Geochemical Monitoring

Techniques for monitoring CO2 for health and safety reasons and as a measure of biological activity are well established. However, further research is necessary to enable detection of small concentrations of CO2 over large areas which is needed to monitor CO2 storage sites.

• Geochemical Monitoring

  This involves regular testing of the soil, groundwater and the subsurface around the storage site for changes in the content of CO2 and other associated gases (methane, oxygen and nitrogen). CO2 release directly above a storage site can be measured using infra-red gas analysers.

• Remote Sensing

  Several remote sensing techniques are also under development including LIDAR and satellite based systems.

• Tracers

  Natural tracers (the isotopes of C, O, H and noble gases) and artificial tracers (noble gases, SF6 and perfluorocarbons) could also help detect CO2 migration into the groundwater. Tracers can be used to give the injected CO2 a distinct fingerprint distinguishing it from the natural CO2 already present in the subsurface. For example perfluorocarbons can be detected at concentrations as low as 1 part per trillion.

With all geochemical methods it is essential that a baseline survey is carried out prior to CO2 injection to assess the geochemistry of the site. This will allow any changes caused by CO2 injection to be determined.