Enhanced Hydrogeochemical Baseline of a CO2 Injection Facility in Southern Alberta, Canada

Abstract

Geological storage of CO2 is anticipated to play a significant role in the management and reduction of greenhouse gas emissions. Monitoring of CO₂ injection facilities is essential to provide reassurance of the containment of the injected CO2. Here, we report results over six years (2018–2023) for a hydrogeological and geochemical (gas compositions, δ13CCH4, δ13CCO2, δ2HCH4 and noble gas concentration and isotopes) monitoring program at a small-scale CO2 injection facility located near Brooks, Alberta, Canada with injection ∼300 m below ground. The results provide a comprehensive record of the subsurface hydrological and geochemical conditions over the six-year period. Injected CO2 was not detected in samples from the injection zone. There was also no indication of injected CO2 in samples collected from surface casing vents of the three ∼300 m deep wells, nor was injected CO2 observed in samples from the six shallow groundwater wells (<105 m deep). Various compositional and isotopic changes have been observed over time which are interpreted to either be indirectly related to CO2 injection or completely unrelated indicating non-CO2 injection related variability in the baseline conditions of the site. Additionally, a progressive reduction in hydraulic head has been observed in some shallow aquifers consistent with drought conditions in the region. Our study implies that complex subsurface changes may occur at CO2 storage sites which may be unrelated to human activity, complicating the monitoring of CO2 injection