Using the migration of the induced seismicity as a constraint for fractured Hot Dry Rock reservoir modelling

Bruel, Dominique

doi:10.1016/j.ijrmms.2007.07.001

Cited by 57 publications

(25 citation statements)

References 38 publications

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“…These changes facilitate shear slip in fractures that are favorably oriented in the anisotropic background stress field. This mechanism is known as effective stress reduction and has been identified as the major cause of induced seismicity in numerous modeling studies (Bruel, 2007;Kohl & Mégel, 2007;Rothert & Shapiro, 2003). The importance of stress redistribution following the shearing of rock for injection-induced seismicity has been emphasized (Catalli et al, 2016(Catalli et al, , 2013, and the stress alteration has been coupled with the fluid flow in several models (Baisch et al, 2010;McClure & Horne, 2011).…”

Section: Introductionmentioning

confidence: 99%

Postinjection Normal Closure of Fractures as a Mechanism for Induced Seismicity

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Berre

Keilegavlen

2017

Geophysical Research Letters

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Understanding the controlling mechanisms underlying injection‐induced seismicity is important for optimizing reservoir productivity and addressing seismicity‐related concerns related to hydraulic stimulation in Enhanced Geothermal Systems. Hydraulic stimulation enhances permeability through elevated pressures, which cause normal deformations and the shear slip of preexisting fractures. Previous experiments indicate that fracture deformation in the normal direction reverses as the pressure decreases, e.g., at the end of stimulation. We hypothesize that this normal closure of fractures enhances pressure propagation away from the injection region and significantly increases the potential for postinjection seismicity. To test this hypothesis, hydraulic stimulation is modeled by numerically coupling flow in the fractures and matrix, fracture deformation, and matrix deformation for a synthetic reservoir in which the flow and mechanics are strongly affected by a complex three‐dimensional fracture network. The role of the normal closure of fractures is verified by comparing simulations conducted with and without the normal closure effect.

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Section: Introductionmentioning

confidence: 99%

Postinjection Normal Closure of Fractures as a Mechanism for Induced Seismicity

Uçar

Berre

Keilegavlen

2017

Geophysical Research Letters

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“…(2) The statistical model should be capable of handling time-dependent stress changes and translate these into seismicity rate changes. The latter is needed as state-of-the-art geomechanical numerical reservoir models include a number of time-dependent processes such as pore pressure diffusion (linear and non-linear) coupled to the elastic response (Kohl and Mégel, 2007;McClure and Horne, 2011), the so-called pore pressure stress coupling process (Altmann et al, 2010;Ghassemi and Zhou, 2011;Hillis, 2000), thermal diffusion and combination of these processes on different time-scales for long-term production, stimulation and shut-in and re-injection of waste water (Baisch et al, 2010;Bruel, 2007;Rutqvist et al, 2007;Schoenball et al, 2010). Regardless of the complexity of the geomechanical-numerical reservoir model, the output is always at least a change of effective stress, both as a function of time and space.…”

Section: Introductionmentioning

confidence: 99%

“…Regardless of the complexity of the geomechanical-numerical reservoir model, the output is always at least a change of effective stress, both as a function of time and space. Deriving a synthetic catalogue of induced seismicity from these models is only possible by making further assumptions on the criticality of the reservoir, the failure criterion and the characteristics of the fracture network that determine the length of failure; i.e., the magnitude of the events (Bruel, 2007). In particular the a priori assumption on the distribution of the fracture network (length and density) and its initial stress field (e.g., criticality of the stress state) controls the frequency-magnitude -value and the seismicity rate.…”

Section: Introductionmentioning

confidence: 99%

Forward modelling of seismicity rate changes in georeservoirs with a hybrid geomechanical–statistical prototype model

