Extracting 20 0 Hz Information from 50 Hz Data
description
Transcript of Extracting 20 0 Hz Information from 50 Hz Data
G. Schuster, S. Hanafy, and Y. Huang,
Extracting 200 Hz Information from 50 Hz Data
KAUSTRayleigh Resolution Profile Superresolution Profile
Sincfunction
Spikingfunction
Outline• Motivation: Why Resolution Matters• Diffraction vs Specular Resolution: Example• Evanescence Resolution• Field Test • Conclusions
Resolution Dx~l/2
L
Z
Δx
Depth
Rayleigh Resolution:
Abbe Resolution:
Super Resolution?:
Dx = lz 4L
Dx = l 2
Dx << l 2
Δx
KAUST yacht
0 km 7 km
0 km
3 km
0 km 7 km
Geophysical Resolution
(Jianhua Yu)
?
Transmission+Reflection Wavepaths(Woodward, 1992)
RTM Resolution: Dx=Rayleigh, Dz=l/4
RTM smile
FWI Resolution: ?
FWI rabbit ears
Z
X
d
Transmission+Reflection Wavepaths(Woodward, 1992)
FWI Resolution:
FWI rabbit earsd
Z
X
FWI Resolution: Dx = 2ld (Williamson, 1991)
3
Transmission+Reflection Wavepaths(Woodward, 1992)
FWI Resolution:
FWI rabbit ears
X
Diff. FWI Resolution: Dxdiff = ld
FWI Resolution: Dx = 2ld (Williamson, 1991) Dx Dxdiff
= 2
d
Benefit: Diffractions transformSSPXwell or VSP DataLiability: SNRdiff << SNRspec
3
Summary
FWI rabbit ears
Diff. FWI Resolution: Dxdiff = ld vs Specular FWI Resolution: Dx =
Benefit: Diffractions transform SSPXwell or VSP DataLiability: SNRdiff << SNRspec
Outline• Motivation: Why Resolution Matters• Diffraction vs Specular Resolution: Example• Evanescence Resolution• Field Test • Conclusions
Diffraction Waveform Modeling
Born
Modeling
0 Distance (km) 3.8
0D
epth
(km
)1.
20
Dep
th (k
m)
1.2
0tim
e (s
)4.
0
0 Distance (km) 3.8
Velocity
Reflectivity
Scattered CSG
Diffraction Waveform Inversion
0 Distance (km) 3.8
0D
epth
(km
)1.
20
Dep
th (k
m)
1.2
Initial Velocity
Estimated Reflectivity
0D
epth
(km
)1.
2
Inverted Velocity
0 Distance (km) 3.8
0D
epth
(km
)1.
2
True Velocity
Outline• Motivation: Why Resolution Matters• Diffraction vs Specular Resolution: Example• Evanescence Resolution• Field Test • Conclusions
Mig(z)
Far-field Propagation l-limited Resolutioneiwtxg
l
rG(g|x)=
Time
Mig(z)
Near-field Propagation l/20 Resolutioneiwtxg
l
rG(g|x)=
Time
Note: Time delay unable todistinguish 2 scatterers, butnear-field amplitude changes can: Dx=l/20
Mig(z)
r Evanescent energy
Near-field Propagation l/20 Resolutioneiwtxg
l
rG(g|x)=
Time
Note: Time delay unable todistinguish 2 scatterers, butnear-field amplitude changes can: Dx=l/20
Mig(z)
r Evanescent energy
If source is in farfield of scatterers& geophones in nearfield, superresolution possible
Summary
lTime
Mig(z)
1. Near-field Propagation l/20 Resolution
If source is in nearfield of scatterers& geophones in farfield, superresolution possible
reciprocity
If source is in farfield of scatterers& geophones in nearfield, superresolution possible
1. Near-field Propagation l/20 Resolution
Summary
lTime
Mig(z)
If source is in nearfield of scatterers& geophones in farfield, superresolution possible
reciprocity
If source is in farfield of scatterers& geophones in nearfield, superresolution possible
CRG
Outline• Motivation: Why Resolution Matters• Diffraction vs Specular Resolution: Example• Evanescence Resolution• Field Test • Conclusions
l
Near-Field Scatterer Images
l
Dx ~ 0.01l
ll
Dx ~ 0.1l
ll
Dx ~ 0.7l
D z ~ 0.1l
ll
25 Near-Field Scatterers Image
l
25 Near-Field Scatterers Image
Migration image at superresolution
l
25 Near-Field Scatterers Image
25 Near-Field Scatterers Image
Vp=1.5 km/sVs=0.75 km/s
Vp=3.0 km/sVs=1.5 km/s
100 m
40 m
Elastic Tunnel Test: 6 Near-Field Scatterers
S wave
P wave
Vp=1.5 km/sVs=0.75 km/s
Vp=3.0 km/sVs=1.5 km/s
100 m
Elastic Tunnel Test: 6 Near-Field Scatterers
S wave
P wave
40 m
No scatterer datascattered data
Outline• Motivation: Why Resolution Matters• Diffraction vs Specular Resolution: Example• Evanescence Resolution• Field Test • Conclusions
Experimental Setup(Not to Scale)Superresolution Test
Goal: Test superresolution imaging by seismic experiment
Experiment: Data with and without a scatterer
l=1.6 m
Experimental Setup(Not to Scale)Superresolution Test
Goal: Test superresolution imaging by seismic experiment
Experiment: Data with and without a scatterer
0.2 m0.6 m
l=1.6 m
TRM Profiles
l/4 Resolution (110 Hz)
w/o scatterer0.5 m
with scatterer
l/8 Resolution (55 Hz)
with scatterer
0.5 m
220 Hz information from 55 Hz data
Theory
l
Summary
• Workflow 1. Collect Shot gathers G(g|s ), separate scattered field 2. m(s’) = S G(g,t|s’)* G(g,t|s ) 3. TRM profiles
• Synthetic Results Dx~l/10
• Limitations Either src or rec in nearfield of subwavelength scatterer Scattered field separated from specular fields is Big Challenge
Diff. FWI Resolution: Dxdiff = ld vs Specular FWI Resolution: Dx =
Possible Applications
VSP: Find local anomalies, faults, and scatterer points around boreholes in VSP data
Ground
Borehole
SSP: Detect local anomalies, faults, and scatterer points around surface
Farfield?
Subduction zone
TRM Profile
Earthquakes along a Fault Detect Fault Roughness
Subduction zone
Earthquakes US Array Detect Near Surface
TRM Profile