x (m) 1000 950 1950 depth (m) kirchhoff vs crosscorrelation migration 0.5 km 2.5 km 0.5 km 2.5 km...
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Kirchhoff vs Crosscorrelation Kirchhoff vs Crosscorrelation MigrationMigration
0.5 km
2.5 km0.5 km 2.5 km
0.5 km
2.5 km0.5 km 2.5 km
Kirchhoff Mig.Kirchhoff Mig. Crosscorr. Mig.Crosscorr. Mig.
Kirchhoff vs Crosscorrelation Kirchhoff vs Crosscorrelation MigrationMigration
0.5 km
2.5 km0.5 km 2.5 km
0.5 km
2.5 km0.5 km 2.5 km
Kirchhoff Mig.Kirchhoff Mig. Crosscorr. Mig.Crosscorr. Mig.
VSP Images withVSP Images withStatic ErrorsStatic Errors
0.5 km
2.5 km0.5 km 2.5 km
0.5 km
2.5 km0.5 km 2.5 km
Kirchhoff Mig.Kirchhoff Mig. Crosscorr. Mig.Crosscorr. Mig.
VSP Images withVSP Images withStatic ErrorsStatic Errors
0.5 km
2.5 km0.5 km 2.5 km
0.5 km
2.5 km0.5 km 2.5 km
Kirchhoff Mig.Kirchhoff Mig. Crosscorr. Mig.Crosscorr. Mig.
Field RVSP Images withField RVSP Images withStatic ErrorsStatic Errors
0.0 km
.9 km0.0 km .12 km 0.0 km .12 km
Kirchhoff Mig.Kirchhoff Mig. Crosscorr. Mig.Crosscorr. Mig.
Enhancing Illumination Coverage of VSP by Crosscorrelation Migration
Jianhua Yu
Gerard T. Schuster
University of Utah
Interferometric Imaging
Outline Outline
Motivation
Crosscorrelation Migration
SEG/EAGE Model
2-D RVSP Field Data
Conclusions
Outline Outline
Motivation
Crosscorrelation Migration
SEG/EAGE Model
2-D RVSP Field Data
Conclusions
Problems with VSP Imaging Problems with VSP Imaging Quality? Quality?
Limited recording apertureLimited recording aperture
Narrow illumination coverageNarrow illumination coverage
Static errors at VSP well Static errors at VSP well caused by location errorscaused by location errors
Solution: Xcorr Migration of Ghost ReflectionsSolution: Xcorr Migration of Ghost Reflections
Widens illumination coverage VSP CDP
Solution: Xcorr Migration of Ghost ReflectionsSolution: Xcorr Migration of Ghost Reflections
Widens illumination coverage VSP CDP
Eliminates Rec. Statics: No Need to Know Rec. Location
Eliminates ~ ½ of the Raypath
Outline Outline
Motivation
Crosscorrelation Migration
SEG/EAGE Model
2-D RVSP Field Data
Conclusions
Crosscorrelation MigrationCrosscorrelation Migration
m(x) = (g, m(x) = (g, ss, t + t ), t + t )
gg ssxxgxgx
Kirchhoff Migration of CrosscorelogramsKirchhoff Migration of Crosscorelograms
ss
gg
ss ggss
Uninteresting Part of MediumUninteresting Part of Medium
How do you remove kinematic effects of propagatingHow do you remove kinematic effects of propagatingthrough unintersting parts of medium?through unintersting parts of medium?
Uninteresting Part of MediumUninteresting Part of Medium
{{MMTT
Pick Direct Arrival Time T and shift allPick Direct Arrival Time T and shift allTraces by T Traces by T
MM
MM
MM
Uninteresting Part of MediumUninteresting Part of Medium
Pick Direct Arrival Time T and shift allPick Direct Arrival Time T and shift allTraces by T Traces by T
MM
MM
MM
Uninteresting Part of MediumUninteresting Part of Medium
Shifting Traces Removes Kinematic EffectsShifting Traces Removes Kinematic EffectsOf Propagating through Uninteresting Parts of MediumOf Propagating through Uninteresting Parts of Medium
MM
Uninteresting Part of MediumUninteresting Part of Medium
Shifting Traces Removes Kinematic EffectsShifting Traces Removes Kinematic EffectsOf Propagating through Uninteresting Parts of MediumOf Propagating through Uninteresting Parts of Medium
MM
Shifting Traces Removes Kinematic EffectsShifting Traces Removes Kinematic EffectsOf Propagating through Uninteresting Parts of Medium.Of Propagating through Uninteresting Parts of Medium.
