While the purpose of geologic storage of CO{sub 2} in deep saline formations is to trap greenhouse gases underground, the potential exists for CO{sub 2} to escape from the target reservoir, migrate upward along permeable pathways, and discharge at the land surface. Such discharge is not necessarily a serious concern, as CO{sub 2} is a naturally abundant and relatively benign gas in low concentrations. However, there is a potential risk to health, safety and environment (HSE) in the event that large localized fluxes of CO{sub 2} were to occur at the land surface, especially where CO{sub 2} could accumulate. In this paper, we develop possible scenarios for large CO{sub 2} fluxes based on the analysis of natural analogues, where large releases of gas have been observed. We are particularly interested in scenarios which could generate sudden, possibly self-enhancing, or even eruptive release events. The probability for such events may be low, but the circumstances under which they might occur and potential consequences need to be evaluated in order to design appropriate site selection and risk management strategies. Numerical modeling of hypothetical test cases is needed to determine critical conditions for such events, to evaluate whether such conditions may be possible at designated storage sites, and, if applicable, to evaluate the potential HSE impacts of such events and design appropriate mitigation strategies

Birkholzer, Jens

Karimjee, Anhar

Lewicki, Jennifer

Pruess, Karsten

Tsang,Chin-Fu

UNT Digital Library

Abstract GHGT-8  1 Evaluating Potential for Large Releases from CO2 Storage Reservoirs:  Analogues, Scenarios, and Modeling Needs Jens Birkholzer*1, Karsten Pruess1, Jennifer Lewicki1,  Chin-Fu Tsang1, Anhar Karimjee2 1Lawrence Berkeley National Laboratory,  Berkeley, CA, USA  2U.S. Environmental Protection Agency,  Washington D.C., USA Introduction While the purpose of geologic storage of CO2 in deep saline formations is to trap greenhouse gases underground, the potential exists for CO2 to escape from the target reservoir, migrate upward along permeable pathways, and discharge at the land surface. Such discharge is not necessarily a serious concern, as CO2 is a naturally abundant and relatively benign gas in low concentrations. However, there is a potential risk to health, safety and environment (HSE) in the event that large localized fluxes of CO2 were to occur at the land surface, especially where CO2 could accumulate. In this paper, we develop possible scenarios for large CO2 fluxes based on the analysis of natural analogues, where large releases of gas have been observed. We are particularly interested in scenarios which could generate sudden, possibly self-enhancing, or even eruptive release events. The probability for such events may be low, but the circumstances under which they might occur and potential consequences need to be evaluated in order to design appropriate site selection and risk management strategies. Numerical modeling of hypothetical test cases is needed to determine critical conditions for such events, to evaluate whether such conditions may be possible at designated storage sites, and, if applicable, to evaluate the potential HSE impacts of such events and design appropriate mitigation strategies. Methodology and Results Various natural analogues with large releases of CO2 have been evaluated, placing emphasis on the geologic model for CO2 accumulation, processes leading to the releases of CO2, pathways for migration, and type of release at the surface. Table 1 gives a summary of these analogues and their characteristics. While detailed information on geologic models of accumulation or on migration pathways is often unavailable, a few general conclusions can be drawn with respect to release scenarios and modeling studies important for the risk assessment of geologic storage of CO2.  