3-D Prestack Migration Deconvolution Bob Estill ( Unocal) Jianhua Yu (University of Utah)

Why 3-D Prestack MD ? Outline Migration Deconvolution Examples Conclusions Synthetic and field data

Why 3-D Prestack MD? Outline Migration Deconvolution Examples Conclusions Synthetic and field data

Limited recording aperture Aliasing problem Multi-illumination angles More 3-D prestack data Why 3-D Prestack MD

Migration noise and artifacts Migration Noise Problems Depth (km) Weak illumination Footprint

Purpose of 3-D MD: Improving spatial resolution Enhancing illumination Suppressing migration noise and artifacts

Migration Deconvolution Outline Why 3D Prestack MD ? Examples Conclusions Synthetic and field data

m’ = L d T Migration: but d = L m Migrated image Data L m Migration image = Blurred image of true reflectivity model m L is modeling operator Reflectivity

T m = (L L ) m’ 3-D Prestack MD Reflectivity Design an improved MD filter Migrated Section An improved MD operator aims at improving the stability of MD filter

Examples Migration Deconvolution Outline Conclusions Synthetic and field data Why 3D Prestack MD?

Examples Migration Deconvolution Outline Conclusions Synthetic and field data Why 3D Prestack MD?

Recording Geometry : Sources : Receivers

Recording Geometry 10 KM

0 3 X (km) 0 3 Y (km) 0 3 X (km) 0 3 Y (km) 0 3 X (km) 0 3 Y (km) 0 3 X (km) 0 3 Y (km) 0 3 X (km) 0 3 Y (km) 0 3 X (km) 0 3 Y (km) MIG MD Z=1 km Z=3 km Z=5 km Depth Slices

0 3 X (km) 0 3 Y (km) 0 3 X (km) 0 3 Y (km) 0 3 X (km) 0 3 Y (km) 0 3 X (km) 0 3 Y (km) 0 3 X (km) 0 3 Y (km) 0 3 X (km) 0 3 Y (km) MIG MD Z=7 km Z=9 km Z=10 km Depth Slices

0 2.5 km 0 Meandering Stream Model 2.5 km 5 X 1 Sources; 11 X 7 Receivers

Mig MD Model 0 Y (km) X (km) Z=3.5 KM

km 0 3-D SEG/EAGE Salt Model 12.2 km 9 X5 Sources; dxshot=dyshot=1 km 201 X 201 Receivers Imaging: dx=dy=20 m

3-D SEG/EAGE Salt Model Y=3.12 km X (km)Y (km)

Mig and MD ( Inline, negative polarity) X (km) Depth (km) X (km) MDMig

3-D SEG/EAGE Salt Model X (km)Y (km) Y=7.12 km

Mig and MD ( y=7.12 km, negative polarity) X (km) Depth (km) X (km) MDMig

3-D SEG/EAGE Salt Model X=8.12 km X=6.12 km

Mig and MD (x=6.12 km, negative polarity) Y (km) Depth (km) 5105 Y (km) MDMig

3-D SEG/EAGE Salt Model 1.4 km

Mig and MD ( z=1.4 km, negative polarity) X (km) 3 10 Y (km) X (km) MDMig

3-D SEG/EAGE Salt Model km

MD (z=1.2 km)Mig (z=1.2 km) X (km) 3 10 Y (km) X (km)

MD (z=1.2 km)Mig (z=1.2 km)

MD (z=1.4 km)Mig (z=1.4 km) X (km) 3 10 Y (km) X (km)

Migration Deconvolution Outline Examples Conclusions Synthetic and field data Why 3D Prestack MD?

Unocal Alaska 3-D Data : Receivers : Sources

Horizontal Slice at 1.2 s Inline Crossline 3D PSTM (courtesy of Unocal)MD

1.6 s Inline Crossline Horizontal Slice at 1.6 s 3D PSTM (courtesy of Unocal)MD

2.0 s Crossline Horizontal Slice at 2.0 s 3D PSTM (courtesy of Unocal)MD

2.0 s Inline Crossline Horizontal Slice at 2.4 s 3D PSTM (courtesy of Unocal)MD

3 Mig in Inline (Courtesy of Unocal) MD

Mig MD Mig MD

Migration Deconvolution Outline Why 3D Prestack MD? Examples Conclusions Synthetic and field data

Conclusions Improve resolution and mitigate some migration artifacts Suitable for Kirchhoff and Wave equation migration images Poststack MD processing = Postmig (up to Prestack MD processing <= Premig

Conclusions Improve resolution and mitigate some migration artifacts Suitable for Kirchhoff and Wave equation migration images Poststack MD processing = Postmig Prestack MD processing <= Premig ( relative with the specific MD filter )

Acknowledgments Thank Bob Estill and Unocal for providing the proprietary data set and the careful guidance of Unocal people in processing and interpreting Unocal Alaska dataThank Bob Estill and Unocal for providing the proprietary data set and the careful guidance of Unocal people in processing and interpreting Unocal Alaska data Thank 2002 UTAM sponsors for the financial supportThank 2002 UTAM sponsors for the financial support