Migration and Attenuation of SurfaceRelated and Interbed Multiple Reflections

1
Migration and Attenuation of Surface-Related and
Interbed Multiple Reflections
Zhiyong Jiang
University of Utah
April 21, 2006
2
Outline

• Overview
• Surface Multiple Migration
• Interbed Multiple Migration
• Multiple Attenuation in
• Multiple Imaging
• Conclusions

3
Primary
s
g
x
4
Technical Contributions

• For the first time, I examine the imaging and
  computational properties of three different
  surface multiple imaging methods, and apply them
  to both synthetic and field data

• I develop two novel methods for imaging
  interbed multiples, and apply them to field and
  synthetic data

• I attenuate high-order multiples to solve a
  major problem in multiple imaging the
  interference from other multiples. This strategy
  makes multiple imaging a more practical tool

5
Outline

• Overview
• Surface Multiple Migration
• Interbed Multiple Migration
• Multiple Attenuation in
• Multiple Imaging
• Conclusions

6
Outline

• Overview
• Surface Multiple Migration
• Motivation
• Methodology
• Numerical Results
• Summary

7
Why Migrate Surface Multiples?
Better Vert. Res.
8
3D VSP Survey
Shot radius
Z
9
Outline

• Overview
• Surface Multiple Migration
• Motivation
• Methodology
• Numerical Results
• Summary

10
Modeling Equation
s
B0
g
11
Method 1 Model-based Multiple Imaging
m(x, ?) ?? d(s, g)mult.
.
exp-i? (tsx txg tgg) dsdg
0
0
txg tgg min (txg tgg)
0
0
g
B0
B0
g0
s
tgg
g diffraction point g0 specular pointX
trial image point
0
tsx
txg
0
g
x
12
Method 2 Mig. with Semi-natural Greens functions
m(x, ?) ?? d(s, g)mult.

.
exp-i? (tsx txg tgg) dsdg
0
0


txg tgg min (txg tgg)
0
0
g
B0
B0
g0
s

tgg
g diffraction point g0 specular pointX
trial image point
0
tsx
txg
0
g
x
13
Method 3 Interferometric Imaging
m(x, ?) ??? d(s, g)mult.

.
exp-i? (tsx txg tgg) dsdgdg
g
s
B0
g diffraction point X trial image point
tsx
g
x
14
Imaging Properties of Migration Methods
15
Outline

• Overview
• Surface Multiple Migration
• Motivation
• Methodology
• Numerical Results
• Summary

16
Numerical Results

• 2-D Dipping Layer Model
• 3-D Real Data
• 3-D Synthetic Data

17
Velocity Model
Well
X (m)
925
0
0
V (m/s)
4000
Depth (m)
1900
1300
Shots 92 Receivers 91 (50m -950 m)
18
CSG 51
Ghost Component
0
S
A
Time (s)
Well
G
X
3
50
950m
50
950m
19
CSG 51
Primary Component
0
Time (s)
S
A
Well
G
X
3
50
950m
50
950m
20
8 Receivers
Primary
1st-order multiple
0
Depth (m)
1300
X (m)
0
0
X (m)
925
925
21
Numerical Results

• 2-D Dipping Layer Model
• 3-D Real Data
• 3-D Synthetic Data

22
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23
Numerical Results

• 2-D Dipping Layer Model
• 3-D Real Data
• 3-D Synthetic Data

24
Sources/Wells Locations
Y (m)
0
2000
0
Well
X (m)
1089 shots 111 receivers
2000
25
CSG10
CSG540
0
Time (s)
X
3.5
1
111
1
Receiver Number
Receiver Number
111
26
X1000m
Primary
100
Depth (m)
1100
Velocity Model
100
Depth (m)
1100
Y (m)
0
2000
27
X1000m
1st order ghost
100
Depth (m)
1100
Velocity Model
100
Depth (m)
1100
Y (m)
0
2000
28
Y1000m
Primary
100
Depth (m)
1100
Velocity Model
100
Depth (m)
1100
X (m)
0
2000
29
Y1000m
1st order ghost
100
Depth (m)
1100
Velocity Model
100
Depth (m)
1100
X (m)
0
2000
30
Outline

