Wave-Equation Interferometric Migration of VSP Data Ruiqing He Dept. of Geology & Geophysics University of Utah

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

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

Acknowledgements Thank Jerry Schuster for enlightening lectures, innovating discussions, supervising and support. 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 Bob Smith, Cari Johnson, Kris Sikorski for teaching and supervising. Thank Yue Wang for supervising. Thank my family. Thank my family.

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

Introduction of Seismic Interfeometry Passive Seismic Imaging: Passive Seismic Imaging: –Claerbout (1968) –Katz (1990); Cole (1995) –Daneshvar et al. (1995)

Introduction of Seismic Interfeometry (continued) Daylight Imaging: Daylight Imaging: –Rickett & Claerbout (1996, 1999, 2000) –Helioseismologists (Duvall et al., 1993) –Schuster (1999,2000), Wapenaar (2003)

Introduction of Seismic Interfeometry (continued) Virtual Source: Virtual Source: –Calvert, Bakulin, et al. (2004) Overburden Target

Introduction of Seismic Interfeometry (continued) Seismic Interferometry: 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: Seismic Interferometry Theory:

Introduction of Seismic Interfeometry (continued) Migration of VSP Multiples: Migration of VSP Multiples:

Introduction of Seismic Interfeometry (continued) Successful Applications: Successful Applications: Xiao, et al. (2005) UTAM report Drilling … 3D

Introduction of Seismic Interfeometry (continued) Robust Imaging: Robust Imaging: Kirchhoff Migration Interferometric Migration KM IM Overburden

Introduction of Seismic Interfeometry (continued) Super Resolution: Super Resolution: Kirchhoff MigrationInterferometric Migration

VSP salt flank imaging HSP imaging VSP multiple migration CDP multiple migration Salt Dome Introduction of Seismic Interfeometry (continued) Various applications: overburden

Outline Acknowledgements Acknowledgements Introduction of Seismic Interferometry Introduction of Seismic Interferometry Wave-equation Interferometric Migration Wave-equation Interferometric Migration –3D Migration of VSP Multiples –Salt Flank Imaging Conclusion & Technical Contributions 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 WEIM costs for one gather: 1)One wavefield extrapolation 2)One ray tracing 3)One traveltime table IVSP

Ray Tracing Known medium Unknown 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 Offset (m) Depth (m) Offset (m) Time (s) 0 5 Synthetic modelSynthetic data 12 geophpnes 600 shots Multiples

Migration Comparison Offset (m) Depth (m) Migration of primariesMigration of multiples Offset (m) Depth (m)

Field Data Application

Survey Geometry Each geophone group has 12 geophones. ~ 11 km ~ 5 km deep 3 similar spirals, each corresponding to an offset-ed geophone group.

3D WEIM Result Migration of only one receiver gather

Slice Movie Migration of only one receiver gather

Slice of 3D Migration Cube Offset (m) Depth (m)

Common Image Gather Offset (m)136 Depth (m)

VSP Salt Flank Imaging ? 98 geophones 120 shots Overburden

Interferometric Migration Result

A Synthetic Experiment 94 geophones 10 shots Overburden

A Shot Gather

WEIM Result (one shot) Offset (m) Depth (m) Artifacts

WEIM Result (ten shots) Offset (m) Depth (m)

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

Conclusion Seismic interferometry is a robust imaging tool, and has a variety of applications. 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. 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. 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: 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.