Newly emerging cases of hydraulic fracturing induced seismicity in the Duvernay East Shale Basin

• Published in: Tectonophysics 2020-03, Vol.779, p.228393, Article 228393
• Main Authors: Schultz, Ryan, Wang, Ruijia
• Format: Article
• Language: English
• Subjects: Activation; Centroids; Clusters; Coastal inlets; Duvernay Formation; Earthquakes; Geology; Horizontal wells; Hydraulic fracturing; Induced seismicity; Mountains; Recovering; Sedimentary rocks; Seismic activity; Seismicity; Shale; Shales; Slip; Structural geology; Tensors; Waveforms
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2020.228393

Hydraulic fracturing (HF) in the Duvernay Formation near Fox Creek, Alberta, Canada, has produced some of the most prolific clusters of induced seismicity. In this paper, we describe newly emerging clusters of events occurring in previously quiescent (and undeveloped) areas of the Duvernay Formation. In the Duvernay East Shale Basin, an industry supplemented waveform database is examined using a variety of seismological techniques. Here, strike-slip events as large as 4.18 ML have been felt in nearby cities. Temporal relationships suggest these clusters are almost certainly (>99.7% confidence) caused by nearby HF. Spatially, these earthquakes tend to occur in the strata directly overlying the Duvernay Formation and laterally near a horizontal well. One exceptional cluster clearly delineates a 1.5 km offset between its centroid and the inducing horizontal well, raising questions about the earthquake triggering mechanism. Westward in the Duvernay, two minor clusters within the Willesden Green region appear to be tenuously related to HF completions. This study also places constraints on the structural geology of faulting occurring in the Rocky Mountain House Seismogenic Zone – a region of induced seismicity related to secondary recovery in the Strachan D-3A pool. Here, our moment tensors and double difference relocations describe thrust-slip on a fault underlying the target formation. Last, the largest event (4.27 ML) in our study area was likely natural, due to its deeper hypocentral depth (~15 km) and non-correspondence with industrial operations. Overall, the newly emerging clusters are consistent with reactivation of basement rooted faults. •Hydraulic fracturing induced earthquakes are occurring in a new portion of the Duvernay, following industry development in the East Shale Basin.•Magnitude ‘jumps’ (+2.0 ML) are observed in the sequence of the largest events, raising questions about effective management.•A case with 1.5 km between cluster epicenter and well lateral is one of the clearest and largest delineations of spatial separation, to date.•The majority of events are located just above the target formation, with some as deep as the crystalline basement.