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Wavepath Refraction Migration on Near-Surface Refraction Data. Jianming Sheng. Outline. Motivation. Numerical Examples. Wavepath Refraction Migration. Summary. Motivation. Produce better seismic image by Traveltime Tomography + Refraction Migration.

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Presentation Transcript
outline
Outline
  • Motivation
  • Numerical Examples
  • Wavepath Refraction Migration
  • Summary
motivation
Motivation
  • Produce better seismic image by

Traveltime Tomography + Refraction Migration

  • Help to reduce the uncertainties in the tomograms.
outline1
Outline
  • Motivation
  • Numerical Examples
  • Wavepath Refraction Migration
  • Summary
refraction migration

G

S

Imaging Condition

T=TSX+TXY+TYG

X

Y

Refraction Migration
outline2
Outline
  • Motivation
  • Numerical Examples
  • Refraction Migration
  • Summary
numerical examples
Numerical Examples
  • 2D refraction data from INCO
  • 2D marine data from WesternGeco and ChevronTexaco
2d inco refraction data
2D INCO Refraction Data

Courtesy of Alan King

Shot spacing: 50 m

Shots: 105

Channel: 24

Receiver: 10 m

Length: 2.56 sec.

Sample: 0.625 ms

2025 traveltimes were picked

by Prof. Schuster

slide9

CSG #3

Residual vs. Iterations

0

55

Traveltime (sec.)

Traveltime (msec.)

0.26

0

220

Offset (m)

5

0

Iterations

40

traveltime tomogram
Traveltime Tomogram

3500

0

2500

Depth (m)

1500

500

150

(m/s)

0

Distance (m)

2000

ray density
Ray Density

200

0

140

Depth (m)

80

20

150

(m/s)

0

Distance (m)

2000

refraction migration1
Refraction Migration

5

0

Depth (m)

0

150

-5

0

Distance (m)

2000

tomogram refraction migration
Tomogram/Refraction Migration

3500

0

2500

Depth (m)

1500

500

150

(m/s)

0

Distance (m)

2000

numerical examples1
Numerical Examples
  • 2D refraction data from INCO
  • 2D marine data from WesternGeco and ChevronTexaco
gulf of mexico seismic line
Gulf of Mexico seismic line

Courtesy of Alan Leeds

Shot spacing: 25 m

Shots: 990

Channel: 180

Receiver: 25 m

Sample: 4 ms

Length: 8 sec.

A total of 86,736 traveltimes

were picked and inverted.

traveltime velocity tomogram
Traveltime Velocity Tomogram

0

2100

1900

Depth (m)

1700

1500

1000

(m/s)

5500

CDP NUMBER

6500

ray density refraction migration

0.60

2700

0.40

0.20

2000

0.00

-0.20

1300

-0.40

-0.60

600

-0.80

-1.00

Ray Density/Refraction Migration

0

Depth (m)

1000

5500

CDP NUMBER

6500

reflection migration
Reflection migration

0

Depth (m)

1000

5500

CDP NUMBER

6500

outline3
Outline
  • Motivation
  • Numerical Examples
  • Wavepath Refraction Migration
  • Summary
summary
Summary
  • Wavepath refraction migration method
  • was applied to two field data sets.
  • Refraction migration can help
  • reducing uncertainties in tomograms.
slide21

Acknowledgment

I thank the sponsors of the 2002 UTAM Consortium for their financial support . I thank Alan King and Alan Leeds for providing the data set and helpful instructions. I thank Prof. Schuster for picking the traveltimes.