| Title | From seismic quiescence to surged activity after decades of wastewater disposal: a case study in central-west Alberta, Canada |
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| Author | Yu, H ; Kao, H; Visser, R; Wang, B |
| Source | Geophysical Research Letters vol. 48, issue 22, e2021GL095074, 2021 p. 1-11, https://doi.org/10.1029/2021GL095074 |
| Image |  |
| Year | 2021 |
| Alt Series | Natural Resources Canada, Contribution Series 20210340 |
| Publisher | American Geophysical Union |
| Document | serial |
| Lang. | English |
| Media | paper; digital; on-line |
| File format | pdf; html |
| Province | Alberta |
| NTS | 83L/07; 83L/08; 83L/09; 83L/10 |
| Area | Smoky River |
| Lat/Long WENS | -119.0000 -118.0000 54.6667 54.3333 |
| Subjects | geophysics; stratigraphy; Science and Technology; Nature and Environment; Economics and Industry; Health and Safety; earthquakes; earthquake risk; earthquake magnitudes; seismicity; seismic risk; liquid
waste disposal; waste disposal wells; groundwater regimes; stress analyses; fluid migration; bedrock geology; lithology; sedimentary rocks; reefs; structural features; faults; seismological network; stratigraphic nomenclature; hydrostratigraphic
units; Western Canada Sedimentary Basin; Duvernay Formation; Swan Hills Formation; Musreau Lake Sequence; Woodbend Aquitard; Waste water; Phanerozoic; Paleozoic; Devonian |
| Illustrations | location maps; geoscientific sketch maps; time series; stratigraphic charts; plots; schematic models |
| Program | Environmental Geoscience Shale Gas - induced seismicity |
| Released | 2021 10 28 |
| Abstract | Injection-induced earthquakes associated with wastewater disposal (WD) in the Western Canadian Sedimentary Basin are much fewer than those linked to hydraulic fracturing. Recently, 43 WD-related
earthquakes (M1.3-3.9) occurred in a historically seismically quiet area where long-term injections became intensive since 2018, foreshadowing a critical stress state accumulated from long-term injections. Our improved earthquake locations show that
the injection well targeting the deeper middle-upper Devonian aquifer system causes more vigorous seismicity with a wide range of stress drop values (0.8-230 MPa) compared to other shallower wells. Three physical mechanisms may collectively lead to
the observed seismic pattern: (a) the underlying Devonian reef system makes it easier for injected fluids to migrate horizontally, (b) fluids can be channeled into the widespread critical faults and migrate vertically to cause earthquakes along it,
and (c) aseismic slip probably triggered within the Duvernay formation by fluid migrating can further facilitate seismicity at shallower depths. |
| Summary | (Plain Language Summary, not published)
Earthquakes can be triggered during fluid injections. In the Western Canadian Sedimentary Basin, the operation of wastewater disposal appears to have
caused much fewer earthquakes than hydraulic fracturing. Recently, a sequence of 43 small-to-moderate-sized earthquakes occurred in a seismically quiet area, where injections have been safely operated for more than two decades prior to becoming
intensive in 2018. The refined earthquake distribution confirms that these earthquakes are related to disposal injections. Among the four active wells, the one with a deeper injection depth caused more earthquakes than other shallower wells. As the
injection of the deeper well is close to the ancient reef system, horizontal fluid migration is facilitated and more likely to reach nearby faults. Fluid migration along sub-vertical faults can cause deeper earthquakes in the basement and aseismic
creep in the overlying shale formation. The induced aseismic slip can further load the adjacent fault segment and foster earthquakes at shallow depths. |
| GEOSCAN ID | 329018 |
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