CO 2 Geological Storage Principles, Applicability in Canada, and Challenges

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1 CO 2 Geological Storage Principles, Applicability in Canada, and Challenges Dr. Stefan Bachu Principal Scientist, CO 2 Storage Stefan.Bachu@albertainnovates.ca Associate Editor (Storage) Outline Relevant CO 2 properties, CO 2 trapping mechanisms, and means and media for CO 2 storage Identifying storage options and appropriate injection sites Estimation of CO 2 storage capacity Applicability to Canada and challenges to deployment Relevant CO 2 Properties, CO 2 Trapping Mechanisms, Means and Media for CO 2 Geological Storage Phase Diagram for Carbon Dioxide CO 2 Density for Pressure and Temperature Conditions in the Earth Crust Variation with Depth and Geothermal Regime of Carbon Dioxide Density

2 Trapping of CO 2 in the Pore Space at Irreducible Saturation In pure water Carbon Dioxide Solubility in Water In brine Sequence of Geochemical Reactions between CO 2 and Formation Water and Rocks Aqueous Species Dominance Diagram 1. Solubility Trapping CO 2(g) CO 2(aq) CO 2(aq) + H 2 O H 2 CO 3(aq) 2. Ionic Trapping H 2 CO 3(aq) HCO 3(aq) + H + HCO 3(aq) CO 2-3(aq) + H + 3. Mineral Trapping CO 2-3(aq) + Ca 2+ CaCO 3(s) HCO 3(aq) + Ca 2+ CaCO 3(s) + H + Adsorption of Various Gases on Coal Trapping Mechanisms for CO 2 Physical Trapping (in free phase) In large, man-made caverns In the pore space Mobile in structural and stratigraphic traps (static trapping) in regional-scale flow systems (hydrodynamic trapping) Immobile: at irreducible saturation Chemical Trapping (in a different phase) In solution in formation fluids (oil or water) Adsorbed onto organic material in coals and shales As a mineral precipitate

3 Geological Media Suitable for CO2 Storage Porous and permeable rocks (sandstone and carbonate) overlain by tight rocks (shales and evaporitic beds): ¾ Oil and gas reservoirs ¾ Deep saline aquifers Coal beds and organic shales Means for CO2 Geological Storage As a byproduct in energy production operations In oil reservoirs in enhanced hydrocarbon recovery In coal beds in enhanced coalbed methane recovery In disposal operations In depleted oil and gas reservoirs Salt caverns All are geological media found ONLY in sedimentary basins Basalts are also considered based on rapid chemical reactions Means of CO2 Geological Storage Temporal Scales of CO2 Injection and Geological Storage Processes In deep saline aquifers In salt caverns (mainly as a buffer in CO2 collection and distribution systems) Relation between Pressure Behavior, Risk, Monitoring and Legal-Regulatory Aspects in CO2 Geological Sequestration Relation between Time, Trapping Mechanisms and CO2 Storage Security From IPCC SRCCS, 2005

