Jianhua Yu University of Utah Robust Imaging for RVSP Data with Static Errors

Outline Problems in RVSP imaging How to eliminate the static errors in RVSP imaging Synthetic and real data examples Summary

Outline Problems in RVSP imaging How to eliminate the static errors in RVSP imaging Synthetic and real data examples Summary

Well Geophone ? RVSP Acquistion Geometry

Problems in RVSP imaging Don’t know initial time Have limitation to deviated well Don’t know source wavelet Static shift error may exist

Do not require source waveletDo not require source wavelet Image conditions:Image conditions: ( a) Primary reflection (solid line) (b) ghost reflection (solid line) Autocorrelogram Migration

Migration Formula: Migrated Image Autocorrelograms of seismic data

Outline Problems in RVSP imaging How to eliminate the static errors in RVSP imaging Synthetic and real data examples Summary

Primary Auto. Migration:

Outline Problems in RVSP imaging How to eliminate the static errors in RVSP imaging Synthetic and real data examples Summary

Depth (ft) RVSP and Geology Model 98 sources 25 geophones 625 ft Well

Time (s) CRG 16 Depth (kft) CRG 2

Time (s) CRG 2 Depth (kft) CRG 16

Time (s) Autocorr. CRG 2 Depth (kft) Autocorr. CRG 16

Depth (ft) No static errors With static errors Primary Kichhoff Migration

Depth (ft) No static errors With static errors Primary Autocorr. Migration

Depth (ft) Kirchhoff Autocorr. Mig

Depth (ft) No static errors With static errors Ghost Kirchhoff Migration

Depth (ft) No static errors With static errors Ghost Autocorr. Migration

Depth (ft) Kirchhoff Autocorr Mig (Ghost)

Outline Problems in RVSP imaging How to eliminate the static errors in RVSP imaging Synthetic and real data examples Summary

Time (s) CRG 6CRG 15 Depth (kft)

Time (s) CRG 6: primaryCRG 15: primary Depth (kft)

Time (s) Autocorr. CRG 6: primaryAutocorr. CRG 15: primary Depth (kft)

Time (s) Autocorr. CRG 6: ghostAutocorr. CRG 15: ghost Depth (kft)

Depth (ft) Kirchhoff Mig. with Primary 120 ft

Depth (ft) Well Log and Kirchhoff Migration

Depth (ft) Autocorr. Mig. with Primary 120 ft

Depth (ft) Well Log and Primary Autocorr. Mig

Depth (ft) Kirchhoff Mig. Primary Auto. Mig. WellWellMigMig  Primary autocorrelogram migration gives better correlation with well log synthetic seismograms

Depth (ft) Auto mig. with P+G 120 ft

Depth (ft) Well Log and Mig without Separating Primary and Ghost

Depth (ft) Joint mig. with P+G 120 ft

Depth (ft) Well log and Joint Mig. with Primary and Ghost

Depth (ft) Mig. With P+G WellMig Joint Mig. With P+G WellMig

Outline Problems in RVSP imaging How to eliminate the static errors in RVSP imaging Synthetic and real data examples Summary

Summary Autocorrelogram imaging condition is capable of suppressing static shift errorsAutocorrelogram imaging condition is capable of suppressing static shift errors It can be used to image reflectivity with static error-polluted VSP and drill-bit data where no pilot signal is availableIt can be used to image reflectivity with static error-polluted VSP and drill-bit data where no pilot signal is available

Acknowledgments Thank 2002 sponsors of UTAM consortium for the financial supportThank 2002 sponsors of UTAM consortium for the financial support Thank Exxon for providing the real dataThank Exxon for providing the real data