virtual source imaging and seismic interferometry Haijiang Zhang University of Science and Technology of China Timereversal acoustics Fink 1997 Timereversal and super resolution More heterogeneous and scattered the medium between the source and the TRM the more focused the timerever ID: 320615
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Slide1
Time-reversal acoustics, virtual source imaging, and seismic interferometry
Haijiang Zhang
University of Science and Technology of ChinaSlide2
Time-reversal acoustics
Fink, 1997Slide3Slide4
Time-reversal and super resolution
More heterogeneous and scattered the medium between the source and the TRM, the more focused the time-reversed signal. Slide5
Time-reversed seismic location
No picking required
Automatic (real-time) location
Using full waveformsSlide6
Virtual source method
Bakulin
and Calvert, 2006
Sources
S
k
on the surface
Receivers in the borehole
The goal is to construct seismic record from virtual source to receivers. Slide7
Synthetic velocity modelsSlide8
Virtual source gather (at 900
m
)
Real source gather (at 900
m
)Slide9
Constructing virtual source (VS) data
Bakulin
and Calvert, 2006Slide10
Problem:
Overburden+statics defocus VSP migration
Redatum sources below overburden
Local VSP migration
Solution:
VSP -> SWP Transform (Calvert, Bakulin)
Applications
VSP
VSP
SWP
Shuster, SEG 09Slide11
VSP Geometry
Offset (m)
0
1000
Depth
(m)
1500
3500
Time
(s)
0
3
Reflection
wavefield
(He , 2006)Slide12
VSP Geometry
Offset (m)
0
1000
Depth
(m)
1500
3500
(He , 2006)
Time
(s)
0
3
Reflection
wavefield
superresolution
ChinaSlide13
VSP Salt Flank Imaging
(Hornby & Yu, 2006)
?
98 geophones
120 shots
Overburden
Poor
image of flank by standard migrationSlide14
Interferometric Migration ResultSlide15Slide16
Seismic InterferometryInterferometry
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.Slide17
Cross-correlation and stacking
G
sa
(t
): Green’s function from source
s
to
a
.
e
(t
): Source time function.
Cross-correlation
Stacking: source averagingSlide18
Homogeneous medium
Circular sources
τ
= -3T
0
τ
= -T
0
Τ
=10T
0
Larose et al., 2005Slide19
Homogeneous medium
800 sources (partially covered)
τ
= -3T
0
τ
= -T
0
Τ
=10T
0Slide20
Heterogeous
medium
800 sources (partially covered)
a) first-part coda
b
) late codaSlide21
Time-reversal interpretation of the correlation process
Treat
a
as the virtual source Slide22
(Weaver and Lobkis, Ultrasonics,
40
, 435-439, 2002)Slide23
(Weaver and Lobkis, Ultrasonics,
40
, 435-439, 2002)Slide24Slide25Slide26