4 Trends Regarding Storage Media Five years after the IPCC Special Report on CCS: Ocean storage is dead Challenges in geological storage: Storage in salt caverns is neglected (minor potential, only as a buffer in delivery systems) Storage in coal beds (ECBM) is still largely unproven and many challenges still need to be overcome, particularly loss of permeability (injectivity) as a result of coal swelling in the presence of CO 2 (is this option slowly dying? ) Storage in organic-rich shales is in the research stage, presents the same challenges as storage in coal beds, and as shale gas production advances (fracturing to increase permeability) it destroys the integrity of the storage unit Storage in basalts has yet to be demonstrated, it is based on the concept of rapid geochemical reactions, otherwise basalts are poor containers Storage in shallow seabed sediments is researched because of special conditions of high pressure and low temperature, conducive to CO 2 hydrate formation Trends Regarding Storage Media Potential winners in geological storage: Storage in oil fields, contemplated in conjunction with CO 2 -EOR ($$$$, however, they have relatively small capacity) Storage in depleted gas fields is an option rarely pursued, although capacity is significant (EGR is impractical) The focus is on demonstrating CO 2 storage in deep saline aquifers which are widespread and have the largest storage capacity! However, all these three options suffer from the lack of CO 2 supply (capture) and infrastructure (transportation) to bring the CO 2 from source to sink Summary CO 2 can be trapped in geological media in free phase, in solution, adsorbed onto coal and shales, and as a mineral precipitate The most promising storage media are oil and gas reservoirs and deep saline aquifers Various trapping mechanisms operate on different spatial and temporal scales that need to be taken into account From a safety and security point of view, the most important period is the active injection period, although some risk may occur later on as the plume of CO 2 migrates and may encounter a leakage pathway Identifying Storage Options and Appropriate Injection Sites Operational Stages of CO 2 Storage Basic Principles 1 Site characterization is a continuous, iterative process during all operational stages of a CO 2 storage project Monitoring is a key element in site operation, closure and postclosure, likely to be a permitting requirement Storage safety and security is a common thread throughout all the stages of the operational chain and has to be demonstrated when applying for tenure of the storage unit and permit to operate, during operations, and after cessation of injection to complete site abandonment

5 Required Characteristics of Geological Media Suitable for Storage of Fluids Capacity, to store the intended CO 2 volume Injectivity, to receive the CO 2 at the supply rate In real time, i.e., during the active-injection phase, based on primary trapping mechanisms. However, if capacity and/or injectivity are insufficient, some measures can be taken (e.g., use multiple and/or horizontal wells, use several storage sites, store less CO 2 ). Containment, to avoid or minimize CO 2 leakage During all phases of a CCS operation. If containment is defective, then the prospective site is disqualified! Screening and Selection of Sites for CO 2 Storage At the basin scale At the local scale Eliminatory Criteria for Sedimentary Basins Criterion Depth Aquifer-seal pairs Pressure regime Seismicity Faulting and fracturing Hydrogeology Areal size Legal accessibility Unsuitable < 1000 m Poor (few, discontinuous) Overpressured High and very high Extensive Shallow, short flow systems <2500 km 2 Forbidden Suitable >1000 m Intermediate, excellent Hydrostatic Very low to moderate Limited to moderate Intermediate, regional-scale flow systems >2500 km 2 Allowed Cross Sectional Representation of Sedimentary Basins across Canada Seismicity in Canada Desirable Characteristics of Sedimentary Basins Criterion Within fold belts Significant diagenesis Geothermal regime Evaporites Hydrocarbon potential Industry maturity Coal seams Coal rank Coal value On/offshore Climate Accessibility Infrastructure CO 2 sources <500 km Undesirable Yes Present Warm basin Absent Absent/small Immature Absent, shallow or very deep Lign./Anthracite Economic Deep offshore Harsh No or difficult Absent/undev. Absent Desirable No Absent Cold basin Present Medium/giant Mature Between 400 m and 800 m depth (sub) Bituminous Uneconomic Onshore, shallow Moderate Good Developed Present

