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T.M. Daley, E.L. Majer, L.R. Myer, J.E. Peterson all at Lawrence Berkeley National Laboratory Berkeley, California. Acquisition of time-lapse, 6-component, P- and S-wave, crosswell seismic with orbital vibrator, and of time-lapse VSP for CO2 injection monitoring. Outline.

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Outline

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  1. T.M. Daley, E.L. Majer, L.R. Myer, J.E. Petersonall at Lawrence Berkeley National LaboratoryBerkeley, California Acquisition of time-lapse, 6-component, P- and S-wave, crosswell seismic with orbital vibrator, and of time-lapse VSP for CO2 injection monitoring

  2. Outline • Background of the CO2 Sequestration Pilot • Goals and Design of Time-Lapse Seismic • Crosswell Seismic • Orbital Vibrator Source • Tomography results P and S • VSP • Acquisition Geometry • Time-Lapse Change • Summary/Conclusion Frio Crosswell

  3. Frio Brine Pilot, Dayton, Tx Monitoring Well Injection Well • Injection interval ~7 m at 1530 m depth • ~1600 metric tons CO2 • Well spacing ~30 m • Dip ~20 deg. • Frio ‘C’ Sandstone: porosity 30%, permeability 1.5 Darcys, brine filled • 150 bar, 53 deg. C, supercritical CO2 Oil production Frio Crosswell

  4. Frio Site Frio Crosswell

  5. Goals of CO2 Pilot • Demonstrate that CO2 can be injected into a brine formation without adverse health, safety or environmental effects. • Determine the subsurface distribution of injected CO2 • Demonstrate validity of conceptual models • Develop experience necessary for the success of large scale sequestration efforts Frio Crosswell

  6. Crosswell Spatial mapping of CO2 between wells Measure change in properties of reservoir Combine with other measurements to estimate CO2 saturation between wells. VSP Spatial mapping of CO2 beyond the well pair Imaging of nearby structure (faults, etc) Goals of Seismic Monitoring Frio Crosswell

  7. Data Acquisition • Used orbital vibrator source for P- and S-wave crosswell data; VSP source was seismic explosive • Used P/GSI 80 level 3-component sensor string for both crosswell and VSP • Crosswell 1.5 m spacing, VSP 4 m spacing • Pre Injection Survey: July, 2004 • Post Injection Survey: Nov. 28, 2004 (1.5 months after injection) • Both wells’ perforations were cemented during both surveys Frio Crosswell

  8. Orbital Vibrator Borehole Seismic Source • Fluid Coupled • Rotating eccentric mass • ~70 Hz to 360 Hz • ~8 second sweep • Generates P and S • SH wave decoupled from P-wave -> better S time picks Frio Crosswell

  9. O.V. Operating Principle Top View Schematic DecompositionPrinciple Rotating eccentric mass M From: Daley and Cox, 2001 Frio Crosswell

  10. O.V. Frequency vs Time Max Frequency ~360 Hz Frequency (Hz) 0 100 200 300 400 500 600 700 800 900 1000 0.0 2.0 Time (s) 4.0 6.0 8.0 Frio Crosswell

  11. VSP 3-C Senor in Tubing and Pod Sensor Package Frio Crosswell

  12. Depth (m) Sensor String Deployment Depths 80 levels at ~8m spacing 300 VSP 600 900 1200 Crosswell Fans 1500 Frio Crosswell

  13. Sensor Depth (m) 1375 1675 1375 1675 1500 1500 0 Sensor Hx 150 0 Time (ms) Hy 150 0 Z 150 Source- X Source- Y 6-Component Crosswell Shot Gather P SH P Frio Crosswell

  14. SH-source S-wave Particle Motion AmplitudeHx AmplitudeHy Z Hx Hy Frio Crosswell

  15. P-Wave S-Wave Example Crosswell Time Picks 10 20 30 Time (ms) 40 50 60 70 Frio Crosswell

  16. Pre Injection Post Injection 1475 Depth (m) 1535 1565 0 0 50 50 25 25 Constant 30ft Offset (Along Dip)P-wave Injection Zone Time (ms) Frio Crosswell

  17. Constant 30ft Offset (Along Dip)S-wave Pre Injection Post Injection 1505 Injection Zone Depth (m) 1535 1565 0 0 60 60 30 30 Time (ms) Frio Crosswell

  18. Tomographic Inversion • Limit ray angle (no long offsets, > 100 m) • Correct for deviation of wells • Invert difference; not difference inversions • Use straight ray projection • Apply static correction (borehole effects) • 2 m pixel size • Plotting interpolated to 0.5 m Frio Crosswell

  19. Pre - Post Velocity Difference S-Wave P-Wave Offset (m) 30 30 0 0 1475 1500 Depth (m) Depth (m) 1530 1560 Injection Zone Injection Zone 1600 Frio Crosswell

  20. 30 0 Offset (m) 1505 ‘B’ Sand G.L. Depth (ft) Top of ‘C’ Sand 1530 Depth (m) CO2 Plume 1550 Seismic P-wave and Pulsed Neutron Logs Injection Well Monitor Well Distance (ft) Frio Crosswell

  21. 9 5 N 8 6 1 500 m 4 2 Wells 3 VSP Shot Points Frio Crosswell

  22. Frio Analysis Window Enhanced Reflection Entire VSP Reflection Section Frio Reflection Section Site 1 Depth (m) 1500 1000 500 4 m spacing 0 0 1000 Two-way time (ms) 2000 3000 Frio Crosswell

  23. Processing for Time Lapse Reflection Amplitude Change • Apply static shifts from explosive shot monitor. Edit noisy traces, sort by depth, etc. • Use F-K filters to remove downgoing and enhance upgoing energy. • Obtain reflection section for pre and post data • For time-lapse change: normalize reflection amplitude using a shallower reflector above the frio. • Calculate change in reflection amplitude Frio Crosswell

  24. Site 1 (North, Up Dip) Reflection Section Pre Injection Post Injection Control Reflection Two-way travel time Frio Reflection 1200 1500 1200 1500 Depth (m) 1000 1500 2000 Frio Crosswell

  25. Sensor Depth (m) Frio Reflection Site 1 Reflection Difference (Post – Pre) Major change in Frio due to CO2 injection. Smaller change below Frio probably due to transmission through Frio. 1200 1500 1000 Two-way travel time 1500 2000 Frio Crosswell

  26. Over 70% increase in peak reflection amplitude. This is a strong response. What is cut-off point For plume edge? Pending a rock physics model for Frio. Range of CO2 induced reflection amplitude change. Amplitude Change (Post - Pre)/Pre 30 60 90 120 Site 1 (North): Estimated Plume Size Estimated Reflection Offset (m) Frio Crosswell

  27. Comparison of VSP andModeled Gas Saturation 0 90 150 60 120 30 Offset (m) Frio Crosswell

  28. Conclusions Data Acquisition • Orbital vibrator provides quality P and S crosswell data • 80-level 3-component sensor string good for VSP and crosswell CO2 Detection • Crosswell seismic images the ~800 m/s velocity change due to CO2 plume between wells • VSP easily “sees” the plume as ~70% increase in reflection amplitude –> some surface monitoring is possible without full 3D surface seismic. Frio Crosswell

  29. Acknowledgments • Frio Brine Pilot project supported by U.S. Dept of Energy, National Energy Technology Laboratory • Texas Bureau of Economic Geology managed the Frio Pilot Project • LBNL work supported by U.S. Dept. of Energy, GEO-SEQ Project • Paulsson Geophysical (P/GSI) provided support for use of sensors • Thank you for your attention! Frio Crosswell

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