scholarly journals The role of aseismic slip in hydraulic fracturing–induced seismicity

2019 ◽  
Vol 5 (8) ◽  
pp. eaav7172 ◽  
Author(s):  
Thomas S. Eyre ◽  
David W. Eaton ◽  
Dmitry I. Garagash ◽  
Megan Zecevic ◽  
Marco Venieri ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Slip Rate ◽  
Aseismic Slip ◽  
Dynamic Rupture ◽  
Induced Earthquakes ◽  
Rock Composition ◽  
Injection Zone ◽  
In Situ Experiments ◽  
Stress Changes

Models for hydraulic fracturing–induced earthquakes in shales typically ascribe fault activation to elevated pore pressure or increased shear stress; however, these mechanisms are incompatible with experiments and rate-state frictional models, which predict stable sliding (aseismic slip) on faults that penetrate rocks with high clay or total organic carbon. Recent studies further indicate that the earthquakes tend to nucleate over relatively short injection time scales and sufficiently far from the injection zone that triggering by either poroelastic stress changes or pore pressure diffusion is unlikely. Here, we invoke an alternative model based on recent laboratory and in situ experiments, wherein distal, unstable regions of a fault are progressively loaded by aseismic slip on proximal, stable regions stimulated by hydraulic fracturing. This model predicts that dynamic rupture initiates when the creep front impinges on a fault region where rock composition favors dynamic and slip rate weakening behavior.

Coupling poroelastic stress change and rate-state fault slip models to simulate fluid injection induced seismic and aseismic slip

2020 ◽  
Author(s):  
Yajing Liu ◽  
Alessandro Verdecchia ◽  
Kai Deng ◽  
Rebecca Harrington
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Fault Slip ◽  
Stress Change ◽  
Fluid Injection ◽  
Coulomb Stress ◽  
Aseismic Slip ◽  
Injection Wells ◽  
Wastewater Disposal ◽  
Stress Changes

<p>Fluid injection in unconventional hydrocarbon resource exploration can introduce poroelastic stress and pore pressure changes, which in some cases may lead to aseismic slip on pre-existing fractures or faults. All three processes have been proposed as candidates for inducing earthquakes up to 10s of kilometers from injection wells. In this study, we examine their relative roles in triggering fault slip under both wastewater disposal and hydraulic fracturing scenarios. We first present modeling results of poroelastic stress changes on a previously unmapped fault near Cushing, Oklahoma, due to injection at multiple wastewater disposal wells within ~ 10 km of distance, where over 100 small to moderate earthquakes were reported between 2015/09 to 2016/11 including a Mw5.0 event at the end of the sequence. Despite the much larger amplitude of pore pressure change, we find that earthquake hypocenters are well correlated with positive shear stress change, which dominates the regimes of positive Coulomb stress change encouraging failure. Depending on the relative location of the disposal well to the recipient fault and its sense of motion, fluid injection can introduce either positive or negative Coulomb stress changes, therefore promoting or inhibiting seismicity. Our results suggest that interaction between multiple injection wells needs to be considered in induced seismicity hazard assessment, particularly for areas of dense well distributions. Next, we plan to apply the model to simulate poroelastic stress changes due to multi-stage hydraulic fracturing wells near Dawson Creek, British Columbia, where a dense local broadband seismic array has been in operation since 2016. We will investigate the relative amplitudes, time scales, and spatial ranges of pore pressure versus solid matrix stress changes in influencing local seismicity.</p><p>Finally, we have developed a rate-state friction framework for calculating slip on a pre-existing fault under stress perturbations for both the disposal and hydraulic fracturing cases. Preliminary fault slip simulation results suggest that fault response (aseismic versus seismic) highly depends on 1) the relative timing in the intrinsic earthquake cycle (under tectonic loading) when the stress perturbation is introduced, 2) the amplitude of the perturbation relative to the background fault stress state, and 3) the duration of the perturbation relative to the “memory” timescale governed by the rate-state properties of the fault. Our modeling results suggest the design of injection parameters could be critical for preventing the onset of seismic slip.</p>

scholarly journals Rupture-dependent breakdown energy in fault models with thermo-hydro-mechanical processes

2020 ◽  
Author(s):  
Valère Lambert ◽  
Nadia Lapusta
Keyword(s):  
Material Property ◽  
Numerical Models ◽  
Slip Rate ◽  
Shear Cracks ◽  
Dynamic Rupture ◽  
Rupture Dynamics ◽  
Stress Changes ◽  
History Of ◽  
Thermal Pressurization ◽  
Pass Through

