The Geological Susceptibility of Induced Earthquakes in the Duvernay Play

Abstract

Presently, consensus on the incorporation of induced earthquakes into seismic hazard has yet to be established. For example, the nonstationary, spatiotemporal nature of induced earthquakes is not well understood. Specific to the Western Canada Sedimentary Basin, geological bias in seismogenic activation potential has been suggested to control the spatial distribution of induced earthquakes regionally. In this paper, we train a machine learning algorithm to systemically evaluate tectonic, geomechanical, and hydrological proxies suspected to control induced seismicity. Feature importance suggests that proximity to basement, in situ stress, proximity to fossil reef margins, lithium concentration, and rate of natural seismicity are among the strongest model predictors. Our derived seismogenic potential map faithfully reproduces the current distribution of induced seismicity and is suggestive of other regions which may be prone to induced earthquakes. The refinement of induced seismicity geological susceptibility may become an important technique to identify significant underlying geological features and address induced seismic hazard forecasting issues.

Faults and associated karst collapse suggest conduits for fluid flow that influence hydraulic fracturing-induced seismicity

“…5). While we recognize this assertion is hardly definitive for this case, it supports an established idea that geological factors influence the likelihood of encountering induced earthquakes (62,(64)(65)(66)(67)(68)(69)(70). For example, HF operations susceptible to induced seismicity in the Duvernay play display a statistically significant spatial correspondence to the margins of a fossil reef (65).…”

“…These considerations are anecdotally supported by north-south strike-slip earthquakes (8,9) and evidence of a transtensional flower structure (68,73), a structure known to be conducive to vertical fluid flow (72). In this light, considering any features recognized during the reflection-seismic survey, wire-line log mapping, and drill core analysis that are indicative of these processes could provide cost-effective insight to the geological susceptibility for these types of earthquakes (69).…”

Hydraulic Fracture Injection Strategy Influences the Probability of Earthquakes in the Eagle Ford Shale Play of South Texas

“…We noted that ~10% of the HF wells in our eight focus regions targeted the Austin Chalk Formation (265 wells) rather than the Eagle Ford Formation (2,229 wells) where a lower percentage of wells correlated with seismicity (7.1% vs. 19.2%, supporting information, Table S2). The difference in earthquake probability appears to be a result of the geographic distribution of HF wells as the Austin Chalk is only targeted in a narrow zone where the seismicity was located (supporting information, Figure S7), supporting the widely held notion that proximity to susceptible faults is a critical factor for induced seismicity (e.g., Moeck et al, ; Pawley et al, ; Skoumal, Brudzinski, et al, ; Westwood et al, ). Although the lack of sufficient earthquake depth resolution prevents interpretation of where the seismicity is occurring, we note that carbonates like the Austin Chalk are more likely to produce induced seismicity than shales like the Eagle Ford (e.g., De Pater & Baisch, ; Lei et al, ; Sone & Zoback, ).…”

“…The potential for these larger magnitude events to cause damage underscores the need to understand the causes of induced seismicity and influences of different operational strategies. Recent work has suggested that proximity of operations to seismogenic faults and the orientation of those faults in the regional stress field are key factors, but not all induced seismicity has occurred on optimally oriented faults (e.g., Haffener et al, ; Hennings et al, ; Pawley et al, ; Skoumal, Brudzinski, et al, , ; Walsh & Zoback, ).…”

Hydraulic Fracturing‐Induced Seismicity

“…In some areas that are undergoing rapid development, the Duvernay is overpressured (i.e., pore pressure significantly above hydrostatic), and there is evidence to suggest that the susceptibility to induced seismicity is greater in overpressured zones (Eaton & Schultz, 2018). A recent analysis using machine learning methods indicates that proximity of the injection zone to basement, in situ stress, formation overpressure, proximity to fossil reef margins, lithium concentration (indicative of basement fluids and therefore fault conduits), and rate of natural seismicity are among the strongest predictors of geological susceptibility to induced seismicity in the Duvernay play (Pawley et al, 2018; Schultz & Pawley, 2019).…”