Oil and Gas Imaging, pumpsandpipesmdhc


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Oil and Gas Imaging, pumpsandpipesmdhc

  1. 1. Oil and Gas Imaging Bruce VerWest, PhD Research Manager – External & Strategic R&D CGGVeritas Pumps & Pipes 1 November 12, 2007
  2. 2. Goal of Seismic Imaging <ul><li>Seismic Imaging – a primary tool for oil & gas exploration </li></ul><ul><ul><li>Determine reservoir geometry, shape, position </li></ul></ul><ul><ul><li>Determine reservoir properties – lithology, pore fill (brine, oil or gas) </li></ul></ul><ul><li>Approach and challanges </li></ul>
  3. 3. Seismic Acquisition – Listening for Echos Marine Acquisition Plan view
  4. 4. Seismic Acquisition – Listening for Echos <ul><li>The Tool </li></ul><ul><ul><li>Acoustic echos (5-80 Hz.) </li></ul></ul><ul><ul><li>Image reflected energy </li></ul></ul><ul><ul><li>Subsurface velocity unknown </li></ul></ul><ul><ul><li>Velocity complex -> ray path distortion </li></ul></ul><ul><li>Limitations of data acquisition </li></ul><ul><ul><li>Data acquired on one side of target – the earth’s surface </li></ul></ul><ul><ul><li>Reservoir details are on order of meters – seismic wavelengths are tens to hundreds of meters </li></ul></ul><ul><ul><li>We are interested in subsurface properties but we measure property contrasts </li></ul></ul>
  5. 5. Seismic Imaging Forward problem Inverse problem Non-unique Incomplete Unstable Acquisition Seismic data Model building Imaging
  6. 6. Seismic Imaging is a Two Step Process <ul><li>Determine velocity -> </li></ul><ul><ul><li>Acquire data with varying source receiver separation </li></ul></ul><ul><ul><li>Use stereo tomography to determine velocity </li></ul></ul><ul><ul><li>Traveltimes yield low resolution view of subsurface velocity </li></ul></ul><ul><li>Image data -> </li></ul><ul><ul><li>Back propagate measured sound wavefield to form image </li></ul></ul><ul><ul><li>Various approximations to the acoustic wave equation are utilized </li></ul></ul><ul><li>Iterative process since the velocity is part of the image </li></ul>
  7. 7. Multiple source receiver separation data <ul><li>Multiplicity of data helps in noise removal </li></ul><ul><li>Traveltimes from data at varying offsets yields information about medium velocity </li></ul>Receiver station Time (sec) Receiver station Source
  8. 8. An Example - Subsurface Model
  9. 9. An Example – Complex Wave Propagation
  10. 10. An Example – Seismic Data x t
  11. 11. An Example – Imaging Velocity x z
  12. 12. An Example – Imaged Output x z
  13. 13. Kirchhoff Beam 1-way Wave Equation Jack Discovery – Different 3D Imaging Algorithms
  14. 14. Changing the acquisition geometry to improve imaging Narrow Azimuth Acquisition Wide Azimuth Acquisition N S N S Jack #1 Jack #1 x X X
  15. 15. Repeat Over 1000’s of sq. km. Detailed depth top salt interpretation covering 19,000 sq km
  16. 16. CGGVeritas Town Park Computer Center Computer Totals Cpu’s >15060 Memory >32 TBytes Disk > 3676 TBytes
  17. 17. Supercomputer Peak Performance 1980 1990 2000 2010 Year Introduced 1 Pflop Peak Speed (flops) 1 Tflop 1 Gflop 1 Mflop CRAY-1 CRAY-2 X-MP4 Y-MP8 SX-4 SX-5 T3D T3E Doubling time = 1.5 yr. Blue Gene (367 Tflops) CGGVeritas Houston
  18. 18. Recent Advances to Improve Imaging <ul><li>More accurate (and expensive) imaging algorithms </li></ul><ul><li>Better tools for velocity model determination </li></ul><ul><li>Increased acquisition aperture </li></ul>
  19. 19. Current Problems in Seismic Imaging <ul><li>Poor illumination – shadows, absorption </li></ul><ul><li>Complex velocity model determination (including anisotropy) </li></ul><ul><li>Imaging steep dips and complex structure </li></ul><ul><li>Resolution –> loss of high frequencies and higher velocity at depth </li></ul><ul><li>Multiple reflections </li></ul><ul><li>Other Noise </li></ul>
  20. 20. Oil and Gas Imaging Pumps & Pipes 1 November 12, 2007