1. Large releases often originate from natural CO2 plumes that have risen from depth and accumulated under low-permeability caprock. This suggests that the possibility of large CO2 discharges at the land surface is not necessarily linked to fast release from the primary storage formation. In fact, the length of the flow pathway from depth and various mitigating effects make such a scenario rather unlikely. Conditions more conducive to a large, sudden release would involve accumulation of slowly leaking CO2 in a secondary formation closer to the land surface. Suitable conditions could be provided by an anticlinal                                                  * Corresponding Author: jtbirkholzer@lbl.gov, +1 510 486 7134 Abstract GHGT-8  2 structure with a good caprock, where CO2 can accumulate until it reaches a spillpoint. It is thus important to consider the potential for secondary storage reservoirs in a site evaluation and, if applicable, to determine the accumulation and possible release of CO2 from such secondary reservoirs in numerical modeling studies. 2. Faults and fracture zones are the main pathways for gas migration in most natural analogues with large CO2 discharge. It is thus mandatory to be able to predict qualitatively and quantitatively the fast upward flow of CO2 in high-permeability zones that may extend from depth to surface. It is possible that such pathways are generated during or after injection by disruptive events related to geomechanical failures or seismic activity. During upward migration, CO2 is affected by transitions from super- to sub-critical conditions, by phase changes between liquid and gaseous CO2, phase partitioning between water-rich and CO2-rich phases, and adiabatic cooling as a result of pressure loss. Modeling such behavior is a complex task. Only recently has a multiphase flow simulator been developed that handles the entire range of such thermodynamic conditions, but application so far has been limited to simple test cases (Pruess, 2004). A series of hypothetical, yet realistic scenarios with fast CO2 pathways should be modeled, while capturing as much “thermodynamics” as possible. Such studies would serve to gain a better understanding of the fluid flow and heat transfer processes that would accompany CO2 migration away from the primary storage reservoir, towards shallow depths and ultimately to the land surface. Some of these processes are beneficial in that they prevent or retard upward migration (e.g., through attenuation in multi-layer systems; energy losses through adiabatic cooling), others may enhance CO2 upflow (e.g., through stress-induced increases in fault permeability; reduced phase interference with water as CO2 saturation increases).        3. There is rather inconclusive evidence from natural analogues that CO2 presence could lead to pneumatic eruptions, i.e., self-enhancing, violent CO2 releases driven by high-pressure gas (Giggenbach et al., 1991; Benson et al., 2002). As opposed to the well-understood hydrothermal eruptions, where depressurization of a hot water reservoir may cause buoyant runaway of steam, pneumatic eruptions would not require substantial contributions of thermal energy. Pneumatic eruptions would be particularly harmful if occurring close to the land surface, which requires the accumulation of a large CO2 volume pressurized in a secondary storage reservoir. A self-enhancing, possibly eruptive escape of CO2 could be initiated by a sudden pressure loss in combination with the opening of a permeable pathway, as triggered, for example, by a seismic event, pressure-induced fracturing, or the drilling of a water-well into the reservoir. CO2 present as a separate gas phase would move upward by buoyancy forces and pressure differences. CO2 dissolved in water would be subject to rapid degassing following depressurization, which could result in an eruption of rising, expanding bubbles. It is not clear at present whether such pneumatic eruptions are possible under thermodynamic and hydrogeologic conditions representative of CO2 injection sites. Numerical modeling studies covering a wide range of realistic to extreme scenarios could help determine the risks and consequences of pneumatic eruptions, and could evaluate whether such events are possible for designated storage sites.  