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Coda Wave Interferometry (CWI) for Time-Lapse Monitoring in Rock Physics

Novel use of Coda Wave Interferometry (CWI) for monitoring velocity changes in complex media, with experimental applications in rock physics including density and velocity variations. CWI shows sensitivity to temperature and stress changes, offering a clear response compared to traditional methods. The method offers a more accurate representation of medium properties and has potential applications in understanding rock deformation behaviors.

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Coda Wave Interferometry (CWI) for Time-Lapse Monitoring in Rock Physics

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  1. Coda Wave Interferometry (CWI) for Time-Lapse Monitoring Jonathan Singh (jonathan.singh@ed.ac.uk) A Curtis, I Main, A Cartwright-Taylor, I B Butler, M Chapman, F Fusseis Subsidiary of Royal Dutch Shell

  2. Outline • What is the Velocity? • CWI for Monitoring Velocity Change • Experimental Rock Physics Applications

  3. Velocities in Complex Media High X ray density 760 μm Low X ray density Berea Sandstone from Madonna et al 2013

  4. Digital Rock Physics Density & Velocity of Water Density & Velocity of Quartz 760 μm 4 4

  5. Digital Rock Physics Simulated Wavefield Source Wavelet: 35 MHz 760 μm 5

  6. Variations in apparent velocity Velocity calculated from the standard method is strongly dependent on the positions of the sources and receiver. 10 Calculated from first break arrival Velocity Variation from Mean (%) c v 0 c v -15 6 Receiver X Position

  7. Variations in apparent velocity Velocity calculated from the standard method is strongly dependent on the positions of the sources and receiver. 10 Calculated from first break arrival Velocity Variation from Mean (%) c v 0 20% c v -15 7 Receiver X Position

  8. What’s the velocity? Fast Marching Eikonal Solver (CREWES toolbox) ?straight ?????????? ????= 760 μm 8

  9. What’s the velocity? Fast Marching Eikonal Solver (CREWES toolbox) ?straight ?????????? ????= 760 μm 9

  10. What’s the velocity? Fast Marching Eikonal Solver (CREWES toolbox) ?straight ?????????? ????= 760 μm 10

  11. What’s the velocity? Fast Marching Eikonal Solver (CREWES toolbox) ?straight ?????????? ????= 760 μm 11

  12. What’s the velocity? Fast Marching Eikonal Solver (CREWES toolbox) ?straight ?????????? ????= 760 μm What’s the sample velocity? Velocity estimate is very different depending on where you measure 12

  13. Coda Wave Interferometry

  14. Coda Wave Interferometry

  15. Coda Wave Interferometry

  16. Coda Wave Interferometry Coda

  17. Coda Wave Interferometry

  18. Coda Wave Interferometry

  19. Coda Wave Interferometry Use time shift (ts) from cross correlation: Theory derived in Sneider 2006

  20. Coda Wave Interferometry ?? ?= −???? ? Theory derived in Sneider 2006

  21. Velocity vs Temperature Temperature measured from external thermocouple Velocity survey every minute 55 54 53 Temperature (C) 52 51 50 49 10cm 48 47 46 45 0 2 4 Time (min) 6 8 10 Halldale Sandstone

  22. Velocity vs Temperature Using First Arrivals Variation in velocity not resolved above noise Using CWI Clear and coherent velocity response

  23. Rock Deformation • Fine grained laminated carbonate • Effective Pressure : 45 MPa • Differential Stress: < 250 MPa

  24. Rock Deformation Strain rate = 10-5s-1 Stepped Velocity Response Stepped Stress Program for permeability measurements

  25. Rock Deformation First breaks fail to show stepped response

  26. Rock Deformation Hertz-Mindilin Model ? = ??ℎ

  27. Summary • Velocity is not representative for a medium • CWI sensitively samples the bulk properties • Clear response to temperature and effective stress • Code to be made available and Paper to be submitted

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