..
MM
MM MM
m(x) = (g, t + t )m(x) = (g, t + t )
gxgx gg MMxxgxgx
Kirchhoff Migrate psuedo-shot gathersKirchhoff Migrate psuedo-shot gathers
gg
Source Moved to SurfaceSource Moved to Surface
Can replace time-shifted traces by crosscorrelogramsCan replace time-shifted traces by crosscorrelograms
Interferometric SummaryInterferometric Summary
??
Above SourceAbove SourceImagingImaging {{
Wider CoverageWider Coverage
VSPVSP
Wider, taller coverage. Eliminates Wider, taller coverage. Eliminates well statics and uninteresting parts of well statics and uninteresting parts of the medium.the medium.
Above SourceAbove SourceImagingImaging {{
Wider CoverageWider Coverage
VSPVSP
Interferometric SummaryInterferometric SummaryWider, taller coverage. Eliminates Wider, taller coverage. Eliminates well statics and uninteresting parts of well statics and uninteresting parts of the medium.the medium.
MM MM
m(x) = (g, t + t )m(x) = (g, t + t )
gxgx gg MMxxgxgx
Kirchhoff Migrate psuedo-shot gathersKirchhoff Migrate psuedo-shot gathers
Outline Outline
Motivation
Crosscorrelation Migration
SEG/EAGE Model
2-D RVSP Field Data
Conclusions
Well
2
0D
epth
(k
m)
0 3X (km)
SEG/EAGE Model
256 Sources
V = 1.5 - 3.0 km/s
Well
2
0D
epth
(k
m)
0 3X (km)
Receiver interval: 10 m
Receiver depth range: 0.1 -1 km
Receiver number: 91
Sample interval: 1 ms
Recording length: 3 s
Well location: (1.5 km, 0 km)
Source interval: 10 m
Source number: 256
Acquisition Parameters:
1 km
Tim
e (s
)
3
00.2 0.9Depth (km)
CSG 160
Tim
e (s
)
3
00.2 0.9Depth (km)
Ghosts (CSG 160)
Tim
e (s
)
3
00 2.4X (km) 1.4 2.4X (km)
Xcross 60CRG 60
2.0
0.5
Dep
th (
km
)
0.5 2.5X (km)
Kirchh Mig (45) Xcorr Mig (45) Xcorr. Mig(15’)
2.52.5 0.5 0.5
Sta
tic
erro
rs (
ms)
-50
500 900Well Depth (m)
Raw Data
Static Errors at Well
2.0
0.5
Dep
th (
km
)
0.5
Kirchhoff MigrationStatic Error: 0
X (km)
Static Error: 25 ms
2.5
Static Error: 50ms
2.52.5 0.5 0.5
2.0
0.5
Dep
th (
km
)
0.5
Crosscorrelation MigrationStatic Error: 0
X (km)
Static Error: 25ms
2.5
Static Error: 50 ms
2.52.5 0.5 0.5
Velocity ModelVelocity Model Primary vs Multiple ImagePrimary vs Multiple Image
00
111100 1616 00 1616X (km)X (km) X (km)X (km)
Dep
th (k
m)
Dep
th (k
m)
Contents Contents
Motivation
Crosscorrelation Imaging Condition
SEG/EAGE Model
2-D RVSP Field Data
Conclusions
Tim
e (s
)
0.3
030 900Depth (ft)
Raw Data(CRG15)
Tim
e (s
)
0.3
030 900Depth (ft)
Ghosts
5 24Trace No.
Tim
e (s
)
1.2
0.2 xcorr data (muted)
Tim
e (s
)
1.4
0.55 24Trace No.
