Stress Transfer From Opening Hydraulic Fractures Controls the Distribution of Induced Seismicity

Abstract

Understanding the dominant physical processes that cause fault reactivation due to fluid injection is vital to develop strategies to avoid and mitigate injection-induced seismicity. Injection-induced seismicity is a risk for several industries, including hydraulic fracturing, geothermal stimulation, oilfield waste disposal and carbon capture and storage, with hydraulic fracturing having been associated with some of the highest magnitude induced earthquakes (M > 5). As such, strict regulatory schemes have been implemented globally to limit the felt seismicity associated with operations. In the UK, a very strict "traffic light" system is currently in place. These procedures were employed several times during injection at the PNR-1z well at Preston New Road, Lancashire, UK, from October to December 2018. As injection proceeded, it became apparent to the operator that stages were interacting with a seismogenic planar structure, interpreted as a fault zone, with several M L > 0.5 events occurring. Microseismicity was clustered along this planar structure in a fashion that could not readily be explained through pore pressure diffusion or hydraulic fracture growth. Instead, we investigate the role of static elastic stress transfer created by the tensile opening of hydraulic fractures. We find that the spatial distributions of microseismicity are strongly correlated with areas that receive positive Mohr-Coulomb stress changes from the tensile fracture opening, while areas that receive negative Mohr-Coulomb stress change are quiescent. We conclude that the stressing due to tensile hydraulic fracture opening plays a significant role in controlling the spatiotemporal distribution of induced seismicity.

Hydraulic Fracturing‐Induced Seismicity

“…In this sense, the temporal evolution of earthquake swarms does not tend to follow traditional fore/main/aftershock patterns (Hill, 1977; Mogi, 1967). This swarm‐like character is in accord with closer assessments of HF‐induced earthquakes, where interevent times follow a nonhomogeneous Poisson distribution (Hajati et al, 2015) with smaller contributions from earthquake interactions (Catalli et al, 2016; Kettlety et al, 2019; Maghsoudi et al, 2018). This is not surprising, as stage‐by‐stage stimulation can sequentially illuminate faults.…”

“…Admittedly, these observations are often obscured because of the narrowing gap in between stage simulations from increasingly fast completion pacing and styles (e.g., zipper fracks). However, there are noteworthy cases during the initial development of HF where simpler and slower completions caused earthquakes (Friberg et al, 2014; Kettlety et al, 2019). For example, in December of 2011 near Cardston, Alberta (Schultz, Mei, et al, 2015) a single‐well pad was completed with ~24 hr between stages.…”

“…Similar results can also be noted in more complex HF completions, where sufficiently close monitoring is available (Clarke et al, 2019; Eaton et al, 2018; Yu et al, 2019). In these cases, there tends to be clear and nearly immediate response (a few hours) between stage stimulation and resultant earthquakes (Kettlety et al, 2019; Kwiatek et al, 2019). As well, there is often a proximal association between these seismogenic stages and illuminated faults.…”

Statistical Modeling and Characterization of Induced Seismicity Within the Western Canada Sedimentary Basin

“…For example, the large wastewater disposal‐induced events in Oklahoma triggered typical aftershock behavior (Keranen et al, 2014; McGarr & Barbour, 2017), while the HF‐induced clustering near Youngstown, Ohio, and injection‐related events in central Arkansas, near Guy and Greenbrier, displayed swarm‐like characteristics (Horton, 2012; Llenos & Michael, 2013; Skoumal et al, 2015). Studies have shown that both natural and anthropogenic changes to the subsurface fluid content can enhance or induce clustered earthquake sequences via subsidence and changes in Coulomb fault stress or pore pressure conditions, especially near critically oriented structures (Bao & Eaton, 2016; Brodsky & Lajoie, 2013; Goebel et al, 2015; Keranen et al, 2014; Kettlety et al, 2019, 2020; Kumazawa & Ogata, 2013; Langenbruch & Shapiro, 2010; Schoenball et al, 2015; Segall, 1985). The nature of clustering observed within a region may be attributed to its rheological structure, in the framework of viscoelastic deformation (Ben‐Zion & Lyakhovsky, 2006).…”

A novel approach to assessing nuisance risk from seismicity induced by UK shale gas development, with implications for future policy design

“…Awareness and concern regarding the impacts of seismicity induced by hydraulic fracturing have grown significantly in recent years (e.g Ellsworth, 2013;Davies et al, 2013;Cotton et al, 2014;Whitmarsh et al, 2015;Williams et al, 2017;Atkinson et al, 2020), which may pose a threat to the future development of unconventional gas resources (Kraft et al, 2009). There is evidence that tolerance of such operations will be increased if the public is made aware of the potential consequences of the resulting ground shaking (Giardini, 2009;Bommer et al, 2015).…”