Natural and industrial analogues for leakage of CO2 from storagereservoirs: identification of features, events, and processes and lessonslearned
The injection and storage of anthropogenic CO2 in deepgeologic formations is a potentially feasible strategy to reduce CO2emissions and atmospheric concentrations. While the purpose of geologiccarbon storage is to trap CO2 underground, CO2 could migrate away fromthe storage site into the shallow subsurface and atmosphere if permeablepathways such as well bores or faults are present. Large-magnitudereleases of CO2 have occurred naturally from geologic reservoirs innumerous volcanic, geothermal, and sedimentary basin settings. Carbondioxide and natural gas have also been released from geologic CO2reservoirs and natural gas storage facilities, respectively, due toinfluences such as well defects and injection/withdrawal processes. Thesesystems serve as natural and industrial analogues for the potentialrelease of CO2 from geologic storage reservoirs and provide importantinformation about the key features, events, and processes (FEPs) that areassociated with releases, as well as the health, safety, andenvironmental consequences of releases and mitigation efforts that can beapplied. We describe a range of natural releases of CO2 and industrialreleases of CO2 and natural gas in the context of these characteristics.Based on this analysis, several key conclusions can be drawn, and lessonscan be learned for geologic carbon storage. First, CO2 can bothaccumulate beneath, and be released from, primary and secondaryreservoirs with capping units located at a wide range of depths. Bothprimary and secondary reservoir entrapments for CO2 should therefore bewell characterized at storage sites. Second, many natural releases of CO2have been correlated with a specific event that triggered the release,such as magmatic fluid intrusion or seismic activity. The potential forprocesses that could cause geomechanical damage to sealing cap rocks andtrigger the release of CO2 from a storage reservoir should be evaluated.Third, unsealed fault and fracture zones may act as fast and directconduits for CO2 flow from depth to the surface. Risk assessment shouldtherefore emphasize determining the potential for and nature of CO2migration along these structures. Fourth, wells that are structurallyunsound have the potential to rapidly release large quantities of CO2 tothe atmosphere. Risk assessment should therefore be focused on thepotential for both active and abandoned wells at storage sites totransport CO2 to the surface, particularly at sites with depleted oil orgas reservoirs where wellsare abundant. Fifth, the style of CO2 releaseat the surface varies widely between and within different leakage sites.In rare circumstances, the release of CO2 can be a self-enhancing and/oreruptive process; this possibility should be assessed in the case of CO2leakage from storage reservoirs. Sixth, the hazard to human health hasbeen small in most cases of large surface releases of CO2. This could bedue to implementation of public education and CO2 monitoring programs;these programs should therefore be employed to minimize potential health,safety, and environmental effects associated with CO2 leakage. Finally,while changes in groundwater chemistry were related to CO2 leakage due toacidification and interaction with host rocks along flow paths, watersremained potable in most cases. Groundwaters should be monitored forchanges that may be associated with storage reservoirleakage.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director, Office of Science; Environmental ProtectionAgency
- DOE Contract Number:
- DE-AC02-05CH11231; EPA:DE-AC02-05CH11231
- OSTI ID:
- 919752
- Report Number(s):
- LBNL-59784; R&D Project: G4W009; BnR: 400408000; TRN: US200822%%516
- Journal Information:
- Environmental Geology, Vol. 52, Issue 3; Related Information: Journal Publication Date: 04/2007
- Country of Publication:
- United States
- Language:
- English
Similar Records
NRAP-Open-IAM: NRAP Open Source Integrated Assessment Model
Surface CO2 leakage during the first shallow subsurface CO2release experiment