• Overview
• Surface Multiple Migration
• Motivation
• Methodology
• Numerical Results
• Summary

31
Summary
Advantages
Wider subsurface coverage can be achieved by
migrating multiples
Multiples illuminate areas invisible to primaries
32
Summary
Limitation
Multiple is weak
Interferences from primary and other events,
such as high-order multiples
33
Outline

• Overview
• Surface Multiple Migration
• Interbed Multiple Migration
• Multiple Attenuation in
• Multiple Imaging
• Conclusions

34
Outline

• Overview
• Interbed Multiple Migration
• Motivation
• Methods
• Numerical Tests
• Summary

35
What is below the salt?
?
36
Challenge with VSP Surface Multiples Long
raypath, strong attenuation, triple passage
through salt
s
g
37
Challenge with CDP primary reflectionsstrong
attenuation, double passage through salt
g
s
38
Can we try interbed multiples?Advantages short
raypth, less attenuation, single passage through
salt
s
g
39
Outline

• Overview
• Interbed Multiple Migration
• Motivation
• Methods
• Numerical Tests
• Summary

40
Modeling Equation
B0
s
B1
g
41
Method 1 Fermats principle
m(x, ?) ?? d(s, g)inter.
.
exp-i? (tsx txg tgg) dsdg
0
0
txg tgg min (txg tgg)
0
0
g
B1
B0
s
g0
B1
tgg
tsx
0
txg
0
g
x
42
Method 2 Summation of all the diffraction energy
m(x, ?) ??? d(s, g)inter.
.
exp-i? (tsx txg tgg) dsdgdg
B0
s
g
B1
tsx
x
g
43
Outline

• Overview
• Interbed Multiple Migration
• Motivation
• Methods
• Numerical Tests
• Summary

44
Numerical Tests

• SEG/EAGE Model
• Large Salt Model
• Field Data Test

45
Velocity Model
X (m)
3000
0
Depth (m)
2000
Shots 301 Receivers 61 (1000m - 1600m)
46
Upper-salt-boundary Interbed Multiple
0
s
g0
Depth (m)
g
x
2000
3000
0
X (m)
47
Velocity Model
Interbed Multiple Migration Image
800
Depth (m)
2000
1200
1200
0
0
X (m)
X (m)
48
Lower-salt-boundary Interbed Multiple
0
s
Depth (m)
g0
g
x
2000
3000
0
X (m)
49
Interbed Multiple Migration Image
Velocity Model
800
Depth (m)
2000
1200
1200
0
0
X (m)
X (m)
50
Numerical Tests

• SEG/EAGE Model
• Large Salt Model
• Field Data Test

51
Velocity Model
X (m)
16000
0
0
Depth (m)
11000
Shots 319 Receivers 21
52
Lower-salt-boundary Interbed Multiple
0
s
Depth (m)
g0
x
g
11000
16000
0
X (m)
53
Velocity Model
6250
Depth (m)
7250
1200
0
X (m)
Interbed Multiple Migration Image
6250
Depth (m)
7250
1200
0
X (m)
54
Numerical Tests

• SEG/EAGE Model
• Large Salt Model
• Field Data Test

55
Velocity Model
16000m
0
0
Depth (m)
10668
Shots 102 Receivers 12
56
Sea-bed Interbed Multiple
16000m
0
0
s
g0
x
Depth (m)
g
10668
57
Velocity Model
2000
Depth (m)
4000
Interbed Multiple Migration Image
2000
Depth (m)
4000
0
4000
X (m)
58
Outline

• Overview
• Interbed Multiple Migration
• Motivation
• Methods
• Numerical Tests
• Summary

59
Summary

• Interbed multiples are used to image salt
• boundaries and subsalt structures

• Challenge Accuracy of the multiple
• generating interface

• Challenge Interference from other multiples

60
Outline

• Overview
• Surface Multiple Migration
• Interbed Multiple Migration
• Multiple Attenuation in
• Multiple Imaging
• Conclusions

