Wave-Equation Wave-Equation Interferometric Migration Interferometric Migration

of VSP Dataof VSP Data

Ruiqing HeRuiqing He

Dept. of Geology & Dept. of Geology & GeophysicsGeophysics

University of UtahUniversity of Utah

OutlineOutline

• AcknowledgementsAcknowledgements

• Introduction of Seismic InterferometryIntroduction of Seismic Interferometry

• Wave-equation Interferometric MigrationWave-equation Interferometric Migration– 3D Migration of VSP Multiples3D Migration of VSP Multiples– Salt Flank ImagingSalt Flank Imaging

• Conclusion & Technical ContributionsConclusion & Technical Contributions

OutlineOutline

• AcknowledgementsAcknowledgements

• Introduction of Seismic InterferometryIntroduction of Seismic Interferometry

• Wave-equation Interferometric MigrationWave-equation Interferometric Migration– 3D Migration of VSP Multiples3D Migration of VSP Multiples– Salt Flank ImagingSalt Flank Imaging

• Conclusion & Technical ContributionsConclusion & Technical Contributions

AcknowledgementsAcknowledgements

• Thank Jerry Schuster for enlightening Thank Jerry Schuster for enlightening lectures, innovating discussions, lectures, innovating discussions, supervising and support.supervising and support.

• Thank Bob Smith, Cari Johnson, Kris Thank Bob Smith, Cari Johnson, Kris Sikorski for teaching and Sikorski for teaching and supervising. Thank Yue Wang for supervising. Thank Yue Wang for supervising.supervising.

• Thank my family.Thank my family.

OutlineOutline

• AcknowledgementsAcknowledgements

• Introduction of Seismic InterferometryIntroduction of Seismic Interferometry

• Wave-equation Interferometric MigrationWave-equation Interferometric Migration– 3D Migration of VSP Multiples3D Migration of VSP Multiples– Salt Flank ImagingSalt Flank Imaging

• Conclusion & Technical ContributionsConclusion & Technical Contributions

Introduction of Introduction of Seismic InterfeometrySeismic Interfeometry

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

Introduction of Introduction of Seismic Interfeometry Seismic Interfeometry (continued)(continued)

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

Introduction of Introduction of Seismic Interfeometry Seismic Interfeometry (continued)(continued)

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

Overburden

Target

Introduction of Introduction of Seismic Interfeometry Seismic Interfeometry (continued)(continued)

• Seismic Interferometry:Seismic Interferometry:– Schuster & Rickett (1999)Schuster & Rickett (1999)– Schuster (2001)Schuster (2001)– Yu & Schuster (2001, 2006)Yu & Schuster (2001, 2006)– Jiang et al. (2005)Jiang et al. (2005)

• No restriction on source distribution

• Arbitrary velocity model

• Many types of events used

Introduction of Introduction of Seismic Interfeometry Seismic Interfeometry (continued)(continued)

• Seismic Interferometry Theory:Seismic Interferometry Theory:

Introduction of Introduction of Seismic Interfeometry Seismic Interfeometry (continued)(continued)

• Migration of VSP Multiples:Migration of VSP Multiples:

Introduction of Introduction of Seismic Interfeometry Seismic Interfeometry (continued)(continued)

• Successful Applications:Successful Applications:

Xiao, et al. (2005)

UTAM report

Drilling …

3D

Introduction of Introduction of Seismic Interfeometry Seismic Interfeometry (continued)(continued)

• Robust Imaging:Robust Imaging:Kirchhoff Migration

Interferometric Migration

KM

IM

Overburden

Introduction of Introduction of Seismic Interfeometry Seismic Interfeometry (continued)(continued)

• Super Resolution:Super Resolution:

Kirchhoff Migration Interferometric Migration

VSP salt flank imaging

HSP imaging

VSP multiple migration

CDP multiple migration

Salt Dome

Introduction of Introduction of Seismic Interfeometry Seismic Interfeometry (continued)(continued)

Various applications:

overburden

OutlineOutline

• AcknowledgementsAcknowledgements

• Introduction of Seismic InterferometryIntroduction of Seismic Interferometry

• Wave-equation Interferometric MigrationWave-equation Interferometric Migration– 3D Migration of VSP Multiples3D Migration of VSP Multiples– Salt Flank ImagingSalt Flank Imaging

• Conclusion & Technical ContributionsConclusion & Technical Contributions

Wave-Equation Interferometric Wave-Equation Interferometric Migration (WEIM): Migration (WEIM): considerationconsideration

Kirchhoff Migration Costs:1) Crosscorrelation2) Ray tracing3) Storage for traveltime tables

For Example: To obtain 85 x 87 x 1400

migrationcube, ~300 GB disk is required.