Conclusions Natural analogues with significant CO2 discharges at the land surface have been evaluated to identify case scenarios and related modeling needs in support of risk assessment for geological storage of CO2. The focus is on conditions that could generate large, possibly self-Abstract GHGT-8  3 enhancing, or even eruptive release events. We discuss three areas where further numerical analyses would be beneficial, and will present some example simulations. References  Benson S.M., R. Hepple, J. Apps, C.F. Tsang, and Lippmann, M., 2002, Lessons learned from natural and industrial analogs for storage of carbon dioxide in deep geological formations. Lawrence Berkeley National Laboratory Report LBNL-51170, Berkeley CA, 2002. Giggenbach W.F., Y. Sano, and H.U. Schmincke, 1991.  CO2-rich Gases from Lakes Nyos and Monoun, Cameroon; Lacher See, Germany; Dieng, Indonesia, and Mt. Gambier, Australia – Variations on a Common Theme. J. Volcanol. Geotherm. Res., Vol. 45, pp. 311 - 323. Pruess K., 2004: Numerical simulation of CO2 leakage from a geologic disposal reservoir, including transitions from super to sub-critical conditions, and boiling of liquid CO2. Soc. Pet. Eng. J., June 2004, pp. 237 - 248.  Table 1 Summary of natural analogs with large releases of CO2 Site CO2 Source Geologic model for accumulation Event triggering leakage Pathway for leakage Type of release Mammoth Mountain, CA USA Magmatic + thermal decomposition of carbonates Accumulation at ~2 km depth in porous/fractured rock under caprock Dike injection and seismic activity Faults and fractures Fast, diffuse, vent, spring Solfatara, Italy Magmatic + thermal decomposition of carbonates Relatively shallow zone of  fractured rock contains gas phase and overlies aquifers, then magma body at several km depth No specific release event captured Faults and fractures Diffuse and vent Mátraderecske, Hungary Geothermal/copper-zinc mineralization CO2 accumulates in karst water reservoir (~1 km depth) No specific release event captured Faults and fractures Diffuse, vent, spring Latera caldera, Italy  Thermal decomposition of carbonates CO2 accumulates in liquid-dominated, carbonate geothermal reservoir  capped by hydrothermally altered volcanics No specific release event captured Faults and fractures Diffuse, vent, spring Albani Hills, Italy Magmatic + thermal decomposition of carbonates Deep pressurized reservoirs in structural highs of sedimentary bedrock Slow leakage, plus sudden large releases possibly triggered by seismic activity  Faults and fractures Fast, diffuse, vent, and spring/well Dieng, Indonesia Magmatic Unknown Volcanic, possibly “pneumatic” eruptions Fissure Eruptive Abstract GHGT-8  4 Rabaul, Papua New Guinea Magmatic Unknown Unknown Fractures Fast, vent Lakes Monoun and Nyos, Camaroon Magmatic Accumulation in deep lake and stable stratification Rapid lake turnover  triggered at Monoun by landslide; Nyos trigger unknown NA Eruptive Laacher See, Germany Magmatic NA Seasonal lake overturn and mixing NA Diffuse and bubbling from lake surface, diffuse from lake shore Clear Lake, CA, USA Thermal decomposition of metasedimentary rocks, minor magmatic component CO2 derived from liquid-dominated geothermal reservoir hosted in marine metasedimentary rocks No specific release event captured Faults and fractures Gas vents, springs Paradox Basin, UT, USA Thermal decomposition of carbonates Reservoirs are vertically stacked, sandstone units, in fault-bounded anticlinal folds, capped by shale/siltstone units  No specific release event captured Faults and fractures Diffuse, gas seeps, springs Florina Basin, Greece Thermal decomposition of carbonates Reservoirs are vertically stacked, limestone and sandstone units, capped by silts and clays. No specific release event captured Slow leakage along rock discontinuities Springs, gas seeps       

