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In a new paper published in the International Journal of Greenhouse Gas Control, researchers describe how they have used the unique signature from traces of the noble gases - helium, neon and argon - to monitor the fate of CO₂ stored underground.
Carbon dioxide emissions from energy generation, in particular coal burning, contribute to the increasing pace of global climate change. Carbon capture and storage (CCS) techniques aim to store CO₂ in depleted oil and gas fields or deep aquifers, preventing it from reaching the atmosphere. Widespread use of CCS in the future could help to reduce global carbon emissions, helping to slow global temperature rise.
The paper’s authors, from the Scottish Universities Environmental Research Centre (SUERC), collected gas samples in 2009 and 2012 from wells at the Cranfield CO₂-enhanced oil recovery field in Mississippi, USA.
Co-author Professor Finlay Stuart of SUERC (University of Glasgow) said:
We have shown for the first time that the naturally occurring helium, neon and argon in the injected gas is a unique ‘fingerprint’ that can be used to monitor the movement of the CO₂, and determine how it is stored. Before CCS can become widely adopted as a method of CO₂ mitigation we need to know how effective the gas can be stored underground.
The noble gases are chemically inert so they are not affected by interactions with rocks or water in the way that carbon dioxide is, so they can be used to identify the physical processes that have affected the gas. They provide a cheap way to fingerprint injected gases in future large-scale carbon storage projects, and have the potential to provide a unique way to track the presence of deep shale gas and coal bed-derived methane in shallow aquifers during and after extraction.
Co-author of the study, Dr Stuart Gilfillan of the University of Edinburgh said:
We know that natural noble gas fingerprints allow us to find out how CO₂ is stored in natural reservoirs over millions of years, but this study now shows that these fingerprints can be used to track the movement and fate of injected CO₂ over much shorter periods relevant to CCS. This paves the way for the use of these inexpensive natural fingerprints in future CCS projects.
The team’s paper, Tracing injected CO₂ in the Cranfield enhanced oil recovery field (MS, USA) using He, Ne and Ar isotopes, is published in the International Journal of Greenhouse Gas Control. The research was supported by funding from the Engineering and Physical Sciences Research Council (EPSRC).
This story was published by the University of Glasgow on Monday 5 October. The University of Edinburgh is a partner institute of SCCS.