. Future Work
• Pp/Ps reflection interferometric migration
• Anisotropy migration
– Try different VTI FD synthetic walkaway VSP data set;
– Apply it to a real data set;
• Preprocessing:
– Reorientation, separation, filtering, statics correction
• Postprocessing:
– Deconvolution
•
Potential application
– Kirchhoff multi arrival migration
– Subsalt imaging
– Interferometric tomography
Thanks to
• Jerry Schuster and my committee
members: Dr. Michael Zhdanov, Dr. Bob
smith, Dr. Cari Johnson for their advice
and constructive criticism;
• Scott Leaney and Hornby Brian for their
help on modeling;
Thanks to
• UTAM friends:
– Jianhua Yu for his help on Linux programming;
– Jianming Sheng and Min Zhou for their experiences
on interferometric imaging;
– Zhiyong Jiang and Ruiqing He for their help on
classes;
– Travis Crosby and all UTAM students for their
cheerful attitude; All UTAM sponsors for their support;
• Family
– My parents, brother and sister;
• Friends
– Liyun Ma, Huajian Yao, Zhaoyu Luo and Meiping
Tong, who encouraged me to continue on with my
research.
Questions?