Transcript Chapter 4.5-4.6

《Quantitative Seismic Interpretation》
Chapter 4.5-4.6
Fang Li
04-17-2009
Outline
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Forward seismic modeling
Future directions in quantitative seismic
interpretation
References
Forward seismic modeling
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What?
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Seismic modeling is essentially the construction
of geologic computer models and simulating
their seismic wave propagation response.
Why ?
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Forward modeling of geophysical data is a tool
used as a survey design aid and to constrain
the interpretation of recorded/processed
seismic data.
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When?
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Before and after the acquisition of seismic field
data.
Where?
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Laboratory
Computer
Solve the equation of motion for seismic waves;
Newton’s second law of motion;
Constitutive relation, such as Hooke’s law;
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How?
Dimensions
1D
2D
3D
Domains
Time
Frequency
Frequencywavenumber
Mappings
Cartesian
coordinates
Cylindrical
coordinates
Spherical
coordinate
Properties of
medium
Applications
Methods
Isotropy
Acoustic
Anisotropy
Elastic
Viscoelastic
Complex structural
(fracture, crack, pore space etc)
Next slide
Multi-phase
Stratigraphic
Methods
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Ray Theory
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Wave Theory
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Convolution model
Reflectivity method
Ray tracing
Gaussian beams method
Finite difference method
Finite element method
Pseudo spectral method
Convolution model
1> WAVELET * NI
2>
Migrated seismic profile
3> Simplest & Useful
4>
Far more including all
Multiples, converted
Waves, and attenuation
Effects;
From Neil Anderson (2002)
Reflectivity method
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For the creation of the complete elastic
body-wave responses from a horizontally
layered system;
Including all possible multiples,
mode conversions ,and
transmission losses.
Without multiples
With multiples
PP
SS
From CREWES Research Report-Vol16(2004)
Ray tracing
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Ray tracing can be used to compute seismic
wave travel times and amplitudes along ray
paths in a heterogeneous medium when the
frequency present in the wave are high
enough so that the ‘geometrical optics’
approximation can be used.
From CREWES 2004
Class 2 AVO
Class 1 AVO
Finite difference method(FD)
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The finite-difference method is powerful and
flexible in accounting for complex nonhomogeneities and arbitrary anisotropy of a
medium;
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Produce full wavefield;
Proper for complicated structures;
Involving grid dispersion and edge effects;
From Yongyi Li (2007)
Summary
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All modeling methods are rooted in the
same physical theory.
Each modeling method has specific
strengths and weaknesses.
Any particular method has limited ability to
represent this underlying physical reality.
Future directions in quantitative
seismic interpretation
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More rigorous modeling and inversion of the
wave propagation phenomena;
Combing sedimentologic and diagenetic
modeling with rock physics modeling to
obtain more realistic predictions of seismic
properties;
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Probabilistic Monte Carlo simulations to
capture uncertainties in both rock physics
and inversion results;
Incorporation of geostatistical methods to
account for spatial correlations in reservoir
properties;
References
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Krebes E.S. , Seismic forward modeling, CSEG
Recorder, 2004.
Margrave G.F, Seismic modeling: An essential
interpreter’s tool, CSEG 2004.
Anderson N., Forward seismic modeling: the key to
understanding reflection seismic and ground
penetrating radar(GPR) techniques, 2002.
Chopra S., Seismic elastic modeling, CSEG 2005
www.crewes.org
Thank you !!
Have a good day!