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Chapter 4.5-4.6

《Quantitative Seismic Interpretation》. Chapter 4.5-4.6. Fang Li 04-17-2009. Outline. Forward seismic modeling Future directions in quantitative seismic interpretation References. Forward seismic modeling. What?

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Chapter 4.5-4.6

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  1. 《Quantitative Seismic Interpretation》 Chapter 4.5-4.6 Fang Li 04-17-2009

  2. Outline • Forward seismic modeling • Future directions in quantitative seismic interpretation • References

  3. Forward seismic modeling • What? • Seismic modeling is essentially the construction of geologic computer models and simulating their seismic wave propagation response. • Why ? • Forward modeling of geophysical data is a tool used as a survey design aid and to constrain the interpretation of recorded/processed seismic data.

  4. When? • Before and after the acquisition of seismic field data. • Where? • Laboratory • Computer • Solve the equation of motion for seismic waves; Newton’s second law of motion; Constitutive relation, such as Hooke’s law;

  5. How?

  6. Methods • Convolution model • Reflectivity method • Ray tracing • Gaussian beams method • Finite difference method • Finite element method • Pseudo spectral method Ray Theory Wave Theory

  7. Convolution model 1> WAVELET * NI 2> Migrated seismic profile 3> Simplest & Useful 4> Far more including all Multiples, converted Waves, and attenuation Effects;

  8. From Neil Anderson (2002)

  9. Reflectivity method • For the creation of the complete elastic body-wave responses from a horizontally layered system; • Including all possible multiples,mode conversions ,and transmission losses.

  10. With multiples Without multiples PP SS From CREWES Research Report-Vol16(2004)

  11. Ray tracing • 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.

  12. From CREWES 2004 Class 2 AVO Class 1 AVO

  13. Finite difference method(FD) • The finite-difference method is powerful and flexible in accounting for complex non-homogeneities and arbitrary anisotropy of a medium; • Produce full wavefield; • Proper for complicated structures; • Involving grid dispersion and edge effects;

  14. From Yongyi Li (2007)

  15. Summary • 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.

  16. Future directions in quantitative seismic interpretation • More rigorous modeling and inversion of the wave propagation phenomena; • Combing sedimentologic and diagenetic modeling with rock physics modeling to obtain more realisticpredictions of seismic properties;

  17. Probabilistic Monte Carlo simulations to captureuncertaintiesin both rock physics and inversion results; • Incorporation of geostatistical methods to account for spatial correlations in reservoir properties;

  18. References • 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

  19. Thank you !!Have a good day!

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