Seismic modelling of CO₂ in a sandstone aquifer, Priddis, Alberta

Virginia Cecilia Vera

The CO₂ storage potential of a shallow sandstone layer of the Paskapoo Formation, southwest of Calgary, was evaluated in this thesis. In order to assess the CO₂ monitoring viability, Gassmann fluid substitution was undertaken, followed by 2D and 3D seismic modeling in the study area. From the Gassmann approach, considerable changes of velocity and density were found with increasing CO₂ saturation. In addition, Amplitude versus offset (AVO) analysis proved to be sensitive for detecting saturation changes, especially through the evaluation of Shuey's parameters. From the seismic modelled volumes, a difference in seismic amplitude was recognized. As well, time delays of the reflectors in the injection zone and below were measured. The reflectivity coefficient decreased approximately 30% and the time delay is about 1 ms. The changes caused by the presence of CO₂ are identifiable by subtracting the monitor model data from the baseline model data. These models and simulations demonstrate the feasibility of using the Basal Paskapoo Fm. as a CO₂ storage site, given its petrophysical, stratigraphic and geological characteristics. The proposed amount of CO₂ injection is 3000 tonnes (5 injections of 600 tonnes each), a mass that can be resolved using the seismic method. Following volumetric calculations and seismic parameters it was possible to postulate that 300 tonnes of CO₂ could be detected by time-lapse seismic analysis.