Migration Deconvolution Migration Deconvolution for VSP and Surface Datafor VSP and Surface Data

Jianhua YuJianhua Yu

Feb 3, 2005Feb 3, 2005

OutlineOutlineMotivation

Migration Deconvolution

Examples

Summary

OutlineOutlineMotivation

Migration Deconvolution

Examples

Summary

5

10

Dep

th (

km

)

WE Mig.

MD

Surface Seismic Migration and MD images

3D

VSP Data: VSP Data:

Irregular acquisition geometry

well

2D

Objectives : Objectives :

Improve spatial resolution

Enhance illumination

Suppress migration noise and artifacts

Develop migration deconvolution for VSP data

OutlineOutlineMotivation

Migration Deconvolution

Examples

Summary

mMigration Modeling

Migration image

RG GT

Reflectivity

Migration:

G GT -1

][ G GT -1

][RG GT m

Migration deconvolution:

mR G GT -1

][

Migration Green’s Function

sgsoogsgomig rdrdrrGrrGrrGrrGrr

)()()()()( **

MD image

Migration Deconvolution

)(~

),,~,(~

...,),,,~,(~

),,,~,(~

)(~21 inppippippii zkRzyxzkzyxzkzyxzkzkm

FFT of ),,,,( ippj zyxzyx

MigratedMigrated

datadata

m

True True ReflectivityReflectivity

R

Discrete Migration deconvolution

OutlineOutlineMotivationMigration deconvolution

Examples

Summary

VSP data

Surface seismic data

3 km

3 km

1.75 km

Nsx=Nsy=21, dsx=dsy=150 m

12 g

eoph

one

Ng=12, dgz=50 m

(750 m – 1300m)

VSP Geometry: source 21 x 21; geophone: 12

Depth=1.75 kmMigration MD

3 km

3 km

1.75 km

Nsx=Nsy=21, dsx=dsy=150 m

30 g

eoph

one

Ng=30, dgz=50 m

(100 m – 1500m)

Depth=1.75 km

Migration MD

OutlineOutlineMotivationMigration deconvolution

Examples

Summary

VSP data from salt model

Surface seismic data

750 m

21 g

eop

hon

es

7 km

16 km

320 shots

2D

Velocity

X (km)

Dep

th (

km)

Well

X (km)

Tim

e (s

)

10

0

0 15

CRG 21 (z=7.75 km)

(Courtesy of BP)

X (km)0 15

CRG 1 (z=7.0 km)

Primary Migration Image

X (km)

Dep

th (

km)

12

5

0 15

X (km)0 10

MDX (km)

Dep

th (

km

)

10

8

0 10

MIG

X (km)4 10

MDX (km)

Dep

th (

km

)

10

8

4 10

MIG

OutlineOutlineMotivationMigration deconvolution

Examples

Summary

vsp data

Surface seismic data

L500

Mig (Unocal) MD

X XT

ime

(s)

0.0

4.5

L500

Mig (Unocal) MD

X XT

ime

(s)

1.0

4.0

X10

Mig (Unocal) MD

Y YT

ime

(s)

1.0

5.0

X10

Mig (Unocal) MD

Y YT

ime

(s)

2.5

4.0

Inline 171

1 500Xline 1 500Xline

Tim

e (s

)

2.4

4

MIG (Unocal) MD

Mig MDYcross x=50T

ime

0.5

4.50 41Y (kft) 0 41Y (kft)

Mig MDYcross x=50T

ime

0.5

2.00 41Y (kft) 0 41Y (kft)

Mig MDXcross Y=125T

ime

0.5

4.50 12X (kft) 0 12X (kft)

Mig MDT

ime

2.5

4.5

Xcross Y=125

4 12X (kft) 4 12X (kft)

Xline 181

1 170Inline 1 170Inline

Tim

e (s

)

2.4

4

MDMIG (Unocal)

Xline 281

1 170Inline 1 170Inline

Tim

e (s

)

2.4

4

MDMIG (Unocal)

Mig MD

0

Z=3.0s

12.75X(kft) 0 12.75X(kft)

Y (

kft)

41

0

1 170Inline 1 170Inline

Xli

ne

1

550

MDMIG (Unocal)

3.4 s

1 170Inline 1 170Inline

Xli

ne

1

550

MDMIG (Unocal)

3.6 s

OutlineOutlineMotivationMigration deconvolution

Examples

Summary

VSP data from salt model

Surface seismic data

MD improves the resolution of VSP and surface migrated image partly

The cost depends acquisition geometry and filter length used

Summary

Time MD and poststack MD is more stable.

Summary

To reduce computational cost:

Analytic MD operator

Decimated acquisition geometry

Mig MD

Fre

q

0

120

Spectrum for Meandering Model

Mig MD

Fre

q

0

120

Spectrum for Unocal Data

AcknowledgementsAcknowledgements

UTAM Sponsors

BP, Unocal

Brian Hornby, Hans Sugianto

X10

Mig (Unocal) MD

Y YT

ime

(s)

1.0

5.0