IVSP

WEIM: WEIM: theorytheory

WEIM costs for one gather:1) One wavefield

extrapolation2) One ray tracing3) One traveltime table

IVSP

Line-source Ray TracingLine-source Ray Tracing

Knownmedium

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 Multiples3D WEIM of VSP Multiples

2D Synthetic Test2D Synthetic Test

Offset (m)0 6000

Dep

th (

m)

0

4000

Offset (m)0 6000

Tim

e (s

)

0

5

Synthetic model Synthetic data

12 geophpnes

600 shots

Multiples

Migration ComparisonMigration Comparison

Offset (m)0 6000

Dep

th (

m)

0

4000

Migration of primaries Migration of multiples

Offset (m)0 6000

Dep

th (

m)

0

4000

Field Data ApplicationField Data Application

Survey GeometrySurvey Geometry

Each geophone grouphas 12 geophones.

~ 11 km

~ 11 km

~ 5 km deep

3 similar spirals,each correspondingto an offset-edgeophone group.

3D WEIM Result3D WEIM ResultMigration of only one receiver gather

Slice MovieSlice MovieMigration of only one receiver gather

Slice of 3D Migration CubeSlice of 3D Migration Cube

Offset (m)0 11000

Dep

th (

m)

0

6500

Common Image GatherCommon Image Gather

Offset (m)1 36

Dep

th (

m)

0

6500

VSP Salt Flank ImagingVSP Salt Flank Imaging

? 98 geophones

120 shots

Overburden

Interferometric Migration Interferometric Migration ResultResult

A Synthetic ExperimentA Synthetic Experiment

94 geophones

10 shots

Overburden

A Shot GatherA Shot Gather

WEIM Result (one shot)WEIM Result (one shot)

Offset (m)

0 1700

Dep

th (

m)

2700

5500

Artifacts

WEIM Result (ten shots)WEIM Result (ten shots)

Offset (m)

0 1700

Dep

th (

m)

2700

5500

OutlineOutline

• AcknowledgementsAcknowledgements

• Introduction of Seismic InterferometryIntroduction of Seismic Interferometry

• Wave-equation Interferometric MigrationWave-equation Interferometric Migration– 3D Migration of VSP Multiples3D Migration of VSP Multiples– Salt Flank ImagingSalt Flank Imaging

• Conclusion & Technical ContributionsConclusion & Technical Contributions

ConclusionConclusion

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

• However, the relatively weak energy However, the relatively weak energy waves and low fold imaging in some waves and low fold imaging in some applications could result in the low applications could result in the low S/N ratio of the image.S/N ratio of the image.

Technical Contributions (I)Technical Contributions (I)

• Wave-equation interferometric migration Wave-equation interferometric migration is proposed for efficient 3D migration of is proposed for efficient 3D migration of VSP multiples.VSP multiples.– It is as robust to velocity estimation errors as It is as robust to velocity estimation errors as

surface seismic imaging.surface seismic imaging.– It is much more cost efficient than surface It is much more cost efficient than surface

seismic surveys in obtaining a 3D subsurface seismic surveys in obtaining a 3D subsurface image volume.image volume.

– It might be also useful for time-lapse (4D) It might be also useful for time-lapse (4D) seismic monitoring for some oil fields.seismic monitoring for some oil fields.

Technical Contributions (II)Technical Contributions (II)

• Apply interferometric migration to Apply interferometric migration to salt flank imaging with VSP data:salt flank imaging with VSP data:– A huge chunk of overburden is ignored, A huge chunk of overburden is ignored,

so that the imaging is not only efficient, so that the imaging is not only efficient, but also robust to velocity estimation but also robust to velocity estimation errors.errors.

– Other vertical structures, such as faults Other vertical structures, such as faults that are difficult to image by surface that are difficult to image by surface seismic surveys could also be imaged.seismic surveys could also be imaged.

The EndThe End

Thank you.Thank you.

Ray DistributionRay Distribution

CDP ray distribution VSP ray distribution

Migrating Missed Near-offset Migrating Missed Near-offset TracesTraces

Missed near-offset traces due to limited acquisition.

Some of the missed near-offset traces can be migrated in the migration of multiples.

Synthetic TestSynthetic Test

Offset (m)0 5000

Depth (m)

0

1500

300 m20 m 20 m

Migration of PrimariesMigration of Primaries

Offset (m)0 5000

Depth (m)

0

1500

Migration of MultiplesMigration of Multiples

Offset (m)0 5000

Depth (m)

0

1500

Migration of Field Data Migration of Field Data PrimariesPrimaries

Offset (m)0 26000

Depth (m)

0

3500

Shortest offset=262 m; Shot and geophone spacing=25 m

Migration of Field Data Migration of Field Data MultiplesMultiples

Offset (m)0 26000

Depth (m)

0

3500