This document explores the application of multiple interferometry in vertical seismic profiling (VSP) to enhance the classification matrix for seismic data interpretation. Key points highlight the benefits of common raypath cancellation, the role of virtual sources, and the significance of summation over sources to enhance illumination areas. The methodology mitigates source statics, enabling efficient SSP transformation from VSP data. Examples from synthetic and field data illustrate the practical implications, reaffirming this innovative approach's efficacy in seismic imaging and analysis.
01 / 51Advanced VSP Multiple Interferometry for Effective SSP Data Processing and Analysis
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Advanced VSP Multiple Interferometry for Effective SSP Data Processing and Analysis
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Interferometry Summary G(A|x)* G(B|x) = G(A|B) x B A B B A A x x x ! k Key Point #1: Common Raypath Cancels Key Point #2: Every Bounce Pt on Surface Acts a New Virtual Source Key Point #3: Summation over Sources Picks out Specular Contribution Key Point #4: Kills Source Statics and no need to know src location or excitation time Key Point #5: Huge increase in Illumination Area
G(A|x)* G(B|x) = G(A|B) x Correlation Redatuming VSP ->SSP ! k Standard VSP Primary VSP -> SSP
o o S o S well S Reciprocity Correlation Equation Given: VSP data G(A|x) Find: SSP data G(A|B) A B x
n { } * * * S + S + S - G(A|x) = G(A|B) - G(B|A) G(B|x) G(A|x) G(B|x) x o k o o o o G(A|x)* G(B|x) = Im[G(A|B)] well 2 d x S o S well S Reciprocity Correlation Equation Given: VSP data G(A|x) Find: SSP data G(A|B) A B x
x k G(A|x)* G(B|x) = Im[G(A|B)] G(B|A) A B A B A B x x x Reciprocity Correlation Equation VSP => SSP Given: VSP data G(A|x) Find: SSP data G(A|B) G(A|x) G(B|x)*
Examples 1. 2D Synthetic VSP Data 2. 2D Field VSP Data 3. 3D VSP Data
Well 256 Sources V = 1.5 - 3.0 km/s 0 Depth (km) SEG/EAGE Model 2 0 X (km) 3
Acquisition Parameters: Well location: (1.5 km, 0 km) Source interval: 10 m Source number: 256 Receiver interval: 10 m Receiver depth range: 0.1 -1 km Receiver number: 91 Sample interval: 1 ms Recording length: 3 s Well 0 1 km Depth (km) 2 0 X (km) 3
VSP VSP SSP 1. FK Filter up and downgoing waves x x k G(A|x)* G(B|x) G(A|x)* = Im[G(A|B)] G(B|x) 2. Correlation: f(A,B,x) = f(A,B,x) 3. Summation: k = Im[G(A|B)] M(x) = Mig(G(A|B)) 4. Migration: A B A B A B x x x Implementation
Work flow Separate up and down going wavefields Upgoing wavefield Downgoing wavefield Statics Statics Statics Ray tracing Pick first-break Specular interferometry Primaries migration Multiples migration
Standard vs Interferometry Mig VSP (Narrow vs Wide Illumination) VSP Interferometry Imaging 1500 m VSP Primaries migration 1000 m 500 m 100 Time (ms) geophones 1600
Examples 1. 2D Synthetic VSP Data 2. 2D Field VSP Data: GOM Data 3. 3D VSP Data
Survey Geometry ~ 11 km ~ 11 km 3 similar spirals, each corresponding to an offset-ed geophone group. Each geophone group has 12 geophones. ~ 5 km deep
VSP->SSP Summary G(A|x)* G(B|x) = G(A|B) x B A B B A A x x x ! k Key Point #1: Common Raypath Cancels Key Point #2: Every Bounce Pt on Surface Acts a New Virtual Source Key Point #3: Summation over Sources Picks out Specular Contribution Key Point #4: Kills Source Statics and no need to know src location or excitation time Key Point #5: Huge increase in Illumination Area
VSP->SSP Caveats G(A|x)* G(B|x) = G(A|B) x B A B B A A x x x ! k 1. Infinitely source wide aperture. Artifacts must be recognized/fixed) 2. No attenuation assumed (remedy: attenuation compensation) 3. Be careful beneath salt domes (extra bounces get double defocused by salt). 3. Violation of assumptions seems ok for kinematics, not amplitudes
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