Transcript Virtual Source and Natural Imaging Techniques

Wave-Equation
Interferometric Migration
of VSP Data
Ruiqing He
Dept. of Geology & Geophysics
University of Utah
Outline
• Acknowledgements
• Introduction of Seismic Interferometry
• Wave-equation Interferometric Migration
– 3D Migration of VSP Multiples
– Salt Flank Imaging
• Conclusion & Technical Contributions
Outline
• Acknowledgements
• Introduction of Seismic Interferometry
• Wave-equation Interferometric Migration
– 3D Migration of VSP Multiples
– Salt Flank Imaging
• Conclusion & Technical Contributions
Acknowledgements
• Thank Jerry Schuster for enlightening
lectures, innovating discussions,
supervising and support.
• Thank Bob Smith, Cari Johnson, Kris
Sikorski for teaching and supervising.
Thank Yue Wang for supervising.
• Thank my family.
Outline
• Acknowledgements
• Introduction of Seismic Interferometry
• Wave-equation Interferometric Migration
– 3D Migration of VSP Multiples
– Salt Flank Imaging
• Conclusion & Technical Contributions
Introduction of
Seismic Interfeometry
• Passive Seismic Imaging:
– Claerbout (1968)
– Katz (1990); Cole (1995)
– Daneshvar et al. (1995)
Introduction of
Seismic Interfeometry
(continued)
• Daylight Imaging:
– Rickett & Claerbout (1996, 1999, 2000)
– Helioseismologists (Duvall et al., 1993)
– Schuster (1999,2000), Wapenaar (2003)
Introduction of
Seismic Interfeometry
(continued)
• Virtual Source:
– Calvert, Bakulin, et al. (2004)
Overburden
Target
Introduction of
Seismic Interfeometry
(continued)
• Seismic Interferometry:
– Schuster & Rickett (1999)
– Schuster (2001)
– Yu & Schuster (2001, 2006)
– Jiang et al. (2005)
• No restriction on source distribution
• Arbitrary velocity model
• Many types of events used
Introduction of
Seismic Interfeometry
(continued)
• Seismic Interferometry Theory:
Introduction of
Seismic Interfeometry
• Migration of VSP Multiples:
(continued)
Introduction of
Seismic Interfeometry
(continued)
• Successful Applications:
3D
Xiao, et al. (2005)
UTAM report
Drilling …
Introduction of
Seismic Interfeometry
(continued)
• Robust Imaging:
Kirchhoff Migration
KM
Overburden
IM
Interferometric Migration
Introduction of
Seismic Interfeometry
(continued)
• Super Resolution:
Kirchhoff Migration
Interferometric Migration
Introduction of
Seismic Interfeometry
Various applications:
(continued)
CDP multiple migration
VSP multiple migration
overburden
HSP imaging
Salt Dome
VSP salt flank imaging
Outline
• Acknowledgements
• Introduction of Seismic Interferometry
• Wave-equation Interferometric Migration
– 3D Migration of VSP Multiples
– Salt Flank Imaging
• Conclusion & Technical Contributions
Wave-Equation Interferometric
Migration (WEIM): consideration
Kirchhoff Migration Costs:
1) Crosscorrelation
2) Ray tracing
3) Storage for traveltime tables
For Example:
To obtain 85 x 87 x 1400 migration
cube, ~300 GB disk is required.
IVSP
WEIM:
theory
IVSP
WEIM costs for one gather:
1) One wavefield extrapolation
2) One ray tracing
3) One traveltime table
Ray Tracing
Unknown
medium
Known
medium
The picked time is imposed as an initial condition in ray tracing.
It is as efficient as conventional point-source ray tracing.
3D WEIM of VSP Multiples
2D Synthetic Test
Synthetic model
Synthetic data
600 shots
Depth (m)
12 geophpnes
Time (s)
0
0
Multiples
5
4000
0
Offset (m)
6000
0
Offset (m)
6000
Migration Comparison
Migration of primaries
Migration of multiples
0
Depth (m)
Depth (m)
0
4000
4000
0
Offset (m)
6000
0
Offset (m)
6000
Field Data Application
Survey Geometry
~ 11 km
~ 11 km
3 similar spirals,
each corresponding
to an offset-ed
geophone group.
Each geophone group
has 12 geophones.
~ 5 km deep
3D WEIM Result
Migration of only one receiver gather
Slice Movie
Migration of only one receiver gather
Slice of 3D Migration Cube
Depth (m)
0
6500
0
Offset (m)
11000
Common Image Gather
Depth (m)
0
6500
1
Offset (m)
36
VSP Salt Flank Imaging
120 shots
Overburden
?
98 geophones
Interferometric Migration Result
A Synthetic Experiment
10 shots
Overburden
94 geophones
A Shot Gather
WEIM Result (one shot)
Depth (m)
2700
Artifacts
5500
0
Offset (m)
1700
WEIM Result (ten shots)
Depth (m)
2700
5500
0
Offset (m)
1700
Outline
• Acknowledgements
• Introduction of Seismic Interferometry
• Wave-equation Interferometric Migration
– 3D Migration of VSP Multiples
– Salt Flank Imaging
• Conclusion & Technical Contributions
Conclusion
• Seismic interferometry is a robust imaging
tool, and has a variety of applications.
• However, the relatively weak energy
waves and low fold imaging in some
applications could result in the low S/N
ratio of the image.
Technical Contributions (I)
• Wave-equation interferometric migration is
proposed for efficient 3D migration of VSP
multiples.
– It is as robust to velocity estimation errors as surface
seismic imaging.
– It is much more cost efficient than surface seismic
surveys in obtaining a 3D subsurface image volume.
– It might be also useful for time-lapse (4D) seismic
monitoring for some oil fields.
Technical Contributions (II)
• Apply interferometric migration to salt
flank imaging with VSP data:
– A huge chunk of overburden is ignored, so
that the imaging is not only efficient, but also
robust to velocity estimation errors.
– Other vertical structures, such as faults that
are difficult to image by surface seismic
surveys could also be imaged.
The End
Thank you.