View
231
Download
4
Category
Tags:
Preview:
Citation preview
Seismic scattering attenuation and Seismic scattering attenuation and
its applications in seismic imaging its applications in seismic imaging and waveform inversionand waveform inversion
Yinbin LiuVancouver 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
Anderson wave localizationAnderson wave localization
Very few believed [localization] at the time,and even fewer saw its importance; amongthose who failed to fully understand it atfirst was certainly its author. It has yet toreceiver adequate mathematical treatment,and one has to resort to the indignity ofnumerical simulations to settle even the simplest questions about it.
-- Philip W. Anderson, Nobel lecture, 8 December 1977
Incident pulse
Energy space distribution
Wave in impurity band conduction
Common wave phenomenon: mechanical wave, electromagenetic wave, matter wave energy trap within low velocity zone multiple scattering
Random arrangements of electronic or nuclear spins
Interference and absorptionInterference and absorption
Absorption has very little inference on signal
ShaleSandstoneshale
Well log(rock physics)
Gas reservoir: strong local heterogeneityGas reservoir: strong local heterogeneity
thin CBM
Modified from Einsel,1992microscope
Rock physicsWell log
frac
ture
s
Macroscope
seismic response
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
Seismic imaging resolutionSeismic imaging resolution
Gas-bearing formationGas-bearing formation
Microscopic scale heterogeneity has an important influence on seismic response
8.8725.07.0
65.280.5
impedance gas
impedancematrix
Strong heterogeneity : multiple scattering
Effective media and Diffusive approximation
A high frequency small-amplitude onset superposing
on a low-frequency large-amplitude background
Low frequency earthquakeLow frequency earthquake
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
Strongly-scattered small-scale heterogeneityStrongly-scattered small-scale heterogeneity
Hyper-Airy function
Similarity of different wave fieldsSimilarity of different wave fields
Ocean wave
Microwave dispersion
Pleshko and Palocz, 1969
Multiple scattering theoryMultiple 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
15
Seismic scale effectsSeismic scale effects
A quasi-periodic layered model
……
M=1 M=2 M=3
……
2 layers 4 layers 6 layers
M=256
512 layers
Ray Scattering
Comparison between theory and experiment
0 1 2 3 4 5 6 7 8-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Calculation
Experiment
Am
plitu
de
time, us
10 MHz
Scale-dependent multiple scatteringScale-dependent multiple scattering
ray
effectivedispersion
coda
Low frequency
enhancement
Ray theory: large scale
slowing velocity
Multiple low frequency scattering
theory resonance
coherent scattering
enhancement
Effective medium theory: micro-scale
Inh
om
og
en
eou
s s
cal e
Multiple scatteringMultiple scattering
The direct wave rapidly reduces to negligible values and the multiple reflection wave becomes the first arrival.
Liu and Schmitt, 2002
v=D/t
Physical explanation for dispersionPhysical explanation for dispersion
The frequency of LFSR, which is about one order of magnitude lower than that of the natural resonance, provides higher resolution.
Multiple scatteringMultiple correlationMultiple 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
Impact on wave imagingImpact on wave imaging
Recommended