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Advanced Wave Equation Migration Techniques for Enhanced Seismic Imaging at SEG 2005

This presentation outlines innovative wave equation migration tools developed as part of a long-term R&D effort. Covering both 2D and 3D methodologies—including paraxial propagators and common-offset wavefield migration—the focus is on achieving true amplitude wavefield migration. The software supports various one-way propagation methods, optimizing accuracy in complex velocity scenarios. Designed for scalability, it employs multifaceted parallelization strategies to handle large datasets efficiently, making it crucial for modern seismic analysis and imaging applications.

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Advanced Wave Equation Migration Techniques for Enhanced Seismic Imaging at SEG 2005

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Presentation Transcript

  1. Presentation of the Wave Equation Migration tool 75th SEG Annual Meeting, Houston, TX. November 6 - 11, 2005.

  2. Long term R&D effort • 2D Paraxial propagator (Collino, 1989) • Constrained least squares migration (Ehinger and Lailly, 1991; Duquet et al., 1994) • Common offset wavefield migration (Ehinger et al.; 1996) • 3D paraxial propagator (Collino and Joly, 1995) • 3D prestack wavefield migration (Duquet et al., 2001) • Comparison of 3D wavefield propagator (Lavaud and Duquet, 2001) • True amplitude wavefield migration (Joncour et al., 2005)

  3. WE Method • Shot record Migration • Accurate • No assumption on the propagation complexity • No assumption on the acquisition geometry • Easy parallelization (shot, frequencies, ...) • Various One-Way propagation kernel • Finite Difference methods, Wavenumber methods, Mixed methods

  4. One-Way propagation methods • Two main approaches : Finite Difference and Wavenumber • Finite difference (paraxial) : • Handle strong lateral velocity variations • Dip limited • Anisotropic Error in 3D (splitting method) • Wanenumber (SSF, PSPI) : • Handle gentle velocity variations • High dip accurate • Isotropic Error • Mixed method (FFD, Li) : • Combine both approaches

  5. Accuracy of FD propagation 2 splitting directions 4 splitting directions 45 ° 68 °

  6. Accuracy vs. Velocity contrasts

  7. Accuracy vs. Velocity contrasts (2)

  8. One-Way propagation method • All these methods are implemented in our software namely: • SSF, PSPI, FD, FFD, LI, Optimized Li • FD propagation kernel: • 2 or 4 splitting directions • Unconditionally stable

  9. Synthetic model Strong velocity contrasts + High dips Layer 1 = homogeneous velocity 1.5 km/s Layer 2 = layer 4 = lateral velocity gradient from 2 to 3 km/s Layer 3 = vertical velocity gradient from 3 to 4 km/s Layer 5 = homogeneous velocity 4 km/s

  10. SSF propagation

  11. FD propagation

  12. FFD propagation

  13. PSPI propagation

  14. Synthetic model

  15. Splitting directions : 2 vs. 4

  16. WE software • 2D/3D shot record migration • Common Angle Gather • Different parallelization level • Optimization strategy • Designed for huge size problem

  17. Master Node Shot parallelization Slave Node n Slave Node 1 Frequency parallelization proc 1 proc 1 proc n proc n Two level parallelization

  18. Two level parallelization • Coarse grain parallelization over shots • Masternode assign and send shared shots to each Slave node • Finer grain parallelization over frequency • Slavenode can be a dual/quadri processor or a cluster subset • mpi parallelization: each processor takes a subset of the frequencies • Reduced communication: • data reading + image condition

  19. Optimization strategy • Shared shot allow to save cost associated with propagation matrix construction • Large step through water • Propagation depth step can be bigger than imaging depth step using an ad'hoc interpolation • ...

  20. dz image=10m / dz propagation=10m

  21. dz image=40m / dz propagation=40m  4 times faster

  22. dz image=10m / dz propagation=40m+ ad'hoc interpolation  3 times faster

  23. dz image=10m / dz propagation=10m

  24. Designed for huge size problem • Memory requirement • Lateral propagation domain : 15km x 10km • Spatial sampling dx=dy=25m • Recording time= 10s • Frequency band = 40Hz (400 frequencies) • ~2 Gb core memory • Flexibility on the frequency range to be migrated

  25. WE software • Shot record migration • accurate method • Fast and flexible algorithm • Various propagation kernels • handle high dips and strong velocity contrasts

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