Seismic scattering attenuation and its applications in seismic imaging and waveform inversion

1. Seismic scattering attenuation and its applications in seismic imaging and waveform inversion Yinbin Liu Vancouver Canada

2. 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

3. Outlines Introduction Low frequency scattering resonance Discussions

4. Anderson wave localization Wave in impurity band conduction Incident pulse 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 Random arrangements of electronic or nuclear spins Energy space distribution Common wave phenomenon: mechanical wave, electromagenetic wave, matter wave energy trap within low velocity zone multiple scattering

5. Interference and absorption Shale Sandstone shale Absorption has very little inference on signal

6. Gas reservoir: strong local heterogeneity Macroscope thin CBM Rock physics Well log fractures microscope Modified from Einsel,1992 Well log (rock physics) seismic response

7. 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

8. Gas-bearing formation Strong heterogeneity : multiple scattering Microscopic scale heterogeneity has an important influence on seismic response Effective media and Diffusive approximation

9. Low frequency earthquake A high frequency small-amplitude onset superposing on a low-frequency large-amplitude background

10. 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

11. Similarity of different wave fields Ocean wave Microwave dispersion Pleshko and Palocz, 1969 Hyper-Airy function

12. Fundamental laws Z1 Z1 Z2 Z2 Z1 Interference exactly include multiple scattering

13. Two scatterers (m and l)

14. 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

15. Seismic scale effects M=1 M=2 M=3 M=256 …… …… 512 layers 2 layers 4 layers 6 layers Ray Scattering A quasi-periodic layered model

16. Comparison between theory and experiment 10 MHz

17. Scale-dependent multiple scattering ray Low frequency coda enhancement effective dispersion

18. Multiple scattering Ray theory: large scale slowing velocity Multiple low frequency scattering theory resonance coherent scattering enhancement Effective medium theory: micro-scale Inhomogeneous scale

19. Physical explanation for dispersion v=D/t The direct waverapidly reduces to negligible values and the multiple reflection wavebecomes the first arrival. Liu and Schmitt, 2002

20. Physical interpretation 3 1 2 2+3+… (scattering resonance) 1 Coda

21. 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

22. Thank you for your attention