TITLE: Leakage detection strategies for atmospheric monitoring of CO2 at geosequestration facilities

ABSTRACT: Geological carbon storage appears likely to form an integral part of our emissions reduction effort. The principal risk associated with carbon storage is leakage of CO2 back to the atmosphere. Concern about leakage operates at two levels: catastrophic leakage in which local CO2 concentrations might reach levels dangerous to humans and ecosystems (>1%) and relatively small, persistent leaks that may compromise the effectiveness of carbon storage as a climate change mitigation strategy. This work focuses on the second of these concerns. Due to the large and varying background concentration of CO2, detection of non-catastrophic leakage is a difficult proposition.

As a regulated carbon economy becomes more likely, it will be necessary to place rigorous detection limits on the techniques used to monitor potential CO2 leakage from geological storage sites. In addition to detection of leaks, an atmospheric monitoring scheme must ideally be able to identify the provenance of gas inducing abnormal rises in concentration and ultimately quantify the size of significant leaks.

This talk will describe work we have been doing aimed at quantifying what realistic detection limits are for this task. It will show how the use of tracers can improve both detection sensitivity and certainty of attribution to a particular source and will include some examples of our monitoring strategy in action at the demonstration geological CO2 storage facility, the Otway Basin Pilot Project, in southwest Victoria, Australia.