Stress Perturbation From Aseismic Slip Drives the Seismic Front During Fluid Injection in a Permeable Fault

2020 ◽  
Vol 125 (7) ◽  
Author(s):  
Nicolas Wynants‐Morel ◽  
Frédéric Cappa ◽  
Louis De Barros ◽  
Jean‐Paul Ampuero
Keyword(s):  
Fluid Injection ◽  
Aseismic Slip

Fluid-induced aseismic fault slip outpaces pore-fluid migration

Science ◽  
2019 ◽  
Vol 364 (6439) ◽  
pp. 464-468 ◽  
Author(s):  
Pathikrit Bhattacharya ◽  
Robert C. Viesca
Keyword(s):  
Pore Fluid ◽  
Fluid Injection ◽  
Fluid Migration ◽  
Aseismic Slip ◽  
Earthquake Triggering ◽  
Effective Normal Stress ◽  
Shear Rupture ◽  
Stress Changes ◽  
Slip History ◽  
Rupture Model

Earthquake swarms attributed to subsurface fluid injection are usually assumed to occur on faults destabilized by increased pore-fluid pressures. However, fluid injection could also activate aseismic slip, which might outpace pore-fluid migration and transmit earthquake-triggering stress changes beyond the fluid-pressurized region. We tested this theoretical prediction against data derived from fluid-injection experiments that activated and measured slow, aseismic slip on preexisting, shallow faults. We found that the pore pressure and slip history imply a fault whose strength is the product of a slip-weakening friction coefficient and the local effective normal stress. Using a coupled shear-rupture model, we derived constraints on the hydromechanical parameters of the actively deforming fault. The inferred aseismic rupture front propagates faster and to larger distances than the diffusion of pressurized pore fluid.

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 Stabilization of fault slip by fluid injection in the laboratory and in situ

2019 ◽  
Vol 5 (3) ◽  
pp. eaau4065 ◽  
Author(s):  
Frédéric Cappa ◽  
Marco Maria Scuderi ◽  
Cristiano Collettini ◽  
Yves Guglielmi ◽  
Jean-Philippe Avouac
Keyword(s):  
Fluid Flow ◽  
Fluid Pressure ◽  
Fault Slip ◽  
Fluid Injection ◽  
Aseismic Slip ◽  
Fault Creep ◽  
Frictional Properties

Faults can slip seismically or aseismically depending on their hydromechanical properties, which can be measured in the laboratory. Here, we demonstrate that fault slip induced by fluid injection in a natural fault at the decametric scale is quantitatively consistent with fault slip and frictional properties measured in the laboratory. The increase in fluid pressure first induces accelerating aseismic creep and fault opening. As the fluid pressure increases further, friction becomes mainly rate strengthening, favoring aseismic slip. Our study reveals how coupling between fault slip and fluid flow promotes stable fault creep during fluid injection. Seismicity is most probably triggered indirectly by the fluid injection due to loading of nonpressurized fault patches by aseismic creep.

Seismicity triggered by fluid injection-induced aseismic slip

Science ◽  
2015 ◽  
Vol 348 (6240) ◽  
pp. 1224-1226 ◽  
Author(s):  
Y. Guglielmi ◽  
F. Cappa ◽  
J.-P. Avouac ◽  
P. Henry ◽  
D. Elsworth
Keyword(s):  
Fluid Injection ◽  
Aseismic Slip

Fluid-injection induced earthquakes characterized by hybrid-frequency waveforms manifest the transition from aseismic to seismic slip

2020 ◽  
Author(s):  
Hongyu Yu ◽  
Rebecca Harrington ◽  
Honn Kao ◽  
Yajing Liu ◽  
Bei Wang
Keyword(s):  
Plate Boundary ◽  
Low Frequency ◽  
Seismic Signal ◽  
Fluid Injection ◽  
Aseismic Slip ◽  
Induced Earthquakes ◽  
Seismic Slip ◽  
Hybrid Frequency ◽  
New Type ◽  
Lower Corner

Abstract Aseismic slip loading has recently been proposed as a complementary mechanism for moderate earthquakes (M3+) induced over the short operational period of hydraulic fracturing stimulations but located several kilometers away from the wellbore. However, aseismic/slow slip signals linked to fluid injection-induced earthquakes remain largely undocumented to date. Here we report a new type of induced seismic signal consisting of an impulsive broadband onset followed by protracted low-frequency ringing. Earthquakes characterized by hybrid-frequency waveforms (EHWs) differ from ordinary induced earthquakes by having broader P and S-pulses (implying longer source durations) and lower corner frequencies (implying either slower rupture speeds, lower stress drop values, or a combination of both). The characteristics described above are identical to low-frequency earthquakes found in plate boundary zones. EHWs could thus manifest the source process that bridges the slow (aseismic) slip inferred by recent modeling and observations near the wellbore to seismic slip at greater distances.

