Transcript Yinbin Liu, Seismic scattering attenuation and its potential

Seismic scattering attenuation and
its applications in seismic imaging
and waveform inversion
Yinbin Liu
Vancouver Canada
Seismic imaging: mathematics
Wave localization: physics and geology
Oil and gas reservoir:
strongly-scattered inhomogeneous media
Low frequency scattering resonance
A new physical concept
passive seismic monitoring
and non-volcanic seismic tremor
Outlines
Introduction
Low frequency scattering resonance
Discussions
Anderson wave localization
Incident
pulse
Wave in impurity band conduction
Random arrangements
of electronic or nuclear spins
Energy space
distribution
Very few believed [localization] at the time,
and even fewer saw its importance; among
those who failed to fully understand it at
first was certainly its author. It has yet to
receiver adequate mathematical treatment,
and one has to resort to the indignity of
numerical simulations to settle even the
simplest questions about it.
-- Philip W. Anderson, Nobel lecture,
8 December 1977
Common wave phenomenon:
mechanical wave, electromagenetic wave, matter wave
energy trap within low velocity zone
multiple scattering
Interference and absorption
Shale
Sandstone
shale
Absorption has very little inference on signal
Gas reservoir: strong local heterogeneity
Macroscope
Rock physics
Well log
thin CBM
fractures
microscope
Well log
(rock physics)
Modified from Einsel,1992
seismic response
Seismic imaging resolution
Velocity = 3000 m/s
Dominant frequency 30 Hz
Wavelength = 3000 / 30 = 100 m
Reservoir thickness is usually much less
than wavelength
Only strongly-scattered reservoir can be
seen by seismic
Gas-bearing formation
matrix impedance 5.80 2.65

 87.8
gas impedance
0.7  0.25
Strong heterogeneity : multiple scattering
Microscopic scale heterogeneity has an important
influence on seismic response
Effective media and Diffusive approximation
Low frequency earthquake
A high frequency small-amplitude onset superposing
on a low-frequency large-amplitude background
Strongly-scattered small-scale heterogeneity
Media: gas-oil-bearing or magam geological bodies
-- strong microscopic-scale heterogeneity
Seismic response: macroscopic effect
Medium structure: microscopic scale
Model: coupling effect (mecroscopy)
it is still a challenge project in physics
Similarity of different wave fields
Ocean wave
Microwave dispersion
Pleshko and Palocz, 1969
Hyper-Airy function
Fundamental laws
Z1
Z1
Z2
Z2
Z1
Interference
exactly include multiple scattering
Two scatterers (m and l)
Multiple scattering theory
Systematic perturbation theory (T matrix)
Twesky multiple scattering theory
Above two theories are not suitable for studying
the high order multiple scattering in strongly
scattered scale-small heterogeneity
Convergence issue
Seismic scale effects
M=1
M=2
M=3
M=256
……
2 layers
Ray
4 layers
6 layers
……
512 layers
Scattering
A quasi-periodic layered model
15
Comparison between theory and experiment
1.5
C alculation
Amplitude
1.0
E xperim ent
0.5
0.0
-0.5
-1.0
10 MHz
-1.5
0
1
2
3
4
5
tim e , u s
6
7
8
Scale-dependent multiple scattering
ray
Low frequency
coda
enhancement
effective
dispersion
Multiple scattering
Ray theory: large scale
slowing velocity
Multiple
low frequency scattering
theory
resonance
coherent scattering
enhancement
Effective medium theory: micro-scale
Physical explanation for dispersion
v=D/t
The direct wave rapidly reduces to negligible values and the
multiple reflection wave becomes the first arrival.
Liu and Schmitt, 2002
Physical interpretation
3
1
2
2+3+… (scattering resonance)
1
Coda
Impact on wave imaging
The frequency of LFSR, which is about one order of
magnitude lower than that of the natural resonance,
provides higher resolution.
Multiple scattering
Multiple correlation
Multiple iteration
Passive seismic monitoring (geophones are put in borehole)
Non-volcanic seismic tremor
Signal is no beginning and no ending
persisting for days and months
Thank you for your attention