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TitleComplex 3D migration and delayed triggering of hydraulic fracturing-induced seismicity: A case study near Fox Creek, Alberta
AuthorGao, D; Kao, HORCID logo; Wang, BORCID logo; Visser, R; Schultz, RORCID logo; Harrington, RORCID logo
SourceGeophysical Research Letters 2022 p. 1-12, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20210217
Mediapaper; digital; on-line
File formatpdf
NTS83K/06; 83K/07; 83K/10; 83K/11
Lat/Long WENS-117.5000 -116.5000 54.7500 54.2500
Subjectshydrogeology; earthquakes; hydraulic fracturing; porosity; faults; pore pressures
Illustrationslocation maps; histograms; cross-sections; models
ProgramEnvironmental Geoscience Shale Gas - induced seismicity
Released2022 01 21
AbstractEarthquakes resulting from hydraulic fracturing (HF) can have delayed triggering relative to injection commencement over a varied range of time scales, with the majority of M >= 4 mainshocks occurring near/after well completion. This poses serious challenges for risk mitigation and hazard assessment. Here, we document a high-resolution, three-dimensional source migration process with delayed mainshock triggering that is controlled by local hydrogeological conditions near Fox Creek, Alberta, Canada. Our results reveal that poroelastic effects might contribute to induced seismicity, but are probably insufficient to activate a large fault segment not critically stressed. The rapid pore-pressure build-up from HF can be very localized and capable of producing large, felt earthquakes if adequate hydrological paths exist. We interpret the delayed triggering as a manifestation of pore-pressure build-up along pre-existing faults needed to facilitate seismic failure. Our findings can explain why so few injection operations are seismogenic.
Summary(Plain Language Summary, not published)
Fluid injection-induced earthquakes (IIE), especially the mainshocks, are often observed to occur near or after well completion. Such delayed triggering relative to injection commencement poses serious challenges for both regulators and the energy industry to establish an effective mitigation strategy for the potential seismic risk. In this study, we reveal a high-resolution, complex three-dimensional pattern of IIE migration in Fox Creek, Alberta, Canada. The observed first-outward-then-inward IIE sequence highlights the significance of hydrogeological networks in facilitating fluid pressure migration and the associated seismic failure. The detailed spatiotemporal distribution of IIE suggests that the effect of pore-pressure build-up from hydraulic fracturing (HF) can be very localized. The delayed triggering is a combined result from the fluid pressure migration and the current stress state of the hosting fault system away from the HF wells. The findings from this study also provide plausible explanations on why only a very limited number of fluid injections are seismogenic.

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