Transcript Prestack Elastic Reverse Time Migration

Imaging Multiple
Reflections with ReverseTime Migration
Yue Wang
University of Utah
Outline
•
•
•
•
•
Background
Motivation & Objective
Methodology
Numerical Examples
Conclusions
Forward Process
Source
Geophone Line
*
Depth (km)
0
1
0
Distance (km)
4.5
Forward Process
*
Depth (km)
0
obs
1
0
Distance (km)
4.5
Reverse Time Migration
Reversed traces
0
Depth (km)
obs
Extrapolated Wavefield
1
0
Distance (km)
4.5
obs
Reverse-Time Migration
Extrapolated Wavefield
Imaging Condition
Migration Section
Outline
•
•
•
•
•
Background
Motivation & Objective
Methodology
Numerical Examples
Conclusions
Ocean-Bottom Survey
Source
Geophone Line
*
Depth (km)
0
1
0
Distance (km)
4.5
Problem
Receiver-side Multiples
*
Depth (km)
0
1
0
Distance (km)
4.5
Synthetic Shot Gather
Time (s)
0
Receiver side multiples
2
0.9
Distance (km)
3.6
Field Data
Time (s)
0
Receiver side multiples
4
-80
Distance (m)
1900
Time Migration
Time (s)
0
Receiver side multiples
4
-80
Distance (m)
1900
Objective
• Using both primary and multiple
reflections for imaging by reversetime migration.
Outline
•
•
•
•
•
Background
Motivation & Objective
Methodology
Numerical Examples
Conclusions
Ocean-Bottom Survey
Source
Geophone Line
*
Depth (km)
0
1
0
Distance (km)
4.5
Ocean-Bottom Survey
P
*
V
Depth (km)
0
Up-going
1
0
Distance (km)
Multi-Component Data
ocean-bottom survey
pressure + particle velocity
( P & V )
Reverse Time Migration
( P & V Scheme )
P
V
1
Down-going
Depth (km)
0
0
Distance (km)
Reverse Time Migration
( Particle Velocity Only )
V
Depth (km)
0
1
0
Distance (km)
Key Idea
Primary + Multiple
P & V Scheme
Correct Positions
Key Idea
Primary + Multiple
V-Only Scheme
Incorrect Positions
Ocean-Bottom Survey
P
*
V
Depth (km)
0
Up-going Waves
1
0
Distance (km)
P & V Scheme
P
V
Depth (km)
0
Correct Position
Down-going waves
1
0
Distance (km)
Particle Velocity Only Scheme
V
Depth (km)
0
Incorrect
1
0
Distance (km)
Ocean-Bottom Survey
P
*
V
Depth (km)
0
Down-going waves
( Multiples )
1
0
Distance (km)
P & V Scheme
P
V
Depth (km)
0
Correct Position
1
0
Distance (km)
Up-going waves
Particle Velocity Only Scheme
V
Depth (km)
0
Incorrect
1
0
Distance (km)
Outline
•
•
•
•
Background
Motivation & Objective
Methodology
Numerical Examples
Salt Dome Model
• Conclusions
Salt Model
Depth (km)
0
2.7
0
Distance (km)
4.5
Shot Gather
Vertical
Normal Stress
Time (s)
0
Horizontal
Multiples
2
0.9 Distance (km) 3.6 0.9 Distance (km) 3.6 0.9 Distance (km) 3.6
Kirchhoff Migration
Depth (km)
0
2.5
0.45
Distance (km)
4.05
Kirchhoff Migration
Depth (km)
0
2.5
0.45
Distance (km)
4.05
Particle Velocity Only Scheme
Depth (km)
0
2.7
0.45
Distance (km)
4.05
Particle Velocity Only Scheme
Depth (km)
0
2.7
0.45
Distance (km)
4.05
P & V Scheme
Depth (km)
0
2.5
0.45
Distance (km)
4.05
P & V Scheme
Depth (km)
0
2.5
0.45
Distance (km)
4.05
Conclusion
Primary + Multiple
P + V RTM
Correct Positions
Future Work: Field Data Test
Time (s)
0
Receiver side multiples
4
-80
Distance (m)
1900
Acknowledgement
We are grateful to the 1999 sponsors
of the UTAM consortium for the
financial support
Outline
•
•
•
•
Background
Motivation & Objective
Methodology
Numerical Examples
Plane-wave example
• Conclusions
Depth
Forward Process
Up-going waves
Distance
Depth
P & V Scheme
Down-going waves
Distance
P & V Scheme
Depth (km)
0
Down-going waves
1.2
0
Time (s)
0.8
Particle Velocity Only Scheme
Depth
Up-going waves
Down-going waves
Distance
Particle Velocity Only Scheme
0
Depth (km)
Up-going waves
Down-going waves
1.2
0
Time (s)
0.8
P + V RTM
Depth (km)
Depth (km)
0 0
Up-going waves
PP
Correct Position
1 1
Distance
(km)
0 0 Distance
(km)
+
V
Down-going
waves
Up-going
waves