Abstract. Substantial insight into earthquake source processes has resulted from considering frictional ruptures analogous to cohesive-zone shear cracks from fracture mechanics. This analogy holds for slip-weakening representations of fault friction that encapsulate the resistance to rupture propagation in the form of breakdown energy, analogous to fracture energy, prescribed in advance as if it were a material property of the fault interface. Here, we use numerical models of earthquake sequences with enhanced weakening due to thermal pressurization of pore fluids to show how accounting for thermo-hydro-mechanical processes during dynamic shear ruptures makes breakdown energy rupture-dependent. We find that local breakdown energy is neither a constant material property nor uniquely defined by the amount of slip attained during rupture, but depends on how that slip is achieved through the history of slip rate and dynamic stress changes during the rupture process. As a consequence, the frictional breakdown energy of the same location along the fault can vary significantly in different earthquake ruptures that pass through. These results suggest the need for re-examining the assumption of pre-determined frictional breakdown energy common in dynamic rupture modeling and for better understanding of the factors that control rupture dynamics in the presence of thermo-hydro-mechanical processes.

Comprehensive Characterization and Mitigation of Hydraulic Fracturing-Induced Seismicity in Fox Creek, Alberta

SPE Journal ◽  
2021 ◽  
pp. 1-12
Author(s):  
Gang Hui ◽  
Shengnan Chen ◽  
Zhangxin Chen ◽  
Fei Gu ◽  
Mathab Ghoroori ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Hydraulic Fracture ◽  
Induced Seismicity ◽  
Mitigation Strategy ◽  
Moment Magnitude ◽  
Induced Earthquakes ◽  
Data Set ◽  
Comprehensive Characterization

Summary The relationships among formation properties, fracturing operations, and induced earthquakes nucleated at distinctive moments and positions remain unclear. In this study, a complete data set on formations, seismicity, and fracturing treatments is collected in Fox Creek, Alberta, Canada. The data set is then used to characterize the induced seismicity and evaluate its susceptibility toward fracturing stimulations via integration of geology, geomechanics, and hydrology. Five mechanisms are identified to account for spatiotemporal activation of the nearby faults in Fox Creek, where all major events [with a moment magnitude (Mw) greater than 2.5] are caused by the increase in pore pressure and poroelastic stress during the fracturing operation. In addition, an integrated geological index (IGI) and a combined geomechanical index (CGI) are first proposed to indicate seismicity susceptibility, which is consistent with the spatial distribution of induced earthquakes. Finally, mitigation strategy results suggest that enlarging a hydraulic fracture-fault distance and decreasing a fracturing job size can reduce the risk of potential seismic activities.

Induced seismicity associated with fluid injection into a fractured rock mass

2020 ◽  
Author(s):  
Brice Lecampion ◽  
Federico Ciardo ◽  
Alexis Saèz Uribe ◽  
Andreas Möri
Keyword(s):  
Rock Mass ◽  
Percolation Threshold ◽  
Pore Pressure ◽  
Finite Volume ◽  
Fractured Rock ◽  
Fluid Injection ◽  
Aseismic Slip ◽  
Dynamic Rupture ◽  
Fractured Rock Mass

<p>We investigate via numerical modeling the growth of an aseismic rupture and the possible nucleation of a dynamic rupture driven by fluid injection into a fractured rock mass. We restrict to the case of highly transmissive fractures compared to the rock matrix at the scale of the injection duration and thus assume an impermeable matrix. We present a new 2D hydro-mechanical solver allowing to treat a large number of pre-existing frictional discontinuities. The quasi-static (or quasi-dynamic) balance of momentum is discretized using boundary elements while fluid flow inside the fracture is discretized via finite volume. A fully implicit scheme is used for time integration. Combining a hierarchical matrix approximation of the original boundary element matrix with a specifically developed block pre-conditioner enable a robust and efficient solution of large problems (with up to 10<sup>6</sup> unknowns). In order to treat accurately fractures intersections, we use piece-wise linear displacement discontinuities element for elasticity and a vertex centered finite volume method for flow.</p><p>We first consider the case of a randomly oriented discrete fracture network (DFN) having friction neutral properties. We discuss the very different behavior associated with marginally pressurized versus critically stressed conditions. As an extension of the case of a planar fault (Bhattacharya and Viesca, Science, 2019), the injection into a DFN problem is governed by the distribution (directly associated with fracture orientation) of a dimensionless parameter combining the local stress criticality (function of the in-situ principal effective stress, friction coefficient and local fracture orientation) and the normalized injection over-pressure. The percolation threshold of the DFN which characterizes the hydraulic connectivity of the network plays an additional role in fluid driven shear cracks growth. Our numerical simulations show that a critically stressed DFN exhibits fast aseismic slip growth (much faster than the fluid pore-pressure disturbance front propagation) regardless of the DFN percolation threshold. This is because the slipping patch growth is driven by the cascades of shear activation due to stress interactions as fractures get activated. On the other hand, the scenario is different for marginally pressurized / weakly critically stressed DFN. The aseismic slip propagation is then tracking pore pressure diffusion inside the DFN. As a result, the DFN percolation threshold plays an important role with low percolation leading to fluid localization and thus restricted aseismic rupture growth.</p><p>We then discuss the case of fluid injection into a fault damage zone. Using a linear frictional weakening model for the fault, we investigate the scenario of the nucleation of a dynamic rupture occurring after the end of the injection (as observed in several instances in the field). We delimit the injection and in-situ conditions supporting such a possibility.</p>

