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Monitoring Protocols

Monitoring Protocols. G. Michael Hoversten Sally Benson Erika Gasperikova Lawrence Berkeley National Laboratory. Introduction. Sequestration examples Sleipner Numerical simulation Project phases and monitoring Key Monitoring elements Remote sensing Surface measurements Geophysics

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Monitoring Protocols

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  1. Monitoring Protocols G. Michael Hoversten Sally Benson Erika Gasperikova Lawrence Berkeley National Laboratory

  2. Introduction • Sequestration examples • Sleipner • Numerical simulation • Project phases and monitoring • Key Monitoring elements • Remote sensing • Surface measurements • Geophysics • Monitoring Purpose & methods • Conclusions

  3. Sleipner (North Sea) • Critical Factors • Pressure gradient • Permeability • Residual gas saturation • Density contrast • CO2 moves vertically by buoyancy forces • 100m in 5 years at Sleipner (probably within 1 year) • Below ~ 800 m CO2 is liquid state • Density ~ 20% less than brine • Above ~ 800 m CO2 is in gas state • Density ~ 99% less than brine

  4. Numerical Simulation • Residual gas saturation is a factor controlling transport • This expresses how much CO2 stays behind in the pore space as fluid movement occurs • CO2 Dissolves into brine • On 1000s year time scale CO2 rich water sinks due to increased density

  5. Project Phases & Monitoring • Pre-operation • Characterization of the reservoir • All background levels of CO2 • Air, water, soil • Operations • Most vigorous monitoring • Reservoir & seal performance • Closure • Surface facilities removed, wells plugged • Confirmatory period to demonstrate that the storage project is performing as expected • Post Closure • Monitoring ends except for • On-going low level leakage • If new information is needed or legal disputes

  6. Project Phases & Monitoring

  7. Key Monitoring elements • Airborne monitoring • LIDAR (light detection and range-finding) a scanning airborne laser, and DIAL (differential absorption LIDAR) • Hyper-spectral imaging • Specific habitats can be identified by their spectral signature • CO2 stress on vegetation shows up as changes in plants reflectivity at certain wavelengths • Surface Detection & Quantification • Infrared gas analyzers (IRGA) • Well heads • Basements & depressions • Soil sampling • Geochemical Monitoring • Impact to ground water (analyzed for major ions) • Chemical tracers (interaction with the reservoir) Image after Pickles 2003

  8. Key Monitoring elements • Well head injection rate & pressure • Over pressuring the reservoir can lead to hydraulic fracturing • Loss of seal integrity • Well failure • Geophysical Detection • Mapping spatial changes as injection proceeds • Anomalous event indicator • Leaks • Unforeseen transport paths within formation • Geophysical Quantification • How much CO2 is present at a given location • Process control to optimize SCO2 • How accurate are flow model predictions? • Dependent on many more assumptions and knowledge than detection for success

  9. Key Monitoring elements • Leaks • Seismic is the best way to see leaking CO2 EARLY • Large velocity change with small % CO2 above ~ 1200m • Very thin (5m) accumulations will show up on a seismic section • Assumption: the CO2 will move out laterally at some point on its upward migration • Vertical CO2 zones are much harder to see

  10. Monitoring Purpose & Methods

  11. Later project Protocols • Well head sensors • Airborne imagery • Periodic water well sampling • Subsurface Detection only • Seismic at 1 year • Micro-seismicity for 1 or 2 years • Continuation depends on activity • Seismic every 5 years for leak detection • Gravity & possible EM every few years • Lower cost & resolution • Surface Deformation • Permanent Scatter Technique (enhanced In-SAR) • $100 / raw data • mm resolution

  12. Conclusions • Early projects will be test beds • Monitoring Protocols will have to be site specific • Site characterization is critical for proper design • Research is ongoing into sensitivity levels and improvements of all monitoring systems • Subsurface geophysics will dominate costs • Seismic is highest cost, highest resolution, best early warning of leak in time to prevent CO2 reaching the surface • Subsurface monitoring with petroleum heritage is the most developed

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