Sparse seismic monitoring at CMC’s Newell County CO₂ storage facility

Brendan Kolkman-Quinn, Donald C. Lawton, Malcolm B. Bertram, Marie Macquet

Active-source seismic monitoring provides crucial Measurement, Monitoring, and Verification (MMV) data for Geological CO₂ Storage (GCS). Conventional 2D and 3Dsurface seismic monitoring of GCS becomes prohibitively expensive for CO₂ plumes extending over 10s of kilometers, particularly at storage hubs operating on the scale of 100– 1000 Mt of injection. Sparsely distributed, automated monitoring nodes with permanently installed sources and receivers can provide active monitoring capability overlarge areas by using sparse seismic reflection points to detect injection-related changes in the subsurface over time. Seismic receivers at each sparse node simultaneously provide passive monitoring capability for injection-related microseismicity and induced seismicity.Source and receiver repeatability is crucial in the case of sparse monitoring. Field tests of seismic sources on a permanent source location were performed at Carbon Management Canada’s (CMC) CO₂ storage pilot site in Newell County, Alberta, Canada. The source location is a steel pile screwed through 24.7 m of unconsolidated glacial till, allowing the pile’s toe to act as a point source coupled with sedimentary bedrock. Impulsive and vibrational seismic signals were successfully transmitted through the steel pile and recorded on borehole and buried seismic sensors, bypassing the highly attenuative and non-stationary filtering effects of the near-surface. A maximum frequency of 180 Hz was consistently observed in each source test, likely caused by attenuation within the geology between the pile toe and the borehole receivers. With the goal of automating shots and recordings, field tests achieved proof of concept for synchronized source and recording trigger systems, independently controlled by GPS timing. The installation of two additional screw pile permanent source locations at the Newell County Facility is planned for the end of 2023, with the long term objective of automated, daily monitoring of the CO₂ plume starting in 2024.