Seismic modelling and monitoring of carbon storage in a sandstone aquifer

Virginia Cecilia Vera, Donald C. Lawton

Carbon Management Canada in association with CREWES have invested in research projects that investigates the feasibility of injecting and monitoring reduced amounts of CO₂ in sandstone aquifers in Alberta. In this case the target is a "shallow" layer of Paskapoo Formation sandstone located southwest of Calgary. In order to evaluate the monitoring viability, Gassmann fluid substitution and 3D seismic modeling were undertaken. Synthetic seismograms were generated to assess changes given the injection of CO₂ in Lower Paskapoo sandstone. The resulting model attempts to represent the study site and its geology, therefore the seismic data acquired during 2010 field school was used as a guide. Figure 1 shows the resulting model and seismic survey. Using Norsar3D software, a pre-injection model and a post-injection scenario, which include the CO₂ plume, were obtained. The plume was estimated for a 3000 tons of CO₂, which is the expected injection amount after 3 years, and 50% saturation. The plume size and shape was calculated taking into account the volumetric principles and the simulation of a radial dispersion. From the resulting seismic volumes it is possible to interpret a difference in seismic amplitude and also a time delay of the reflectors in the injection zone and beneath it. The changes caused by the presence of CO₂ are easily recognizable applying a subtraction of the post-injection model to the initial model. Figure 2 is the 3D volume after the subtraction of the models, showing the anomaly after injection of CO₂.