Abby L. Harvey
GHG Monitor
10/9/2015
Researchers at the Scottish Universities Environmental Research Centre have discovered a new process by which they can “fingerprint” carbon stored underground to monitor the movement of the plumes, according to a new paper published this week in International Journal of Greenhouse Gas Control.
The “fingerprint” is developed by measuring traces of helium, neon, and argon to monitor the stored CO2. The researchers said the stable carbon isotope composition of CO2 has in the past been widely used to track the injected gas; however, if the isotope of the injected CO2 is too similar to the CO2 already in place in the reservoir, that process becomes less efficient.
Thus, tracing the CO2 by its noble gas fingerprint offers an additional option for tracking the movement of the injected CO2 if monitoring via the CO2 isotope is not an option, the researchers found. Through this new tracking process, it will be possible to better discern the movements and interactions of CO2 plumes underground in a larger variety of conditions.
“The noble gases are present in trace amounts in natural CO2. Where the isotopic composition of the noble gases in injected natural CO2 are significantly different to those of the in-place reservoir gas they have the potential to trace the movement and mixing of the injected gas,” the report says.
To study the utility of the noble gas fingerprint of injected CO2, the researchers applied the new process to an enhanced oil field operated by Denbury Resources in Cranfield, Miss., for three years.
“The unique noble gas isotope composition of the Jackson Dome CO2 injected in the Cranfield CO2-EOR field permits evaluation of the effectiveness of using [helium, neon, and argon] isotopes to trace injected CO2,” according to the report. “The isotopic compositions of production well gases sampled in 2009 and 2012, 19 and 45 months after the start of CO2 injection define binary mixtures between injected gas and the in-place reservoir gas. This allows the noble gas isotopic composition of the reservoir gas to be determined.”
