Nucleation of dynamic slip on a hydraulically fractured fault

Azad, Mohammad; Garagash, Dmitry I.; Satish, Mysore G.

doi:10.1002/2016jb013835

Cited by 23 publications

(32 citation statements)

References 74 publications

(138 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Poiseuille law

normalΨ = - \frac{1}{ε} {(ω_{n} + ω_{h})}^{3} \frac{∂Π}{\partial ξ}

where

ε = \frac{Q_{0} μ^{'} E^{'}}{2 τ_{p}^{2} u_{w}^{2}}

is called the hydraulic fracture loading factor since it is proportional to the product of Q 0 and μ ′ . A similar definition can be found in Azad et al ().…”

Section: The Modelmentioning

confidence: 98%

“…Scaling is useful to simplify the above governing equations together with initial and boundary conditions (Barenblatt, ). Following Garagash and Germanovich () and Azad et al (), we introduce the following five characteristic scaling parameters

ℓ_{*} = \frac{E^{'}}{2 τ_{p}} u_{w}, t_{*} = \frac{μ^{'} {E^{'}}^{2}}{4 τ_{p}^{3}}, w_{*} = u_{w}, p_{*} = τ_{p}, q_{*} = Q_{0}

Hence, we define the dimensionless position and time as

ξ = x / ℓ_{*}, η = t / t_{*}

and the three moving fronts are defined as

φ_{o} = l_{o} / ℓ_{*}, φ_{s} = l_{s} / ℓ_{*}, φ_{f} = l_{f} / ℓ_{*}

…”

Section: The Modelmentioning

confidence: 99%

“…Comparisons with existing results: (a) normalized critical slip zone size φ sc versus normalized background shear stress (1 − Σ s ) at a dimensionless injection rate Q 0 / q w = 0.3, where q w is defined by Garagash and Germanovich (, referred to as G‐G [2012] in the plot) as

b_{0}^{2} σ_{0} / μ^{'} l_{*}

when the ambient pore pressure on the fault plane is zero and the unchanged permeability is determined by the preexisting hydraulic aperture. (b) Normalized slip zone size ahead of the hydraulic fracture (HF) tip versus normalized hydraulic fracture zone size for f d = 0 (Figure 5a in Azad et al, ) and f d = 0.4 (Figure 9a in Azad et al, ) at the fixed dimensionless hydraulic fracture loading factor (= 0.2) that is defined by equation 23 in Azad et al (). The Skempton's coefficient is zero for gas‐filled faults and unsaturated geothermal reservoirs assumed in this paper.…”

Section: Numerical Algorithm and Verificationmentioning

confidence: 99%

“…By using it, Garagash and Germanovich (2012) captured nucleation and then arrest of dynamic slip along a porous and very permeable fault. The combination of the linear slip-weakening friction law and pressure diffusion has also been used for simulating earthquakes (Yamashita & Suzuki, 2011), landslides (Viesca & Rice, 2012), and hydraulic fracture growth (Azad et al, 2017;Galis et al, 2017;Garagash & Germanovich, 2012;Zhang et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A Numerical Model for the Effect of Permeability Change on Faulting During Fluid Injection

Zhang

Jeffrey

2019

JGR Solid Earth

View full text Add to dashboard Cite

Slip and slip zone development during constant‐rate fluid injection into a permeable fault in an infinite, impermeable elastic rock is studied here numerically using a hydromechanical fracture model. The interplay of slip zone growth and fault dilatancy is assumed to be affected by linear slip weakening of frictional strength and slip‐induced dilation. The discretization error is minimized by using element sizes based on a mesh sensitivity study to obtain accurate slipping and pressurized lengths. Comparisons with published results for large and zero fault permeability cases demonstrate the validity of the numerical results. Dimensional analysis is used to identify five parameters that control slip development, including the slip‐induced dilatancy factor, initial fault permeability, the product of fluid viscosity and injection rate, the background shear to normal stress ratio, and the residual coefficient of friction. Conditions leading a quasi‐static stable slip to either continue as stable aseismic slip or accelerate are discussed. Acceleration of slip occurs on less permeable faults characterized by a hybrid tensile‐shear fracture subject to higher pressure, while prolonged aseismic slip occurs along a more permeable fault subject to lower pressure. During long‐duration aseismic slip the pressure varies slightly around the value that equalizes the fault shear strength and the background shear stress. A permeability perturbation in the form of a sinusoidal fault aperture distribution does not change the tendency of the slip to be slow and stable. Like preexisting permeability, slip‐induced dilation responses play a role in limiting pressure level and extending the slow slip period.