scholarly journals Three-dimensional aseismic ruptures driven by fluid injection

2021 ◽  
Author(s):  
Alexis Sáez ◽  
Brice Lecampion ◽  
Pathikrit Bhattacharya ◽  
Robert C. Viesca
Keyword(s):  
Analytical Solution ◽  
Pore Pressure ◽  
Induced Seismicity ◽  
Amplification Factor ◽  
Three Dimensional ◽  
Fluid Injection ◽  
Seismic Events ◽  
Aseismic Slip ◽  
Rupture Area ◽  
Self Similar

<div> <div> <div> <p>Injection-induced seismicity is usually observed as an enlarging cloud of seismic events that grows in a diffusive manner around the injection zone. These observations are commonly interpreted as the triggering of instabilities in pre-existing fractures and faults due to the direct effect of pore pressure increase (Shapiro, 2015), whereas poroelastic stressing is usually associated with the occurrence of seismic events beyond the plausible zone affected by pore pressure diffusion (Segall and Lu, 2015). However, an alternative triggering mechanism based on the elastic transfer of stress due to injection- induced aseismic slip has been recently proposed (Viesca, 2015; Guglielmi et al, 2015). Previous studies have shown that in critically stressed faults, the aseismic rupture front can outpace fluid diffusion (Garagash and Germanovich, 2012; Bhattacharya and Viesca, 2019), and in turn be the primary cause that controls the evolution of seismicity as it has been recently inferred from in-situ experiments of fluid injection (Duboeuf et al., 2017) and recent cases of injection-induced earthquakes (Eyre et al, 2019).</p> <div> <div> <div> <p>Despite the great relevance of aseismic slip on injection-induced seismicity, the conditions that control the three-dimensional propagation of aseismic ruptures are still poorly constrained. This is in part due to the challenge of solving such a 3D moving boundary problem in which both fault slip and rupture shape are unknown. Here, we study the mechanics of injection-induced aseismic ruptures on a planar fault characterized by a strength equal to the product of a constant friction coefficient and the effective normal stress. We systematically track the temporal evolution of the rupture area relative to the evolution of the pressurized zone and focus on the effect of the initial stress state and injection scenario. For injection at constant flux, we derive a semi-analytical solution for circular ruptures (for a Poisson’s ratio equal to zero), which gives the ratio between the rupture radius and a nominal pore pressure front location, which we named as amplification factor λ. This amplification factor is a function of a unique dimensionless parameter that depends on the initial fault stress criticality and the fluid-induced overpressure. Then, we generalize the semi-analytical solution to the case of non-circular ruptures (for any value of the Poisson’s ratio) by solving numerically for the spatiotemporal evolution of fault slip using a fully implicit boundary-element-based solver with quadratic triangular elements. We show that the rupture front is nearly elliptical and the rupture area A<sub>r</sub> evolves in a self-similar diffusive manner such that A<sub>r</sub>(t) = 4παλ<sup>2</sup>t, where α is the fault hydraulic diffusivity and λ is the amplification factor for circular ruptures. The rupture area is greater than the nominal pressurized area if λ > 1. The semi-analytical solution for the rupture area provides a unique opportunity for verifying numerical hydro-mechanical solvers. After, we investigate numerically the case of circular and non-circular ruptures driven by injection at constant pressure instead of constant flux. We show that the self-similar property of the rupture growth is lost under this injection scenario.</p> </div> </div> </div> </div> </div> </div>

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>

A new approach to the hydraulic fracture geometric dimensions determination

2017 ◽  
Vol 12 (1) ◽  
pp. 126-134
Author(s):  
A.M. Ilyasov
Keyword(s):  
Exact Solution ◽  
Hydraulic Fracture ◽  
Pressure Gauge ◽  
Hyperbolic Type ◽  
Fluid Injection ◽  
Fracturing Fluid ◽  
New Approach ◽  
Gauge Data ◽  
Bottomhole Pressure ◽  
Half Length

Based on the generalized Perkins-Kern-Nordgren model (PKN) for the development of a hyperbolic type vertical hydraulic fracture, an exact solution is obtained for the hydraulic fracture self-oscillations after terminating the fracturing fluid injection. These oscillations are excited by a rarefaction wave that occurs after the injection is stopped. The obtained solution was used to estimate the height, width and half-length of the hydraulic fracture at the time of stopping the hydraulic fracturing fluid injection based on the bottomhole pressure gauge data.

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