scholarly journals Pore-pressure diffusion, enhanced by poroelastic stresses, controls induced seismicity in Oklahoma

2019 ◽  
Vol 116 (33) ◽  
pp. 16228-16233 ◽  
Author(s):  
Guang Zhai ◽  
Manoochehr Shirzaei ◽  
Michael Manga ◽  
Xiaowei Chen
Keyword(s):  
Pore Pressure ◽  
Induced Seismicity ◽  
Energy Demand ◽  
Regional Scale ◽  
Exceedance Probability ◽  
Resource Exploitation ◽  
Induced Earthquakes ◽  
Seismicity Rate ◽  
Pressure Diffusion ◽  
Stress Changes

Induced seismicity linked to geothermal resource exploitation, hydraulic fracturing, and wastewater disposal is evolving into a global issue because of the increasing energy demand. Moderate to large induced earthquakes, causing widespread hazards, are often related to fluid injection into deep permeable formations that are hydraulically connected to the underlying crystalline basement. Using injection data combined with a physics-based linear poroelastic model and rate-and-state friction law, we compute the changes in crustal stress and seismicity rate in Oklahoma. This model can be used to assess earthquake potential on specific fault segments. The regional magnitude–time distribution of the observed magnitude (M) 3+ earthquakes during 2008–2017 is reproducible and is the same for the 2 optimal, conjugate fault orientations suggested for Oklahoma. At the regional scale, the timing of predicted seismicity rate, as opposed to its pattern and amplitude, is insensitive to hydrogeological and nucleation parameters in Oklahoma. Poroelastic stress changes alone have a small effect on the seismic hazard. However, their addition to pore-pressure changes can increase the seismicity rate by 6-fold and 2-fold for central and western Oklahoma, respectively. The injection-rate reduction in 2016 mitigates the exceedance probability of M5.0 by 22% in western Oklahoma, while that of central Oklahoma remains unchanged. A hypothetical injection shut-in in April 2017 causes the earthquake probability to approach its background level by ∼2025. We conclude that stress perturbation on prestressed faults due to pore-pressure diffusion, enhanced by poroelastic effects, is the primary driver of the induced earthquakes in Oklahoma.

scholarly journals Rupture-dependent breakdown energy in fault models with thermo-hydro-mechanical processes

Solid Earth ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 2283-2302
Author(s):  
Valère Lambert ◽  
Nadia Lapusta
Keyword(s):  
Material Property ◽  
Numerical Models ◽  
Slip Rate ◽  
Shear Cracks ◽  
Dynamic Rupture ◽  
Rupture Dynamics ◽  
Stress Changes ◽  
History Of ◽  
Thermal Pressurization ◽  
Pass Through

Abstract. Substantial insight into earthquake source processes has resulted from considering frictional ruptures analogous to cohesive-zone shear cracks from fracture mechanics. This analogy holds for slip-weakening representations of fault friction that encapsulate the resistance to rupture propagation in the form of breakdown energy, analogous to fracture energy, prescribed in advance as if it were a material property of the fault interface. Here, we use numerical models of earthquake sequences with enhanced weakening due to thermal pressurization of pore fluids to show how accounting for thermo-hydro-mechanical processes during dynamic shear ruptures makes breakdown energy rupture-dependent. We find that local breakdown energy is neither a constant material property nor uniquely defined by the amount of slip attained during rupture, but depends on how that slip is achieved through the history of slip rate and dynamic stress changes during the rupture process. As a consequence, the frictional breakdown energy of the same location along the fault can vary significantly in different earthquake ruptures that pass through. These results suggest the need to reexamine the assumption of predetermined frictional breakdown energy common in dynamic rupture modeling and to better understand the factors that control rupture dynamics in the presence of thermo-hydro-mechanical processes.