Evaluating Potential for Large Releases from CO2 StorageReservoirs: Analogs, Scenarios, and Modeling Needs

Tsang, Chin-Fu

eScholarship - University of California

Lawrence Berkeley National LaboratoryLawrence Berkeley National LaboratoryTitleEvaluating Potential for Large Releases from CO2 Storage Reservoirs: Analogs, Scenarios, and Modeling NeedsPermalinkhttps://escholarship.org/uc/item/34w328kfAuthorsBirkholzer, JensPruess, KarstenLewicki, Jenniferet al.Publication Date2005-09-19eScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaAbstract GHGT-8  1 Evaluating Potential for Large Releases from CO2 Storage Reservoirs:  Analogues, Scenarios, and Modeling Needs Jens Birkholzer*1, Karsten Pruess1, Jennifer Lewicki1,  Chin-Fu Tsang1, Anhar Karimjee2 1Lawrence Berkeley National Laboratory,  Berkeley, CA, USA  2U.S. Environmental Protection Agency,  Washington D.C., USA Introduction While the purpose of geologic storage of CO2 in deep saline formations is to trap greenhouse gases underground, the potential exists for CO2 to escape from the target reservoir, migrate upward along permeable pathways, and discharge at the land surface. Such discharge is not necessarily a serious concern, as CO2 is a naturally abundant and relatively benign gas in low concentrations. However, there is a potential risk to health, safety and environment (HSE) in the event that large localized fluxes of CO2 were to occur at the land surface, especially where CO2 could accumulate. In this paper, we develop possible scenarios for large CO2 fluxes based on the analysis of natural analogues, where large releases of gas have been observed. We are particularly interested in scenarios which could generate sudden, possibly self-enhancing, or even eruptive release events. The probability for such events may be low, but the circumstances under which they might occur and potential consequences need to be evaluated in order to design appropriate site selection and risk management strategies. Numerical modeling of hypothetical test cases is needed to determine critical conditions for such events, to evaluate whether such conditions may be possible at designated storage sites, and, if applicable, to evaluate the potential HSE impacts of such events and design appropriate mitigation strategies. Methodology and Results Various natural analogues with large releases of CO2 have been evaluated, placing emphasis on the geologic model for CO2 accumulation, processes leading to the releases of CO2, pathways for migration, and type of release at the surface. Table 1 gives a summary of these analogues and their characteristics. While detailed information on geologic models of accumulation or on migration pathways is often unavailable, a few general conclusions can be drawn with respect to release scenarios and modeling studies important for the risk assessment of geologic storage of CO2.  1. Large releases often originate from natural CO2 plumes that have risen from depth and accumulated under low-permeability caprock. This suggests that the possibility of large CO2 discharges at the land surface is not necessarily linked to fast release from the primary storage formation. In fact, the length of the flow pathway from depth and various mitigating effects make such a scenario rather unlikely. Conditions more conducive to a large, sudden release would involve accumulation of slowly leaking CO2 in a secondary formation closer to the land surface. Suitable conditions could be provided by an anticlinal                                                  * Corresponding Author: jtbirkholzer@lbl.gov, +1 510 486 7134 Abstract GHGT-8  2 structure with a good caprock, where CO2 can accumulate until it reaches a spillpoint. It is thus important to consider the potential for secondary storage reservoirs in a site evaluation and, if applicable, to determine the accumulation and possible release of CO2 from such secondary reservoirs in numerical modeling studies. 2. Faults and fracture zones are the main pathways for gas migration in most natural analogues with large CO2 discharge. It is thus mandatory to be able to predict qualitatively and quantitatively the fast upward flow of CO2 in high-permeability zones that may extend from depth to surface. It is possible that such pathways are generated during or after injection by disruptive events related to geomechanical failures or seismic activity. During upward migration, CO2 is affected by transitions from super- to sub-critical conditions, by phase changes between liquid and gaseous CO2, phase partitioning between water-rich and CO2-rich phases, and adiabatic cooling as a result of pressure loss. Modeling such behavior is a complex task. Only recently has a multiphase flow simulator been developed that handles the entire range of such thermodynamic conditions, but application so far has been limited to simple test cases (Pruess, 2004). A series of hypothetical, yet realistic scenarios with fast CO2 pathways should be modeled, while capturing as much “thermodynamics” as possible. Such studies would serve to gain a better understanding of the fluid flow and heat transfer processes that would accompany CO2 migration away from the primary storage reservoir, towards shallow depths and ultimately to the land surface. Some of these processes are beneficial in that they prevent or retard upward migration (e.g., through attenuation in multi-layer systems; energy losses through adiabatic cooling), others may enhance CO2 upflow (e.g., through stress-induced increases in fault permeability; reduced phase interference with water as CO2 saturation increases).        