Field Data (CSG 25)
Raw data (muted)
Master trace Master trace
Dep
th (
ft)
1300
2000 400X (ft) 0 400X (ft)
Standard mig Xcorr. mig
Dep
th (
ft)
1100
0
Standard Well data Xcorr.
Exxon Data
Outline Outline
Motivation
Crosscorrelation Migration
SEG/EAGE Model
2-D RVSP Field Data
Conclusions
Crosscorrelogram Migration Conclusions Crosscorrelogram Migration Conclusions
Eliminate the static errors in the well
No need to know source (RVSP) or receiver location (VSP)
Half sensitivity to velocity migration errors than mult. migration by “mirrors”.
Increased illumination coverage in the VSP image. VSP ->CDP
Conclusions Conclusions Loss of some lateral resolution?
Be careful about virtual multiple
Xcorr
Narrow Angle
Kirchhoff
Wide Angle
vs
Ghost is weaker than primaryExtra summation compared to KM
AcknowledgmentsAcknowledgments
UTAM sponsorsUTAM sponsors
Exxon for 2-D field dataExxon for 2-D field data
J. Claerbout + J. RickettJ. Claerbout + J. Rickett
II evolved from daylight II evolved from daylight imagingimaging
Dep
th (
ft)
1300
2000 400X (ft) 0 400X (ft)
Standard mig Xcorr. mig
Geological ModelGeological Model0 4
0
3
Dep
th(k
m)
X(km)
(2001)(2001)
Migration Result Using Crosscorrelation ImagingMigration Result Using Crosscorrelation Imaging
1.6
0
2.2
Tim
e (s
)
2.1X (km)
Too simple?
Widen illumination?
If there are static errors in well?
Why Use Crosscorrelation Why Use Crosscorrelation Migration?Migration?
Widen the illumination coverage in the VSP image
VSP geometryEquivalent surface geometry
Xcorr
Seismic Ghost ReflectionSeismic Ghost Reflection
DirectDirect
GhostGhost
??Find R(x,z) but not know source locationFind R(x,z) but not know source location
DirectDirect
GhostGhost
1 2DirectDirect xx
DirectDirectxx
MasterMasterSeismic Ghost ReflectionSeismic Ghost ReflectionSeismic Interferogram: Correlate TracesSeismic Interferogram: Correlate Traces
t}
MM
m(x) = (g, t + t )m(x) = (g, t + t )
gxgx gg MMxxgxgxMM
Kirchhoff Migrate psuedo-shot gathersKirchhoff Migrate psuedo-shot gathers
GhostGhost Direct Direct has kinematics of primary reflectionhas kinematics of primary reflectionxx
MM
WellWell
SourceSource
ReceiverReceiver
Primary
Direct Wave
Ghost
RVSP
x
g
s xg
xg ' sg
'sg
Ghost Reflection Imaging ConditionGhost Reflection Imaging Condition:
'g
xgxgsg
''
sg
'sg
x
g
s xg
xg ' sg
'sg
After Crosscorrelation of Two Traces at After Crosscorrelation of Two Traces at Locations g & g’Locations g & g’
'g
xgxgsg
''
sg
'sg
'sg
x
g
s xg
xg '
After Crosscorrelation of Two Traces at After Crosscorrelation of Two Traces at Locations g & g’Locations g & g’
'g
xgxg
'
sg
'sg
x
g
s
After Crosscorrelation of Two Traces at After Crosscorrelation of Two Traces at Locations g & g’Locations g & g’
'g
xg
xg '
xgxg
'
sg
'sg
Recall Green’s TheoremRecall Green’s TheoremEvery Surface Point = Source PointEvery Surface Point = Source Point
xgxgsgg
''''
Why is there insensitivity to static errors in the well?
ssgsg
'''
xgxgxcorrg
''
s
g’ g
xStatic errors
''sg
xgxgsgg
''''
Crosscorrelogram MigrationCrosscorrelogram Migration
''')( )()( dgdgxgxgggDCorr xm
Migrated ImageMigrated Image
Crosscorrelograms
Crosscorrelation Crosscorrelation Imaging ConditionImaging Condition
Dep
th (
ft)
1100
0
Well data Xcorr. Migration
Field Data
Dep
th (
ft)
1100
0
Well data Standard Migration
Exxon Data