Transcript 3D ANISTROPIC TRAVELTIME SOLVER

Primary-Only Imaging
Condition
Yue Wang
Outline
• Objective
• POIC Methodology
• Synthetic Data Tests
5-layer model
salt dome model
• Unocal Field Data Tests
• Discussion and Future Work
Synthetic Shot Gather
Time (s)
0
Multiples
Primary
4
0
Distance (m)
3000
2D Kirchhoff migration
obs
Source
SA
obs = SA
^
*

RA
+
RA
Receiver
Kirchhoff Migration Image
Depth (km)
0
6
Artificial
Multiple Image
0
Distance (km)
5
Problem
Data
( primary + multiple )
Standard imaging condition
Image
( primary + multiple )
Objective
Data
( primary + multiple )
Primary-Only imaging condition
Image
( primary + multiple )
Outline
• Objective
• POIC Methodology
• Synthetic Data Tests
5-layer model
salt dome model
• Unocal Field Data Tests
• Discussion and Future Work
Methodology
Data
Primary
Multiple
First-order Multiple
=
+
Second-order Multipl
Third-order Multiple
Methodology
Primary ---------------- Multiple
?
What Differences
Primary Reflections
Receiver
^
Source
Depth
*
A
Offset
Multiple Reflections
Receiver
^
Source
*
Depth
B
C
A
Offset
Methodology
For a specific event:
Observed traveltime obs
shooting angle 
incident angle 
Shoot ray from source
Receiver

Depth
*
Offset
^
Source
Shoot ray from receiver
Receiver

Depth
*
Offset
^
Source
Find crossing point
Receiver
Depth
*


SA RA
Cross point A
Offset
^
Source
Primary-Only Imaging
Condition (POIC)
One event is primary reflection
only if :
obs = SA
+
RA
Multiple Reflections
Receiver
Depth
*


SA
RA
A
Offset
^
Source
Multiple Reflections

obs
=

SA
+

RA
Methodology
Data
( primary + multiple )
Primary
Standard
Only
Imaging
Imaging
Condition
obs ,obsand 
Image
( primary + multiple )
Outline
• Objective
• POIC Methodology
• Synthetic Data Tests
5-layer model
salt dome model
• Unocal Field Data Tests
• Discussion and Future Work
5-Layer Model
Source
*
Depth (km)
0
6
Geophone
Line
0
Distance (km)
5
Shot Gather
0
P1
Time (s)
P2
P3
P4
4
0
Distance (m)
3000
Kirchhoff Migration Image
0
Depth (km)
1
2
3
6
4
0
Distance (km)
5
Kirchhoff Migration Image
Depth (km)
0
6
Artificial
Multiple Image
0
Distance (km)
5
Migration Image with POIC
0
Depth (km)
1
2
3
6
4
0
Distance (km)
5
Outline
• Objective
• POIC Methodology
• Synthetic Data Tests
5-layer model
salt dome model
• Unocal Field Data Tests
• Discussion and Future Work
Salt Model
Source
*
Depth (km)
0
3.5
Geophone
Line
0
Distance (km)
5
Shot Gather
Time (s)
0
4
0
Distance (m)
3000
Kirchhoff Migration Image
0
Depth (km)
1
2
3
4
5
6
3.5
0
6
A.M.I.
A.M.I.
A.M.I.
Distance (km)
5
Migration Image with POIC
0
Depth (km)
1
2
3
4
5
6
6
3.5
0
Distance (km)
5
Outline
• Objective
• POIC Methodology
• Synthetic Data Tests
5-layer model
salt dome model
• Unocal Field Data Tests
• Discussion and Future Work
Processed CSG
Time (s)
M1
M2
0
4
175
Distance (m)
3175
NMO Corrected CMG
0
Time (s)
M2
6
175
Distance (m)
3175
CMG after Dip Filtering
0
Time (s)
M2
6
175
Distance (m)
3175
Seismogram in -p Domain
Time (s)
0
6
Multiple
Primary
-200
p
400
Muting in -p Domain
Time (s)
0
6
-200
p
400
CMG after Muting in -p
0
Time (s)
M2
6
175
Distance (m)
3175
Stack before Muting
0
Time (s)
M2
4
M1
M2
313
CDP Number
1400
Stack after Muting
0
Time (s)
M2
4
M2
313
CDP Number
1400
Kirchhoff Image
Depth (m)
0
4000
M2
M1
M2
2000
Distance (m)
9000
POIC Image
0
Depth (ft)
M2
4000
M1
M2
2000
Distance (m)
9000
Conclusions
• POIC Works for synthetic data
• Encouraging results for field data
• POIC need more accurate velocity model
Future Work
• Apply to other field data
• Improve velocity model estimate
Acknowledgement
We are grateful to the 1999 sponsors
of the UTAM consortium for the
financial support
Migration with POIC
Four Steps:
(1) pick seismic events automatically;

obs
Migration with POIC
Four Steps:
(2) calculate incidence and shooting angles
 and  for one event using local slant
stack;
Migration with POIC
Four Steps:
(3) ray tracing and find the crossing point;

SA
+

RA
Find crossing point
Receiver
Depth
*


SA RA
Cross point A
Offset
^
Source
Migration with POIC
(4)
obs = SA
+
RA ?
No: Discard this event;
Yes: Migrate this event;
Raw CSG
Time (s)
0
4
175
Distance (m)
3175
CMG
0
Time (s)
M1
M2
6
175
Offset (m)
3175