Vol 2 Chapter 24: The Use of Noble Gas Isotopes for Monitoring Leakage of Geologically Stored CO2
Gregory J. Nimz and G. Bryant Hudson
Abstract: One of the primary concerns in CO2 storage is monitoring the storage site on a long-term basis for possible leakage of CO2. Concentrations of CO2 vary widely in the Earth’s crust, making detection of very small releases difficult. Small amounts of noble gas isotopes can be dissolved into the CO2 being injected for storage and used as tracers to monitor CO2 movement. Noble gases are chemically inert, environmentally safe, and are persistent and stable in the environment. The unique isotopic compositions that can be imparted to the CO2 can be unambiguously identified during monitoring. Among the noble gases, xenon isotopes have commercial costs and availability suitable for use in large CO2 storage operations. Required xenon volumes are low, simplifying handling and injection. Multiple batches of injected CO2 at the same site could be imparted with different xenon isotopic compositions, making each of them identifiable with only a single xenon analysis. These characteristics are believed to make xenon a superior tracer to other option, SF6 and 14 CO2 . A case study in noble gas tracing at the Mabee Enhanced Oil Recovery field in West Texas indicates that unique noble gas isotopic compositions within a CO2 injection stream can be detected and readily identified in outlying wells, and that noble gas behavior in a CO2 storage setting will be systematic and predictable.
Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO2 Capture
Project Geologic Storage of Carbon Dioxide with Monitoring and Verification - Volume 2
Edited by: Sally M. Benson, Lawrence Berkeley Laboratory, Berkeley, CA, USA
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