6 Site-Scale Scale Selection Sites must pass the basin-scale eliminatory criteria, and should broadly possess basin-scale desirable characteristics In addition, sites must pass and/or meet additional criteria that fall broadly into five categories: Capacity and injectivity Confinement, i.e., safety, security and environmental acceptability Legal and regulatory restrictions Economic Societal (public acceptance) The same criteria can be organized into: Eliminatory criteria: sites are eliminated if they don t meet these criteria Selection criteria: sites are selected if they meet most or the preferred of these criteria, depending on local circumstances Eliminatory Site Selection Criteria Legally inaccessible (in protected areas) 2. Legally unreachable (right of access cannot be secured) 3. Legally unavailable (e.g., equity interest held by third parties) 4. Physically unavailable (e.g., a hydrocarbon reservoir in production, an aquifer used for geothermal energy or for natural gas storage) 5. Located in high-density population areas flexible 6. Potentially affecting other natural, energy and mineral resources and equity Eliminatory Site Selection Criteria Within the depth of protected groundwater 8. In hydraulic communication or contact with protected groundwater 9. Located at shallow depth (< m) debatable in some cases! 10. Lacking at least one major, extensive, competent barrier to upward CO 2 migration 11. Located in an area of very high seismicity 12. Located in over-pressured strata 13. Lacking monitoring potential Site Selection Criteria - 1 For efficacy of storage: 1. Sufficient capacity and injectivity: they are not independent, injectivity may limit real-time capacity! 2. Sufficient thickness 3. Low temperature 4. Favorable pressure and hydrodynamic regime Site Selection Criteria - 2 For safety and security of storage: 5. Low number of penetrating wells 6. Presence of multi-layered overlying system of aquifers and aquitards (secondary barriers to upward CO 2 migration) 7. Potential for attenuation of leaked CO 2 near and at surface For cost: Site Selection Criteria Accessibility and infrastructure (location, terrain, climate, right of access, avoidance of populated/protected areas) 9. Transportation economics (distance from source, pipelines of shipping facilities, compression and site delivery) 10. Storage economics (site facilities, wells and compression, operational and environmental monitoring)

7 Additional Site Selection Criteria? Depth Thickness Porosity Permeability Water salinity Estimation of CO 2 Storage Capacity These have been suggested in the past, but they are implicit in (proxies for) the criteria of capacity, injectivity, and protection of groundwater and/or mineral resources They still can be used as selection criteria, but they are not completely independent and changes in one may affect another Assessment Types Techno-Economic Resource-Reserves Reserves Pyramid for CO 2 Storage Capacity Theoretical: physical limit of the system Effective: accounts for geological and engineering cut-offs Practical: accounts for technical, legal and regulatory, infrastructure and economic barriers Matched: obtained by source-sink matching (SSM) CO 2 Storage Capacity in Depleted Oil Reservoirs Theoretical Capacity or M CO2t = ρ CO2r [ R f OOIP / B f -V iw + V pw ] M CO2t = ρ CO2r [R f A h φ (1 S w ) V iw + V pw ] M CO2t : Theoretical storage capacity ρ CO2r : CO 2 density at initial reservoir conditions R f : Recovery factor OOIP: Original Oil in Place B f: Formation factor A: Reservoir area h: Reservoir thickness φ: Porosity S w : Water saturation V iw : Volume of injected water V pw : Volume of produced water CO 2 Storage Capacity in Depleted Gas Reservoirs Theoretical Capacity M PS Z r Tr = R f (1 FIG ) OGIP P Z T CO2t ρco2r M CO2t : Theoretical storage capacity ρ CO2r : CO 2 density at initial reservoir conditions R f : Recovery factor OGIP: Original Gas in Place F IG : Fraction of (re-)injected gas r P: Pressure T: Temperature ( K) Z: Z-factor (gas compressibility) r,s: reservoir; surface subscripts S S

