WaveEquation Interferometric Migration of VSP Data

1
Wave-Equation Interferometric Migration of VSP
Data

• Ruiqing He
• Dept. of Geology Geophysics
• University of Utah

2
Outline

• Acknowledgements
• Introduction of Seismic Interferometry
• Wave-equation Interferometric Migration
• 3D Migration of VSP Multiples
• Salt Flank Imaging
• Conclusion Technical Contributions

3
Outline

• Acknowledgements
• Introduction of Seismic Interferometry
• Wave-equation Interferometric Migration
• 3D Migration of VSP Multiples
• Salt Flank Imaging
• Conclusion Technical Contributions

4
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.

5
Outline

• Acknowledgements
• Introduction of Seismic Interferometry
• Wave-equation Interferometric Migration
• 3D Migration of VSP Multiples
• Salt Flank Imaging
• Conclusion Technical Contributions

6
Introduction of Seismic Interfeometry

• Passive Seismic Imaging
• Claerbout (1968)
• Katz (1990) Cole (1995)
• Daneshvar et al. (1995)

7
Introduction of Seismic Interfeometry (continued)

• Daylight Imaging
• Rickett Claerbout (1996, 1999, 2000)
• Helioseismologists (Duvall et al., 1993)
• Schuster (1999,2000), Wapenaar (2003)

8
Introduction of Seismic Interfeometry (continued)

• Virtual Source
• Calvert, Bakulin, et al. (2004)

Overburden
Target
9
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

10
Introduction of Seismic Interfeometry (continued)

• Seismic Interferometry Theory

11
Introduction of Seismic Interfeometry (continued)

• Migration of VSP Multiples

12
Introduction of Seismic Interfeometry (continued)

• Successful Applications

Xiao, et al. (2005)
UTAM report
Drilling
13
Introduction of Seismic Interfeometry (continued)

• Robust Imaging

Kirchhoff Migration
KM
Overburden
IM
Interferometric Migration
14
Introduction of Seismic Interfeometry (continued)

• Super Resolution

Kirchhoff Migration
Interferometric Migration
15
Introduction of Seismic Interfeometry (continued)
CDP multiple migration
Various applications
VSP multiple migration
overburden
HSP imaging
Salt Dome
VSP salt flank imaging
16
Outline

• Acknowledgements
• Introduction of Seismic Interferometry
• Wave-equation Interferometric Migration
• 3D Migration of VSP Multiples
• Salt Flank Imaging
• Conclusion Technical Contributions

17
Wave-Equation Interferometric Migration (WEIM)
consideration
IVSP

• Kirchhoff Migration Costs
• Crosscorrelation
• Ray tracing
• Storage for traveltime tables
• For Example
• To obtain 85 x 87 x 1400 migration
• cube, 300 GB disk is required.

18
WEIM theory
IVSP

• WEIM costs for one gather
• One wavefield extrapolation
• One ray tracing
• One traveltime table

19
Ray Tracing
Unknown medium
Known medium
20
3D WEIM of VSP Multiples
21
2D Synthetic Test
Synthetic model
Synthetic data
600 shots
0
0
Time (s)
12 geophpnes
Depth (m)
Multiples
5
4000
0
Offset (m)
0
6000
Offset (m)
6000
22
Migration Comparison
Migration of primaries
Migration of multiples
0
0
Depth (m)
Depth (m)
4000
4000
0
Offset (m)
0
6000
Offset (m)
6000
23
Field Data Application
24
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
25
3D WEIM Result
Migration of only one receiver gather
26
Slice Movie
Migration of only one receiver gather
27
Slice of 3D Migration Cube
0
Depth (m)
6500
Offset (m)
11000
0
28
Common Image Gather
0
Depth (m)
6500
Offset (m)
1
36
29
VSP Salt Flank Imaging
Overburden
30
Interferometric Migration Result
31
A Synthetic Experiment
10 shots
Overburden
94 geophones
32
A Shot Gather
33
WEIM Result (one shot)
2700
Depth (m)
Artifacts
5500
0
1700
Offset (m)
34
WEIM Result (ten shots)
2700
Depth (m)
5500
0
1700
Offset (m)
35
Outline

• Acknowledgements
• Introduction of Seismic Interferometry
• Wave-equation Interferometric Migration
• 3D Migration of VSP Multiples
• Salt Flank Imaging
• Conclusion Technical Contributions

36
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.

37
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.

38
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.

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The End

• Thank you.