Fifth Annual Conference on Carbon Capture and Sequestration: May 8-11, 2006

1. 1505 ‘B’ Sand Top of ‘C’ Sand 1530 Depth (m) CO2 Plume 1550 Distance (m) 30 Fifth Annual Conference on Carbon Capture and Sequestration: May 8-11, 2006 Successful Borehole Seismic Imaging of Injected CO2 in a Deep Saline Formation T. M. Daley, L.R. Myer, G.M. Hoversten, S.M. Benson Lawrence Berkeley National Laboratory, Earth Science Division 0

2. Outline • Background of the CO2 Sequestration Pilot • Goals of Crosswell and Vertical Seismic Profile (VSP) • Data Acquisition • VSP Estimate of Plume Extent Compared to Flow Model • Crosswell Tomography and CO2 Saturation Estimate • Integration of Crosswell and VSP using Seismic Modeling • Conclusions • Plans for Frio-II

3. Frio Brine Pilot, Dayton, Tx Monitoring Well Injection Well • Injection interval ~7 m thick 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

4. Frio Site 2004 Work over rig at injection well, crane at monitoring well Recording truck, sensor string on reel, wireline truck

5. Goals of Seismic Monitoring:Scale/Resolution of Geophysical Data VSP

6. Goals of Seismic Monitoring:Time-Lapse Surveys (Pre and Post Injection) • VSP • Spatial mapping of CO2 beyond the well pair • Imaging of nearby structure (faults, etc) • Crosswell • Spatial mapping of CO2 between wells • Combine with other measurements to estimate CO2 saturation between wells.

7. Data Acquisition • Orbital vibrator source for crosswell; explosive source for VSP • P/GSI 80 level 3-component sensor string for 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

8. 9 5 300 N VSP 600 8 6 1 Depth (m) 900 500 m 4 2 Wells 1200 3 Crosswell Fans 1500 VSP: 8 Source Points 80 Sensor levels at ~8m spacing Source Points – Plan View Sensor Depths

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

10. Pre Injection Post Injection Control Reflection Two-way travel time Frio Reflection VSP Time-Lapse Reflection Amplitude Change Site 1 1200 1500 1200 1500 Depth (m) 1000 1500 2000

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

12. Over 70% increase in peak reflection amplitude. This is a strong response. Amplitude change is a function of CO2 Saturation. Result: VSP can be used to Estimate the extent of CO2 plume. Amplitude Change (Post - Pre)/Pre 30 60 90 120 Site 1 (North): Estimated Plume Extent Estimated Reflection Offset (m)

13. Comparison of VSP and Modeled CO2 Saturation 0 90 150 60 120 30 Offset (m)

14. Comparison of 3 Azimuths Flow modeling: C. Doughty

15. Pre Injection Post Injection 1475 Depth (m) 1535 1565 0 0 50 50 25 25 Crosswell : Raw seismograms show change Injection Zone Time (ms)

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

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

18. Injection Well Distance (m) Monitor Well 30 0 1505 ‘B’ Sand Top of ‘C’ Sand 1530 Depth (m) 1550 CO2 Plume Seismic P-wave and Pulsed Neutron (RST) Logs

19. 0 % CO2 10 20 CO2 Saturation From Seismic using a rock physics model Crosswell Derived CO2 Saturation 0 15 30 Result: Crosswell seismic can be used to estimate CO2 saturation spatially between wells.

20. Does the crosswell measurement explain the VSP result? VSP Velocity Model Modeled Data Source Injection Zone Pre Post Finite-Difference seismic modeling of VSP using Crosswell measured velocity shows changes observed in field.

21. VSP Amplitude (Post - Pre)/Pre Comparison of Model and Field VSP Data Model with constant change for predicted plume extent > 130 m Field Data Model with variable change, only between wells ~ 30 m Result: Crosswell can predict VSP change if we know how to estimate CO2 saturation beyond boreholes..

22. Conclusions • Crosswell seismic images ~500 m/s (20%) velocity change due to CO2 plume between wells.  Estimate CO2 saturation with rock physics model • VSP easily “sees” the plume as ~70% increase in reflection amplitude.  Some surface monitoring is possible without full 3D surface seismic. • VSP can estimate the extent of CO2 plume on different azimuths. • Results of crosswell and VSP can be integrated with flow model to improve predictions of storage performance.

23. Concluding Comment and Plans for Frio-II Permanent installation of seismic sensors could be a cost effective tool for characterization and long term monitoring of sequestered CO2. Frio – II Plans: Semi-permanent, tubing-deployed crosswell monitoring during injection. One source, 24 Sensors Injection Interval: ‘Blue’ sand ~1650 m

24. Acknowledgements • Frio Brine Pilot project supported by U.S. Dept of Energy, National Energy Technology Laboratory • Texas Bureau of Economic Geology (S. Hovorka) 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 • Flow modeling by Chris Doughty (LBNL) • Thank you for your attention!