Induced Seismicity Characterization during Hydraulic-Fracture Monitoring with a Shallow-Wellbore Geophone Array and Broadband Sensors

The Tony Creek Dual Microseismic Experiment (ToC2ME) is a field program that used a diverse set of sensors to record a hydraulic-fracturing completion program at a four-well pad west of Fox Creek, Alberta. The acquisition systems consisted of a 68-station shallow borehole array, six broadband seismometers, and one strong-motion accelerometer. This dataset yielded above 4000 events with well-determined magnitudes and hypocenters, with a maximum magnitude of M-w 3.2. The geophones, with a 10-Hz natural frequency, are found to be more suitable for determining event magnitudes below M-w 1.0; seismometers are more suitable above this magnitude. The largest events have strike-slip mechanisms and are clustered above the treatment zone along well-defined north- south lineaments. Several other event clusters are more diffuse and have distinct magnitude characteristics and mechanisms. Horizons extracted from 3D reflection seismic data reveal structural fabrics that are subparallel to event clusters, although the microseismic lineaments do not appear to correlate exactly with seismically imaged features.