Carbon Dioxide Storage: Geological Security and Environmental Issues – Case Study on the Sleipner Gas field in Norway (Figure courtesy of Statoil) Semere Solomon Bellona Report May 2007 2 Table of contents Table of contents................................................................................................ 1 Executive Summary, Conclusions and Recommendations.................................. 3 1 Introduction................................................................................................. 7 1.1 Background.............................................................................................................7 1.2 Properties of CO2 and Health Effects......................................................................9 1.3 Sources of CO 2......................................................................................................11 1.4 CO 2 Capture and Storage ......................................................................................11 1.5 Context for CO 2 capture and Storage.....................................................................12 1.6 Potential for reducing CO 2 Emissions....................................................................12 1.7 Layout of the Report .............................................................................................13 2 Geological Framework .............................................................................. 15 2.1 Historical perspectives ..........................................................................................15 2.2 Geological formations...........................................................................................16 2.2.1 General requirements.....................................................................................17 2.2.2 Saline formations...........................................................................................19 2.3 Geological storage ................................................................................................19 2.3.1 Effects of impurities......................................................................................21 2.3.2 Storage in deep saline formations ..................................................................21 2.4 Existing and planned CO 2 projects ........................................................................22 3 Storage mechanisms and storage security.................................................. 27 3.1 CO 2 flow and transport processes..........................................................................27 3.2 CO 2 storage mechanisms in geological formations ................................................30 3.2.1 Physical trapping: stratigraphic and structural................................................30 3.2.2 Physical trapping: hydrodynamic...................................................................30 3.2.3 Geochemical trapping....................................................................................31 3.3 Natural geological accumulations of CO 2 ..............................................................32 3.4 Industrial analogues for CO 2 storage .....................................................................34 3.4.1 Natural gas storage........................................................................................34 3.4.2 Acid gas injection..........................................................................................35 3.4.3 Liquid waste injection ...................................................................................36 3.5 Security and duration of CO 2 storage in geological formations..............................36 4 Site characterization and performance prediction ...................................... 37 4.1 Site characterization..............................................................................................37 4.1.1 Data types .....................................................................................................37 4.1.2 Assessment of stratigraphic factors affecting site integrity.............................38 4.1.3 Geomechanical factors affecting site integrity ...............................................38 4.1.4 Geochemical factors affecting site integrity ...................................................39 4.1.5 Anthropogenic factors affecting storage integrity...........................................39 4.2 Performance prediction and optimization modelling..............................................40 4.3 Remark .................................................................................................................42 5 Monitoring and verification....................................................................... 43 5.1 Purposes for monitoring........................................................................................43 5.2 Monitoring............................................................................................................44 5.2.1 Injection rates and pressures ..........................................................................44 5.2.2 Subsurface distribution of CO 2 ......................................................................44 5.2.3 Injection well integrity...................................................................................46 5.2.4 Local environmental effects...........................................................................46 5.2.5 Network design and duration.........................................................................48 5.3 Verification of CO 2 injection and storage inventory ..............................................49 6 Risk assessment, management, and remediation........................................ 51 6.1 Frameworks for assessing environmental risks......................................................51 6.2 Processes and pathways for release of CO 2 from geological storage sites ..............52 6.3 Risk assessment methodology ...............................................................................54 6.4 Probability of release from geological storage sites ...............................................56 6.4.1 Natural systems.............................................................................................57 6.4.2 Engineered systems.......................................................................................57 6.4.3 Fate of CO 2 in the subsurface ........................................................................58 6.4.4 Numerical simulations of long-term storage performance ..............................58 6.4.5 Assessment of underground CO 2 retention....................................................59 6.5 Possible local and regional environmental hazards ................................................59 6.5.1 Potential hazards to human health and safety.................................................59 6.5.2 Hazards to groundwater from CO 2 leakage and brine displacement ...............60 6.5.3 Hazards to terrestrial and marine ecosystems.................................................61 6.5.4 Induced seismicity.........................................................................................62 6.5.5 Implications of gas impurity ..........................................................................63 6.6 Risk management..................................................................................................64 6.7 Remediation of leaking storage projects ................................................................64 7 Knowledge gaps ........................................................................................ 67 8 Case study - The Sleipner Gas field........................................................... 69 8.1 Background...........................................................................................................69 8.1.1 Offshore geology...........................................................................................69 8.1.2 Utsira Formation ...........................................................................................71 8.1.3 Saline Aquifer Carbon dioxide Storage (SACS) Project.................................73 8.1.4 CO 2 storage quality and capacity ...................................................................74 8.2 Geological Suitability............................................................................................74 8.3 Tasks accomplished ..............................................................................................75 8.3.1 Micoseismic studies ......................................................................................75 8.3.2 Characterisation of the reservoir ....................................................................76 8.3.3 Characterisation of caprocks..........................................................................79 8.3.4 Monitoring the injection process....................................................................81 8.3.5 Integration of time-lapse seismic with reservoir flow model ..........................84 8.3.6 Reservoir simulation in SACS: Verifying the seismic and geological interpretations and predicting the long-term fate of CO 2.................................85 8.3.7 Calibration of a local reservoir model by use of repeated 3D seismic.............85 8.3.8 Simulation of the long-term fate of CO 2 in a large-scale model......................87 8.3.9 Assessing the geochemical effects of CO 2 injection.......................................91 8.3.10 Determination