Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang...
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![Page 1: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/1.jpg)
Time-reversal acoustics, virtual source imaging, and seismic interferometry
Haijiang Zhang
University of Science and Technology of China
![Page 2: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/2.jpg)
Time-reversal acoustics
Fink, 1997
![Page 3: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/3.jpg)
![Page 4: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/4.jpg)
Time-reversal and super resolution
More heterogeneous and scattered the medium between the source and the TRM, the more focused the time-reversed signal.
![Page 5: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/5.jpg)
Time-reversed seismic location
– No picking required
– Automatic (real-time) location
– Using full waveforms
![Page 6: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/6.jpg)
Virtual source method
Bakulin and Calvert, 2006
Sources Sk on the surface
Receivers in the borehole
The goal is to construct seismic record from virtual source to receivers.
![Page 7: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/7.jpg)
Synthetic velocity models
![Page 8: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/8.jpg)
Virtual source gather (at 900 m) Real source gather (at 900 m)
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Constructing virtual source (VS) data
€
Ska (t) = wk (t) ˜ S ka (t)
Bakulin and Calvert, 2006
![Page 10: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/10.jpg)
Problem: Overburden+statics defocus VSP migration
Redatum sources below overburdenLocal VSP migration
Solution: VSP -> SWP Transform (Calvert, Bakulin)
Applications
VSPVSP SWP
Shuster, SEG 09
![Page 11: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/11.jpg)
VSP Geometry
Offset (m)0 1000
Depth (m)
1500
3500Time (s)
0
3
Reflection wavefield
(He , 2006)
![Page 12: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/12.jpg)
VSP Geometry
Offset (m)0 1000
Depth (m)
1500
3500
(He , 2006)
Time (s)
0
3
Reflection wavefield
superresolution
China
![Page 13: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/13.jpg)
VSP Salt Flank Imaging (Hornby & Yu, 2006)
? 98 geophones
120 shots
Overburden
Poor image of flank by standard migration
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Interferometric Migration Result
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Seismic Interferometry
• Interferometry is a family of techniques in which waves, are superimposed in order to extract information about the waves (from wikipedia).
• Seismic Interferometry involves cross correlating and stacking diffusive waves to extract Green’s functions.
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Cross-correlation and stacking
Gsa(t): Green’s function from source s to a.e(t): Source time function.
Cross-correlation
Stacking: source averaging
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Homogeneous medium
Circular sources
a) τ= -3T0
b) τ= -T0
c) Τ=10T0
Larose et al., 2005
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Homogeneous medium
800 sources (partially covered)
a) τ= -3T0
b) τ= -T0
c) Τ=10T0
![Page 20: Time-reversal acoustics, virtual source imaging, and seismic interferometry Haijiang Zhang University of Science and Technology of China.](https://reader035.fdocuments.us/reader035/viewer/2022070306/551771405503460e6e8b4f6c/html5/thumbnails/20.jpg)
Heterogeous medium
800 sources (partially covered)
a) first-part coda b) late coda
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Time-reversal interpretation of the correlation process
Treat a as the virtual source
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(Weaver and Lobkis, Ultrasonics, 40, 435-439, 2002)
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20 30 40 50 60 70 80 90 100 110
-4500
-4000
-3500
-3000
-2500
-2000
-1500
-1000
-500
0
500
1000
1500
2000
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
time (microseconds)
Pulse/echo
noiseautocorrelation
(Weaver and Lobkis, Ultrasonics, 40, 435-439, 2002)
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