Evolution of a deep CO2 plume from time-lapse seismic imaging at the Aquistore storage site, Saskatchewan, Canada

The Aquistore CO2 Storage Site in southeast Saskatchewan, Canada began CO2 injection in April 2015. CO2 is injected into a 3200 m-deep sandstone reservoir for long-term storage. 3D time-lapse seismic surveys have been acquired using a permanent sparse seismic array to monitor the CO2 plume. Time-lapse data have been acquired prior to CO2 injection (November 2013) and after injection of 36 kilotonnes (February 2016, Monitor 1), and 102 kilotonnes (November 2016, Monitor 2). 3D time-lapse seismic analyses reveal amplitude differences (nRMS of 0.10-0.25) within the reservoir that exceed the background noise-level (nRMS ∼ 0.03-0.04). These amplitude anomalies are interpreted as zones of CO2 saturation and are thus used to track/map the CO2 plume within the reservoir at these times. They show the development of a stratified CO2 plume that is spreading predominantly along NNW-SSE structural/permeability trends in the reservoir.