8 CO 2 Storage Capacity in Depleted Oil and Gas Reservoirs Effective Capacity M CO2e = C m C b C h C w C a M CO2t C e M CO2t CO 2 Storage Capacity in Structural and Stratigraphic Traps in Deep Saline Aquifers Theoretical Capacity V CO2t = V trap φ (1 S wirr ) A h φ (1 S wirr ) or, if the spatial variability is known M CO2t : Theoretical storage capacity M CO2e : Effective storage capacity C: Reduction coefficients Subscripts m: mobility b: buoyancy h: heterogeneity w: water saturation a: aquifer strength t: theoretical e: effective VCO 2t = φ (1 S wirr ) dxdydz Effective Capacity V CO2e = C c V CO2t V CO2t : Theoretical storage volume V CO2e : Effective storage volume V trap: Trap volume φ: Porosity S w : Irreducible water saturation A: Average trap area h: Average trap height C c : Capacity coefficient CO 2 Storage Capacity in Residual-Gas Traps in Deep Saline Aquifers V CO2t = ΔV trap φ S CO2t V CO2t : Theoretical storage volume ΔV trap : Volume invaded by water previously occupied by the plume of injected CO 2 φ: Porosity S CO2t : Saturation of trapped CO 2 It is a time-dependent process, as the CO 2 plume migrates Storage capacity can be determined by numerical simulations only, based on real relative-permeability data CO 2 Storage Capacity in Solution in Deep Saline Aquifers Theoretical Capacity M = A h φ ( ρsx CO 2t or, if the spatial variability is known Effective Capacity CO S CO 2 CO 2 M CO 2t = ( SX S 0 φ ρ ρ X 0 ) dxdydz M CO2e = C c M CO2t M CO2t : Theoretical storage capacity A: Aquifer area h: Aquifer thickness φ: Porosity ρ: Water density X CO2 : Carbon content in formation water C c : Capacity coefficient s,0: saturation and initial, subscripts 2 ρ 0 X CO 2 0 ) Applicability of Methodologies for Estimating CO 2 Storage Capacity to Various Assessment Scales Applicability to Canada And Challenges to Deployment

9 Canada s 2000 Carbon Dioxide Emissions (Mt/year) Distribution of Large Stationary CO 2 Sources and Sedimentary Basins in Canada Worldwide Experience with Geological Sequestration of CO 2 We know how to do it! >100 Enhanced oil recovery operations (102 in the U.S., 3 in Canada), since the 70 s >60 Acid gas disposal operations (44 in Canada, >16 in the U.S.), since CO 2 disposal operations into an aquifer (Sleipner, Mongstad and In Salah), since enhanced coalbed methane recovery (San Juan basin, U.S.A.) CO 2 Pipeline Network in the U.S. Current Acid Gas and CO 2 Injection Operations in Canada Annual CO 2 transport: ~50 Mt/year on >5600 km pipeline

10 Barriers to Deployment Then why is it not deployed?? Scientific and technological Scale and system integration Economic and financial Legal and regulatory Public attitude and acceptance Capacity High cost of CO 2 capture Lack of infrastructure Economic Issues Current lack of market incentives or regulatory penalties Energy consumption in the process of CO 2 sequestration Lack of knowledge about available and potential storage capacity by type and geographically Matching large CO 2 sources and sinks and network optimization Legal Issues Ownership of the pore space and resources within national boundaries and in international waters Ownership of the stored CO 2 and third party transfer Relationship between ownership of the pore space and other property rights Long term liability, particularly after cessation of CO 2 injection Trans-boundary CO 2 sequestration and/or migration Access rights Regulatory Issues No clear & fully encompassing regulatory regime for the capture, transportation and injection stages of CO 2 geological storage, although current regulations for capture, transportation and injection are, by and large, adequate Regulations for the injection stage can be modeled (adapted or adopted) after those in North America that deal with oil and gas conservation and/or with acid gas and waste disposal Liability along the CCS Chain Liability during CO 2 capture, transportation and injection is well covered by existing legislation and practices Post-operational liability needs to be established No regulatory regime for the post-injection stage of CO 2 geological storage

11 Public Acceptance The public is not convinced that geological sequestration is both needed and safe Many environmental Non-Governmental Organizations view CO 2 geological sequestration as a means to avoid reductions in fossil fuel use Not under my back yard NUMBY syndrome The public is wrongly informed and/or asked the wrong question Capacity CO 2 capture and storage needs engineers for capture and transportation; geologists, hydrogeologists and geochemists for site selection and characterization, reservoir engineers, economists,., i.e., a skilled work force that does not exist today and that has to be trained formally and in the field Current CCS Projects in Western Canada Conclusion CO 2 Capture and Geological Storage will play an important role in the reduction of anthropogenic emissions of CO 2 in Canada and will be an integral part of future energy systems Contact Dr. Stefan Bachu stefan.bachu@albertainnovates.ca