2007 RESEARCH ACCOMPLISHMENTS AND 2008 GOALS FOR UTAM

  1. Seismic Interferometry
    • RESULTS:
      • The book "Seismic Interferometry" is completed and sent to Cambridge Press for publication. Sponsors get one xeroxed copy of the book but cannot duplicate it unless they pay a fee of $50. to Cambridge Press. MATLAB (and some Fortran code) codes are included. Good semi-comprehensive tutorial for seismic interferometry.
      • A new interferometric method is devised to extrapolate marine SSP and OBS receivers to be far outside the recording array. Results suggest some of the following possibilities: wide-angle data can be collected from narrow recording arrays, the recording aperture can be more than doubled in conventional OBS surveys, and we can overcome problems in shooting seismic in towns where vibrators are forbidden.
      • Tested interferometric interpolation of deviated VSP and 2D SSP data. Results suggest a noticeable improvement if a matching filter is also used. The matching filter noticeably improves the quality of the virtual traces. Field data tests validate the effectiveness of this method.
      • Filtering surface waves by surface wave interferometry improved by wavelet deconvolution. We need a good 3D land data set to test this method.
      • Source wavelet extraction by interferometry. Preliminary results are encouraging for extracting the source wavelet from seismic data.
      • Least squares redatuming show excellent noise reduction.
    • IMPLICATIONS: Sponsors are 1st recipients of Seismic Interferometry book. It contains many new ideas not yet published. MATLAB codes can be used to improve a reader's understanding and also test ideas. Interferometric extrapolation opens up the door to increasing aperture of short receiver arrays. Perhaps redesign of OBS surveys is in order.
    • PROBLEMS: We need 3D land and marine data to test our algorithms.
    • 2008 GOALS: Further tests for interferometric extrapolation, interpolation, wavelet extraction, and surface-wave filtering of seismic data. Further development of matching filter.

  2. Migration
    • RESULTS:
      • 2D and 3D least squares migration (LSM) of synthetic and field data. Noticeable improvement in the 2D data results. The 3D data requires much computation time so we only show preliminary results.
      • 2D deconvolution imaging condition for migration successfully tested.
      • 3D tests of Bottom-Up reverse time migration (BUM) on synthetic data show noticeable improvement of subsalt imaging compared to Kirchhoff migration. The other advantage is BUM should be several orders of magnitude faster than full volume reverse time migration (RTM). Test on 2D marine data are successful.
    • IMPLICATION: The LSM migration images are better resolved at intermediate and shallow depths, especially for fault identification. Should we reprocess old migration images to get noticeably better resolution. The 2D deconvolution images show much better resolution and illumination compared to standard migration images. BUM can be practically applied to 3D field data. Should we use these last two methods more often?
    • PROBLEMS: More time is needed to test the 3D LSM algorithm; 30 or more iterations are needed for acceptable convergence. We need a 3D salt data set to test our BUM algorithm. The 2D deconvolution methods needs up and downgoing wave separation.
    • 2008 GOALS: LSM in less than 10 iterations. Design 2D deconvolution for data that cannot be decomposed into up and down fields. Apply BUM to 3D data if sponsors give us a 3D salt data set.

  3. Tomography
    • RESULT:
      • Test of multi-scale tomography shows significant improvement in inverting synthetic data compared to EWT or traveltime tomography. Results on field data are encouraging.
    • IMPLICATION: Multi-scale tomography appears to be the right way to go in x-t waveform inversion.
    • PROBLEMS: Slow progress due to limited computer resources.
    • 2008 GOALS: Full multi-scale tomography on marine data. Possibly start work on elastic tomography.

  4. Imaging Passive Seismic Data
    • RESULTS:
      • Used Time Reversal Mirror method for estimating locations of hydro-frac sources and lost miner. Synthetic and field data tests demonstrate that the sqrt(N) signal-to-noise enhancement (where N is the fold number in a stacked trace) and Rayleigh resolution laws can be broken by TRM.
      • Extraction of Green's function from 17 minutes of 3D passive data encouraging.
    • IMPLICATION: New understanding about capabilities of reverse time migration. Good start for processing 3D passive seismic data. Practical method for finding location of trapped miners; robust method for hydro-frac source location.
    • PROBLEMS: Lack of passive seismic data, only 17 minutes was given to us.
    • 2008 GOALS: Full tests on extensive Aramco passive seismic data recently given to us. Collect 3D mine data and 3D array tests with TRM.

  5. Summary of Goals
    • We hope to apply bottom-up RTM on a 3D field data set. More tests by applying interferometric interpolation, extrapolation, and 2D deconvolution methods to OBS and SSP field data. Attention will be devoted to designing a better matching filter. There will be a major effort devoted to multiscale tomography. Chaiwoot will devote full time to this endeavor and one other student will likely be involved. Natural datuming methods will use VSP data to extrapolate SSP data below the overburden and salt. Surface wave filtering will be tested on 3D field data. Least squares migration in less than 10 iterations. Process days of Aramco 3D passive seismic data. Estimation of hydro-frac source location and reflectivity distribution from passive seismic data. Conduct 3D passive seismic experiment in another mine and further develop TRM method.