3. There is rather inconclusive evidence from natural analogues that CO2 presence could lead to pneumatic eruptions, i.e., self-enhancing, violent CO2 releases driven by high-pressure gas (Giggenbach et al., 1991; Benson et al., 2002). As opposed to the well-understood hydrothermal eruptions, where depressurization of a hot water reservoir may cause buoyant runaway of steam, pneumatic eruptions would not require substantial contributions of thermal energy. Pneumatic eruptions would be particularly harmful if occurring close to the land surface, which requires the accumulation of a large CO2 volume pressurized in a secondary storage reservoir. A self-enhancing, possibly eruptive escape of CO2 could be initiated by a sudden pressure loss in combination with the opening of a permeable pathway, as triggered, for example, by a seismic event, pressure-induced fracturing, or the drilling of a water-well into the reservoir. CO2 present as a separate gas phase would move upward by buoyancy forces and pressure differences. CO2 dissolved in water would be subject to rapid degassing following depressurization, which could result in an eruption of rising, expanding bubbles. It is not clear at present whether such pneumatic eruptions are possible under thermodynamic and hydrogeologic conditions representative of CO2 injection sites. Numerical modeling studies covering a wide range of realistic to extreme scenarios could help determine the risks and consequences of pneumatic eruptions, and could evaluate whether such events are possible for designated storage sites.  Conclusions Natural analogues with significant CO2 discharges at the land surface have been evaluated to identify case scenarios and related modeling needs in support of risk assessment for geological storage of CO2. The focus is on conditions that could generate large, possibly self-Abstract GHGT-8  3 enhancing, or even eruptive release events. We discuss three areas where further numerical analyses would be beneficial, and will present some example simulations. References  Benson S.M., R. Hepple, J. Apps, C.F. Tsang, and Lippmann, M., 2002, Lessons learned from natural and industrial analogs for storage of carbon dioxide in deep geological formations. Lawrence Berkeley National Laboratory Report LBNL-51170, Berkeley CA, 2002. Giggenbach W.F., Y. Sano, and H.U. Schmincke, 1991.  CO2-rich Gases from Lakes Nyos and Monoun, Cameroon; Lacher See, Germany; Dieng, Indonesia, and Mt. Gambier, Australia – Variations on a Common Theme. J. Volcanol. Geotherm. Res., Vol. 45, pp. 311 - 323. Pruess K., 2004: Numerical simulation of CO2 leakage from a geologic disposal reservoir, including transitions from super to sub-critical conditions, and boiling of liquid CO2. Soc. Pet. Eng. J., June 2004, pp. 237 - 248.  Table 1 Summary of natural analogs with large releases of CO2 Site CO2 Source Geologic model for accumulation Event triggering leakage Pathway for leakage Type of release Mammoth Mountain, CA USA Magmatic + thermal decomposition of carbonates Accumulation at ~2 km depth in porous/fractured rock under caprock Dike injection and seismic activity Faults and fractures Fast, diffuse, vent, spring Solfatara, Italy Magmatic + thermal decomposition of carbonates Relatively shallow zone of  fractured rock contains gas phase and overlies aquifers, then magma body at several km depth No specific release event captured Faults and fractures Diffuse and vent Mátraderecske, Hungary Geothermal/copper-zinc mineralization CO2 accumulates in karst water reservoir (~1 km depth) No specific release event captured Faults and fractures Diffuse, vent, spring Latera caldera, Italy  Thermal decomposition of carbonates CO2 accumulates in liquid-dominated, carbonate geothermal reservoir  capped by hydrothermally altered volcanics No specific release event captured Faults and fractures Diffuse, vent, spring Albani Hills, Italy Magmatic + thermal decomposition of carbonates Deep pressurized reservoirs in structural highs of sedimentary bedrock Slow leakage, plus sudden large releases possibly triggered by seismic activity  Faults and fractures Fast, diffuse, vent, and spring/well Dieng, Indonesia Magmatic Unknown Volcanic, possibly “pneumatic” eruptions Fissure Eruptive Abstract GHGT-8  4 Rabaul, Papua New Guinea Magmatic Unknown Unknown Fractures Fast, vent Lakes Monoun and Nyos, Camaroon Magmatic Accumulation in deep lake and stable stratification Rapid lake turnover  triggered at Monoun by landslide; Nyos trigger unknown NA Eruptive Laacher See, Germany Magmatic NA Seasonal lake overturn and mixing NA Diffuse and bubbling from lake surface, diffuse from lake shore Clear Lake, CA, USA Thermal decomposition of metasedimentary rocks, minor magmatic component CO2 derived from liquid-dominated geothermal reservoir hosted in marine metasedimentary rocks No specific release event captured Faults and fractures Gas vents, springs Paradox Basin, UT, USA Thermal decomposition of carbonates Reservoirs are vertically stacked, sandstone units, in fault-bounded anticlinal folds, capped by shale/siltstone units  No specific release event captured Faults and fractures Diffuse, gas seeps, springs Florina Basin, Greece Thermal decomposition of carbonates Reservoirs are vertically stacked, limestone and sandstone units, capped by silts and clays. No specific release event captured Slow leakage along rock discontinuities Springs, gas seeps       

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Evaluating Potential for Large Releases from CO2 Storage Reservoirs: Analogs, Scenarios, 
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Evaluating Potential for Large Releases from CO2 StorageReservoirs: Analogs, Scenarios, and Modeling Needs

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