Simple and effective atmospheric monitoring for CO2 leakage

• We implemented an array of atmospheric sensors around a controlled release of CO2.
• Atmospheric tomography was used to locate the release.
• We estimate we could detect a leak of 0.4 tonne per day of CO2.

The ultimate purpose of carbon capture and storage is to keep CO2 out of the atmosphere. However there are some scenarios in which leakage to atmosphere may occur. Because of the large and variable level of naturally-occurring CO2, and rapid dispersion in the atmosphere, leakage to atmosphere can be difficult to detect from concentration measurements. By using prior information from risk assessments about plausible location of leaks, it is possible to design simple yet effective systems for identifying the location of a leak within a pre-defined area of surveillance. We have designed an inexpensive system of autonomous sensors and inversion methods that can locate leaks of CO2 and have tested it during a controlled release at the CO2CRC Otway site. We have implemented a Bayesian inversion method, and carefully modelled the various error sources, to quantify the detection limit of the complete system. The combination of methodologies proved effective and it, and its associated workflow, could be adapted and implemented in a variety of storage settings.