VSP->Xwell Interferometry
description
Transcript of VSP->Xwell Interferometry
VSP->Xwell InterferometryVSP->Xwell Interferometry
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3x3 Classification Matrix3x3 Classification Matrix
SSPSSP VSPVSP SWPSWP
VSPVSP
SSPSSP
SWPSWP
SSPSSP SSPSSP SSPSSP SSPSSPVSPVSP SWPSWP
VSPVSP VSPVSP VSPVSP
SWPSWP SWPSWP SWPSWP
VSPVSP
SWPSWP
SWPSWP
VSPVSP
SSPSSP
SSPSSP
XwellXwell XwellXwell XwellXwell XwellXwellSSPSSP VSPVSP XwellXwell
VSP->Xwell TransformVSP->Xwell Transform
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G(B|x)G(B|x)
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G(A|x)G(A|x)
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G(A|x)*G(A|x)*oo
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Model basedModel basedNeeds V(x) around wellNeeds V(x) around well
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VSP ExperimentVSP Experiment
Problem:Problem: Overburden+statics defocus VSP migration Overburden+statics defocus VSP migration
Redatum sources below overburdenRedatum sources below overburden
Local VSP migrationLocal VSP migration
Solution:Solution: VSP -> Xwell Transform VSP -> Xwell Transform
MotivationMotivation
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VSP ExperimentVSP Experiment
(a) VSP data: P(g|s)=T(g|s)+R(g|s)
T(g|s)
s
gR(g|s)
x
s
(b) Backward reflection
R(g|s)g
x
R(x|s)= G(x|g)*R(g|s)g
(c) Backward transmission
T(g|s)
s
g
x
T(x|s)= G(x|g)*T(g|s)
g
(d) Crosscorrelation
m(x)= R(x|s) T(x|s)*g
Theory
Local VSP Green’s function
R(g|s)g
x
Key Idea of Local RTMKey Idea of Local RTM
Numerical ResultsNumerical Results
1. Synthetic VSP (Jinahua Yu) 1. Synthetic VSP (Jinahua Yu)
3. GOM VSP3. GOM VSP
2. Synthetic VSP (Xiang Xu) 2. Synthetic VSP (Xiang Xu)
0 km0 km
2 km2 km0 km0 km 3 km3 km
Walkaway VSPWalkaway VSP
Source number: Source number: 100100Shot interval: Shot interval: 10 m10 mReceiver number: Receiver number: 9191Receiver interval: Receiver interval: 10 m10 mDepth of the first receiver: Depth of the first receiver: 950 m950 mDepth of the last receiver: Depth of the last receiver: 1850 m1850 mTemporal interval: Temporal interval: 0.001 s0.001 s
Local VSP Migration ImageLocal VSP Migration Image
No Overburden velocity neededNo Overburden velocity needed
No need to know source location or excitation timeNo need to know source location or excitation time
X (m)X (m) 1400140010001000
950
1950
Dep
th (
m)
X (m)X (m) 1400140010001000
LimitationsLimitations
Rotated Pyramid vs PyramidRotated Pyramid vs PyramidLocal VSPLocal VSP Traditional VSPTraditional VSP
LL
DD
Numerical ResultsNumerical Results
1. Synthetic VSP (Jinahua Yu) 1. Synthetic VSP (Jinahua Yu)
3. GOM VSP3. GOM VSP
2. Synthetic VSP (Xiang Xu) 2. Synthetic VSP (Xiang Xu)
Sigsbee P-wave Velocity ModelSigsbee P-wave Velocity Model0
Dep
th (
km)
9.2
4500
1500
m/s
-12.5 12.5Offset (km)
279 shots
150 receivers150 receivers
Local Reverse Time Migration ResultsLocal Reverse Time Migration Results
4.6
9.2
Dep
th (
km)
-3 3Offset (km)
True modelMigration image
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Numerical ResultsNumerical Results
1. Synthetic VSP (Jinahua Yu) 1. Synthetic VSP (Jinahua Yu)
3. GOM VSP3. GOM VSP
2. Synthetic VSP (Xiang Xu) 2. Synthetic VSP (Xiang Xu)
Dep
th
(m)
Offset (m)4878
0 1829
0
GOM VSP Well and Source LocationGOM VSP Well and Source LocationSource @150 m offset
2800 m
3200 m
Salt
82 receivers
P-to-S ratio = 2.7
Velocity ProfileVelocity ProfileS WaveP Wave
Dep
th
(m)
0
45000 5000 0 5000
2800 m
3200 m
Salt
Incorrect velocity model
P-to-S ratio = 1.6
Velocity (m/s) Velocity (m/s)
Z-Component VSP DataZ-Component VSP DataD
epth
(m
)
Traveltime (s)
2652
3887
1.2 3.0
Salt
Direct P
Reflected P
Reverberations
X-Component VSP DataX-Component VSP DataD
epth
(m
)
Traveltime (s)
2652
3887
1.2 3.0
Salt
Direct P
Reflected P
Reverberations Direct S
Local Reverse Time Migration ResultLocal Reverse Time Migration Result
(1)
(2)
(3)
(1) specular zone, (2) diffraction zone, (3) unreliable zone
3.3
Dep
th (
km)
3.9
0 100Offset (m)
39receivers
reflectivity
ConclusionsConclusions
• VSP->XWell transform alternative to VSP_>SWPVSP->XWell transform alternative to VSP_>SWP
and VSP->SSP transformsand VSP->SSP transforms
• Source statics eliminated, no need to know src. Source statics eliminated, no need to know src. Location or excitation timeLocation or excitation time
• Local v(x) needed, overcomes defocusing due to Local v(x) needed, overcomes defocusing due to overburdenoverburden
• Not battle-field tested, needs decon probably, weird Not battle-field tested, needs decon probably, weird resolution characteristicsresolution characteristics