show abstract

“…Poiseuille law

normalΨ = - \frac{1}{ε} {(ω_{n} + ω_{h})}^{3} \frac{∂Π}{\partial ξ}

where

ε = \frac{Q_{0} μ^{'} E^{'}}{2 τ_{p}^{2} u_{w}^{2}}

is called the hydraulic fracture loading factor since it is proportional to the product of Q 0 and μ ′ . A similar definition can be found in Azad et al ().…”

Section: The Modelmentioning

confidence: 98%

ℓ_{*} = \frac{E^{'}}{2 τ_{p}} u_{w}, t_{*} = \frac{μ^{'} {E^{'}}^{2}}{4 τ_{p}^{3}}, w_{*} = u_{w}, p_{*} = τ_{p}, q_{*} = Q_{0}

Hence, we define the dimensionless position and time as

ξ = x / ℓ_{*}, η = t / t_{*}

and the three moving fronts are defined as

φ_{o} = l_{o} / ℓ_{*}, φ_{s} = l_{s} / ℓ_{*}, φ_{f} = l_{f} / ℓ_{*}

…”

Section: The Modelmentioning

confidence: 99%

b_{0}^{2} σ_{0} / μ^{'} l_{*}

Section: Numerical Algorithm and Verificationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A Numerical Model for the Effect of Permeability Change on Faulting During Fluid Injection

Zhang

Jeffrey

2019

JGR Solid Earth

View full text Add to dashboard Cite

show abstract

“…Quantification of the coupled fluid migration and shearing along permeable faults is thus recognized as critical for understanding injection‐induced seismicity and the potential for dynamic, unstable slip nucleation. The nucleation of dynamic slip from a constant permeability fault or a fault that is opened by the injected fluid has been investigated (Azad et al, ; Garagash & Germanovich, ; Viesca & Rice, ), revealing the importance of lower shear stress environments and a smaller opening zone on reducing the likelihood of unstable fault slip events. On the other hand, the permeability changes occurring during dilatant hardening can produce a slow slip response that also is associated with the absence of dynamic slip nucleation even if the applied shear stress is larger than the residual frictional strength of the fault (Ciardo & Lecampion, ; Zhang et al, ).…”

Section: Introductionmentioning

confidence: 99%

Changes of Slip Rate and Slip‐Plane Orientation by Fault Geometrical Complexities During Fluid Injection

Zhang

Jeffrey

et al. 2019

JGR Solid Earth

View full text Add to dashboard Cite

The injection‐induced slip of a fault containing along‐the‐fault geometrical complexities such as permeable cracks, dilational jogs and branches, was studied numerically using a plane‐strain hydraulic fracture model. The fault is modeled by placing complexities evenly spaced on either side of the inlet where fluid coming from a steady source is injected at a constant rate. The fault slip obeys the Coulomb friction law with slip weakening of the coefficient of friction. The applied shear stress is less than the residual fault strength, corresponding to a situation where a fault undergoes stable slip behind a slowly advancing rupture front. The numerical results show that the segments of complexity may not only delay slip zone extension and fluid flow, but temporarily increase slip rates. Short‐term faster slip rates occur after cracks and jogs are pressurized. The slip rate can reach values typical of microearthquake events, accompanied by rising and then dropping pressure and producing a stress release. Especially, the discontinuous slip sources are separated by the right‐angle jogs that do not slip. The slip on branches can be activated by fluid invasion and an associated normal effective stress reduction, and the slow slip sources eventually move from the fault to the branches. Even if a hydraulic fracturing treatment presents a low risk of generating dynamic slip, when fractures intersect faults containing geometrical complexities, fast slip events may be induced. The spatiotemporally varying slip rates and patterns presented provide an alternative interpretation for recorded seismic slip signals.

show abstract