61
Outline

• Overview
• Multiple Attenuation in
• Multiple Imaging
• Motivation
• Methodology
• Numerical Examples
• Summary

62
A major problem with multiple imaging
high-order multiple
Incorrectly positioned as low-order multiple
63
Outline

• Overview
• Multiple Attenuation in
• Multiple Imaging
• Motivation
• Methodology
• Numerical Examples
• Summary

64
Step1 Prediction
second-order multiple
65
Physics Behind Prediction
D(g s) ? G(g g) D(g s) dg
D(gs) Downgoing component
G(gg) Greens function for
propagating the wavefield
D(gs) Predicted high-order multiples
66
Step2 Subtraction
p(t) y(t) - ? fj(t)?mj(t)
Predicted high-order multiple
Original data
High-order multiple-free data
67
Outline

• Overview
• Multiple Attenuation in
• Multiple Imaging
• Motivation
• Methodology
• Numerical Examples
• Summary

68
Numerical Examples

• Synthetic Data Test
• Field Data Test

69
Density Model
276 shots, 50m spacing
0
20 receivers 6.25m spacing
Depth (m)
6,000
14,000
0
X (m)
70
CRG1 Different Order Multiples
71
Before Attenuation
0.4
Time (sec)
2.5
0
14,000
X (m)
72
Prediction
0.4
Time (sec)
2.5
0
14,000
X (m)
73
After Attenuation
0.4
Time (sec)
2.5
0
14,000
X (m)
74
Before Attenuation
0.4
Time (sec)
2.5
0
14,000
X (m)
75
Migration Image Before Attenuation
500
Interference from high-order multiple
Depth (m)
6000
12500
1500
X (m)
76
Migration Image After Attenuation
500
Depth (m)
6000
12500
1500
X (m)
77
Numerical Examples

• Synthetic Data Test
• Field Data Test

78
Velocity Model
0
V (ft/s)
4910
Depth (ft)
14300
43000
0
60000
X (ft)
79
Different Order Multiples
80
Before Attenuation
1.25
1st-order multiple
Time (sec)
2nd-order multiple
5.00
0
60000
X (ft)
81
Predicted Multiple
1.25
Time (sec)
5.00
0
60000
X (ft)
82
After Attenuation
1.25
Time (sec)
5.00
0
60000
X (ft)
83
Before Attenuation
1.25
1st-order multiple
Time (sec)
2nd-order multiple
5.00
0
60000
X (ft)
84
Multiple Migration Image Before Attenuation
10
interference from high-order multiple
Depth (kft)
26
16
X (kft)
32
85
Multiple Migration Image After Attenuation
10
Depth (kft)
26
16
X (kft)
32
86
Multiple Migration Images Comparison
10
Depth (kft)
26
X (kft)
16
32
87
Outline

• Overview
• Multiple Attenuation in
• Multiple Imaging
• Motivation
• Methodology
• Numerical Examples
• Summary

88
Summary

• Attenuate high-order multiples to better image
• low-order multiples, making multiple imaging a
• more practical and useful tool

• Obtained cleaner and more accurate subsurface
• images to help avoid misinterpretation and
  thus
• reduce risk in subsequent processes

89
Outline

• Overview
• Surface Multiple Migration
• Interbed Multiple Migration
• Multiple Attenuation in
• Multiple Imaging
• Conclusions

90
Conclusions

• As shown in the numerical examples,
• surface multiple imaging and interbed
• multiple imaging can be important imaging
• methods

• The multiple attenuation process is effective
• in mitigating the interference in multiple
• imaging

91
Future Work

• Apply interbed multiple imaging to more field
• data sets

• Apply data-based multiple prediction method
• in multiple filtering

• Attenuate surface multiples prior to imaging
• interbed multiples

92
Acknowledgements

• My advisor Gerard T. Schuster

• My supervisory committee Ronanld L. Bruhn,
• Brian E. Hornby, Richard D. Jarrard, and
  Robert
• B. Smith

• My wife Weining and my daughter Julia

• My UTAM colleagues and my other friends

93
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