Main Energy Fourier Finite Difference Migration

1
Main Energy Fourier Finite Difference Migration

• Jianhua Yu
• Department of Geology Geophysics
• University of Utah

2
Objective
? Improve computational efficiency of
wave-equation extrapolation ? Produce high
quality image of complex structure
3
Frequency domain migration
For each depth
Forward source wavefield extrapolation for each
frequency component
Backward receiver wavefield extrapolation for
each frequency component
Applying imaging condition
4
Main Energy FFD migration
For each depth
Forward source wavefield extrapolation for a few
frequency components
Capture main energy of source wavefield in time
domain at current depth
Transform back into frequency domain
Backward receiver wavefield extrapolation for
each frequency component
Applying imaging condition
5
Main Energy FFD migration
Strengths
Efficient forward extrapolation
Wider angle FFD operator can handle strong
velocity contrast and steep dip imaging
Less numerical anisotropy in 3D by applying high
order implicit FD algorithm
6
Summary
Wider angle 3D FFD is finished on zero-offset
SEG/EAGE data
Main Energy 3D FFD is being tested on prestack
SEG/EAGE data
7
2D Impulse Response
(Velocity contrast, i.e., V/Vmin 3.0)
X (km)
X (km)
0
4
0
4
0
Depth (km)
2.4
Standard wider angle FFD
Main energy wider angle FFD
8
Comparison of 3D Impulse Response
X (km)
0
4
0
FD algorithm
Depth (km)
2.4
0
Main energy wider angle FFD
Depth (km)
2.4
9
Snapshot of Forward Extrapolation for SEG/EAGE
Salt Model
X (km)
10
0
0
Standard Method
Time(s)
4
0
New Method
Time(s)
4
0
Captured Main Energy
Time(s)
4
10
Comparison of FFD and Main Energy FFD Migration
X (km)
0
4
0
FFD algorithm
Depth (km)
2.4
0
Main energy FFD (computational time saving about
38 )
Depth (km)
2.4