A Long-Lived Swarm of Hydraulic Fracturing-Induced Seismicity Provides Evidence for Aseismic Slip

2020 ◽  
Vol 110 (5) ◽  
pp. 2205-2215 ◽  
Author(s):  
Thomas S. Eyre ◽  
Megan Zecevic ◽  
Rebecca O. Salvage ◽  
David W. Eaton
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Induced Seismicity ◽  
Aftershock Sequence ◽  
Fluid Migration ◽  
Aseismic Slip ◽  
Seismicity Rate ◽  
Slow Earthquakes ◽  
Seismic Swarms ◽  
Event Distribution

ABSTRACT Seismic swarms are defined as an increase in seismicity that does not show a clear mainshock–aftershock sequence. Typically, swarms are primarily associated with either fluid migration or slow earthquakes (aseismic slip). In this study, we analyze a swarm induced by hydraulic fracturing (HF) that persisted for an unusually long duration of more than 10 months. Swarms ascribed to fluid injection are usually characterized by an expanding seismicity front; in this case, however, characteristics such as a relatively steady seismicity rate over time and lack of hypocenter migration cannot be readily explained by a fluid-diffusion model. Here, we show that a different model for HF-induced seismicity, wherein an unstable region of a fault is loaded by proximal, pore-pressure-driven aseismic slip, better explains our observations. According to this model, the steady seismicity rate can be explained by a steady slip velocity, while the spatial stationarity of the event distribution is due to lateral confinement of the creeping region of the fault with increased pore pressure. Our results may have important implications for other induced or natural seismic swarms, which could be similarly explained by aseismic loading of asperities driven by fluid overpressure rather than the often-attributed fluid-migration model.

scholarly journals Earthquakes Influenced by Water

2021 ◽  
pp. 61-82
Author(s):  
Chi-Yuen Wang ◽  
Michael Manga
Keyword(s):  
Pore Pressure ◽  
Human Activities ◽  
Seismic Events ◽  
Relative Importance ◽  
Induced Earthquakes ◽  
Surface Loading ◽  
Stress Changes ◽  
The Future ◽  
Subsurface Engineering ◽  
Pressure Changes

AbstractInjecting fluids in the crust, or their extraction, changes pore pressure and poroelastic stresses. Both pressure and stress changes can promote seismicity and, hence, the seismic events are called induced earthquakes. The filling of reservoirs on Earth’s surface can also induce earthquakes from some combination of surface loading and pore pressure changes. Attribution of any given earthquake to human activities, however, is not always straightforward. There remains debate about what controls the magnitude of induced earthquakes, the relative importance of pore pressure changes and poroelastic stresses, and how to best manage injection and extraction to minimize seismicity. As the scale and distribution of subsurface engineering expand globally, we should expect more and larger induced earthquakes in the future.

scholarly journals Increased likelihood of induced seismicity in highly overpressured shale formations

2018 ◽  
Vol 214 (1) ◽  
pp. 751-757 ◽  
Author(s):  
David W Eaton ◽  
Ryan Schultz
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Induced Earthquakes ◽  
Shale Formations ◽  
Western Canada Sedimentary Basin ◽  
Natural Processes ◽  
Negligible Probability ◽  
Pore Pressure Gradient ◽  
Geological Timescale

SUMMARY Fluid-injection processes such as disposal of saltwater or hydraulic fracturing can induce earthquakes by increasing pore pressure and/or shear stress on faults. Natural processes, including transformation of organic material (kerogen) into hydrocarbon and cracking to produce gas, can similarly cause fluid overpressure. Here, we document two examples from the Western Canada Sedimentary Basin where earthquakes induced by hydraulic fracturing are strongly clustered within areas characterized by pore-pressure gradient in excess of 15 kPa m−1. Despite extensive hydraulic-fracturing activity associated with resource development, induced earthquakes are virtually absent in the Montney and Duvernay Formations elsewhere. Statistical analysis suggests a negligible probability that this spatial correlation developed by chance. This implies that, in addition to known factors such as anthropogenic pore-pressure increase and proximity to critically stressed faults, high in situ overpressure of shale formations may also represent a controlling factor for inducing earthquakes by hydraulic fracturing. On a geological timescale, natural pore-pressure generation may lead to fault-slip episodes that regulate the magnitude of formation overpressure.

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