1. Copyright 2003 SIEP B.V. Shell Exploration & Production Risk Assessment for Geological CO 2 Storage Wolf Heidug

2. Copyright 2003 SIEP B.V. Why is RA for sequestration so important? Relevance for public policy and public acceptance - Precautionary Principle - Safe Minimum Standard Large scale – several hundreds of times the amount injected for CO 2 -EOR Long storage times – several hundreds of years or even longer

3. Copyright 2003 SIEP B.V. The basic questions 1. What can go wrong? 2. How likely is it to occur? 3. What are the effects? 4. What is the net risk?

4. Copyright 2003 SIEP B.V. What the literature says Sally Benson et al., Geological Storage of CO2: Lesson learned. Report, Lawrence Berkeley National Laboratory Download at: www. co2captureproject.org/reports

5. Copyright 2003 SIEP B.V. Analogues for Geologic Storage of CO 2 Industrial Analogues Deep injection of liquid and hazardous wastes Natural gas storage CO 2 enhanced oil recovery Occupational health and safety regulations Nuclear waste storage* Natural Analogues Oil and gas reservoirs Natural CO 2 reservoirs Natural CO 2 releases Volcanic eruptions Hydrothermal vents Limnic releases Diffuse venting Ecosystem CO 2 cycling * Limited relevance but some important lessons

6. Copyright 2003 SIEP B.V. Lesson 1 The health effects of exposure to elevated concentrations of CO 2 are well understood and occupational safety regulations are in place for safe use Confined space hazards Transportation Food additive Pipeline transportation

7. Copyright 2003 SIEP B.V. Humans tolerate up to 1% with no adverse effects Significant effect on respiratory rate and physical discomfort at 3-5% Death imminent at >30% for several minutes Health Effects and Impact on Flora Concentrations near 5% retard vegetation Phytotoxic at 20%

8. Copyright 2003 SIEP B.V. Lesson 2 The hazard depends more on the nature of the release than the size of the release Volcanic eruptions Ecosystem fluxes Confined space releases (fire suppression) Limnic releases Releases that are quickly dispersed in the atmosphere appear to provide little hazard

9. Copyright 2003 SIEP B.V. Concentrated Releases in Confined Spaces are the Most Hazardous Source: S. Benson. Lawrence Livermore National Laboratory

10. Copyright 2003 SIEP B.V. Lesson 3 Experience from industrial analogues suggests that the biggest risks from CO 2 storage will be due to: Leakage through poor quality or aging injection well completions Leakage up abandoned wells Leakage due to inadequate caprock characterization

11. Copyright 2003 SIEP B.V. Categories event-driven variants process-driven variants Deterministic (classical) risk assessment Probabilistic risk assessment Qualitative studies

12. Copyright 2003 SIEP B.V. Event vs. Process-driven RA Event-driven RA event frequencies event tree analysis and fault tree analysis operational systems Process-driven RA system properties affected ongoing processes natural systems scenario analysis

13. Copyright 2003 SIEP B.V. FEPs and all that F eature: characteristic of system components boreholes, lithography, nearby communities,... E vent:a particular happening pipe fracture, nearby earthquake, meteorite impact... P rocess: natural phenomenon corrosion of casing, dissolution of packing material, convection of groundwater... Scenario

14. Copyright 2003 SIEP B.V. A scenario

15. Copyright 2003 SIEP B.V. FEP identification Classification Ranking Screening and Interaction Grouping and Selection Scenarios Scenario Development

16. Copyright 2003 SIEP B.V. Entry in FEP Database Try it out at: http://www.quintessa-online.com/co2

17. Copyright 2003 SIEP B.V. FEP Interaction Matrix Influence diagrams Tools for Scenario Building

18. Copyright 2003 SIEP B.V. Modelling Scenarios form basis for computer modelling Numerical simulator used in petroleum and geothermal industry and for groundwater management are starting points Limited capabilities for comprehensive treatment of coupled process, in particular reactive multiphase flow and geomechanics

19. Copyright 2003 SIEP B.V. Status Several substantial efforts underway Weyburn, NGCAS, SAMSCARD, RITE, CO2CRC, UK-DTI, CO2SINK Cooperation on development of integrated FEP database Aligning methodolgies Improving modelling capabilities

20. Copyright 2003 SIEP B.V. Issues Expert opinion versus transparency? Public acceptance versus complexity of RA?