CaMI Field Research Station, Alberta, Canada: Feasibility study for time lapse seismic monitoring and ambient noise correlation

Reducing GHG emissions is a major global challenge. GHG capture, utilization and storage is a successful and important method for achieving international commitments. The Containment and Monitoring Institute (CaMI) of CMC Research Institutes Inc. (CMC), in collaboration with the University of Calgary, has developed a comprehensive Field Research Station (FRS) in southern Alberta, Canada. The purpose of CaMI.FRS is to develop innovative technologies to prevent and monitor early leakages of a deeper, large-scale CO₂ reservoir. To simulate a leakage, a small amount of CO₂ (<500 t/year over 5 years) will be injected a shallow surface (300 m depth).

To detect and monitor the injected CO₂, different geochemical and geophysical instruments are in place, both on the surface and along monitoring wells. A non-exhaustive list of geophysical instruments includes a DAS permanently installed, VSP experiments with downhole geophones, and a permanent 10x10 array of buried 3C geophones (10m spacing, buried at 1m) with permanent installed sources. Over the past year, 4 active surveys were acquired to characterize the near surface effects in this extremely-variable weather conditions site. Pressure and temperature gauges at the top and bottom of the injection well as well as DTS along it are also installed.

We produce a feasibility study for time-lapse monitoring using surface active seismic survey. Results are dependent of the saturation behavior between brine and injected CO₂: if we assume a semi-patchy saturation, the modelling shows that the detection threshold is 250 tons of injected gas. If we assume uniform saturation, then we predict that the plume should be detectable by seismic methods as soon as after 1 year of injection. Full patchy saturation is a more challenging condition and it may take several years of injection for the plume to be detectable using surface seismic data.

In addition to active surveys, ambient noise was also recorded (October 2017 and February 2018, before starting the main injection phase) and preliminary work on ambient noise correlation shows very stable results in the daily correlation waveform. Variations in the elastic parameters due to CO₂ will directly affect the correlation waveform, and passive recording after CO₂ injection should allow us to detect the effect of the injection on the correlations.