This study demonstrates that geologic structure can significantly alter stresses within the completion zone and change the characteristics of microseismicity. Completions and microseismic data are used to examine the effects of geologic structure on an executed completions program. The microseismic was recorded on a 98-station near-surface array for approximately 200 stages on 7 wells. Two prominent faults are identified using microseismic data. The differences between microseismic event populations from hydraulic fracture stimulation and fault reactivation are assessed in terms of event source mechanisms and event parameters.
We examine changes in calculated bottomhole instantaneous shut-in pressure (ISIP) gradient near faults and the associated change in microseismic behavior. Stress regime, maximum horizontal stress (SHmax) directions and stress magnitudes along faults are examined with a stress inversion approach using source mechanism information.
Results show that hydraulic fractures, particularly in the Muskwa shales, have high b-values and tend to be characterized by dip-slip failures. Events relating to fault reactivation are characterized by strike-slip events and have low b-values. The orientations of SHmax derived from stress inversion for fault populations align with regional SHmax estimates from regional borehole breakout measurements. Stages intersected by prominent faults show significant increases in measured ISIP, which are more pronounced in the Evie completion zone.