Seismic monitoring using compact phased arrays: CO2 sequestration monitoring

Abstract

A network of passive, persistent, permanent, compact volumetric phased arrays (e.g. SADAR® arrays, Nyffenegger et al., 2022) features multiple technical advantages for monitoring seismic activity at and around CO2 injection and storage sites compared to a traditional surface network or downhole sensor strings at the depth of a reservoir. A limited demonstration network was installed at Carbon Management Canada’s (CMC) Containment and Monitoring Institute (CaMI) Field Research Station, and analysis of the acquired data has produced an event bulletin covering ∼80 days. Coherent processing (i.e. beamforming) of the acquired data increases the SNR allowing detection and localization of 406 subsurface microseismic events down to moment magnitude Mw = -3 within the network geographical extent. Analyst vetting of these events indicates that the signals typically exhibit clear onset of P waves in the optimal beam, enabling arrival time picking with a lower uncertainty than for the shear waves that dominate the records observed by other surface networks. In addition, using the optimal beam attributes associated to the event phase arrivals allows identifying signals arriving from below and exterior to the network’s coverage (e.g., episodic low-frequency tremor), potentially associated with other natural or man-made seismicity also worth monitoring.