et al. 2014

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. (2014): Forward modelling of seismicity rate changes in georeservoirs with a hybrid geomechanical-statistical prototype model. 52, A key challenge for the development of Enhanced Geothermal Systems (EGS) is to forecast the probability of occurrence of seismic events that have the potential to damage manmade structures. Induced seismicity results from man-made time-dependent stress changes, e.g., due to fluid injection, shut-in and fluid or steam production. To accomplish a classical Probabilistic Seismic Hazard Assessment (PSHA) a catalogue of induced seismicity is required. In addition, PSHA does not return any practical recommendation for how to treat the reservoir geomechanically in order to lower the probability of occurrence of induced seismicity. Thus, we propose to link the simulated stress changes from forward geomechanical numerical reservoir models with the statistical rate-and-state approach of Dieterich (1994). Using this link we translate the modelled time-dependent stress changes into time-dependent changes of seismicity rates. This approach is general and independent of the incorporated geomechanical numerical model used. We exemplify our hybrid model approach using a geomechanical model that describes the stimulation of the well GPK4 at the EGS site in Soultz-sous-Forêts (France) including the shut-in phase. By changing the injection rate in the geomechanical model we generate various synthetic injection scenarios. With these scenarios we can study the effect on the seismicity rate and provide a recommendation for which injection experiment results in the least increase of seismicity rate. The results indicate an explicit coupling between the time-depending stress changes and the induced seismicity rate for each scenario. Even though the hybrid model cannot be used in general to derive absolute values of the rate of induced seismicity a priori (this is only possible if the geomechanical model can be calibrated against observed induced events), it serves as a tool to test the effect of stress changes on the induced seismicity rate. The approach described here is a prototype model illustrating the general workflow. In particular the geomechanical model can be replaced by any other type of reservoir description.

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“…The corresponding geomechanical models contain different processes such as pore pressure diffusion (Kohl andMégel 2007, McClure andHorne 2011), the pore pressure stress coupling process (Altmann et al 2010, Hillis 2000), thermal diffusion and combination of these processes (Baisch et al 2010, Bruel 2007, Rutqvist et al 2007, Schoenball et al 2010). The outputs of these models are in form of spatio-temporal stress changes in the reservoir.…”

Section: Introductionmentioning

confidence: 99%

“…Induced seismicity can be simulated from the stress changes (obtained from geomechanical model) only by considering additional processes and assumptions on the parameters corresponding to the failure processes (Bruel 2007). The actual rupture process has already been simulated for 2D reservoir models .…”

Section: Introductionmentioning

confidence: 99%

Particle Based Discrete Element Modeling of Hydraulic Stimulation of Geothermal Reservoirs, Induced Seismicity and Fault Zone Deformation

Yoon

Hakimhashemi²,

Zang³

et al. 2013

Journal of Korean Society For Rock Mechanics

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This numerical study investigates seismicity and fault slip induced by fluid injection in deep geothermal reservoir with pre-existing fractures and fault. Particle Flow Code 2D is used with additionally implemented hydro-mechanical coupled fluid flow algorithm and acoustic emission moment tensor inversion algorithm. The output of the model includes spatio-temporal evolution of induced seismicity (hypocenter locations and magnitudes) and fault deformation (failure and slip) in relation to fluid pressure distribution. The model is applied to a case of fluid injection with constant rates changing in three steps using different fluid characters, i.e. the viscosity, and different injection locations. In fractured reservoir, spatio-temporal distribution of the induced seismicity differs significantly depending on the viscosity of the fracturing fluid. In a fractured reservoir, injection of low viscosity fluid results in larger volume of induced seismicity cloud as the fluid can migrate easily to the reservoir and cause large number and magnitude of induced seismicity in the post-shut-in period. In a faulted reservoir, fault deformation (co-seismic failure and aseismic slip) can occur by a small perturbation of fracturing fluid (<0.1 MPa) can be induced when the injection location is set close to the fault. The presented numerical model technique can practically be used in geothermal industry to predict the induced seismicity pattern and magnitude distribution resulting from hydraulic stimulation of geothermal reservoirs prior to actual injection operation.

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Using the migration of the induced seismicity as a constraint for fractured Hot Dry Rock reservoir modelling

Cited by 57 publications

References 38 publications

Postinjection Normal Closure of Fractures as a Mechanism for Induced Seismicity

Postinjection Normal Closure of Fractures as a Mechanism for Induced Seismicity

Forward modelling of seismicity rate changes in georeservoirs with a hybrid geomechanical–statistical prototype model

Particle Based Discrete Element Modeling of Hydraulic Stimulation of Geothermal Reservoirs, Induced Seismicity and Fault Zone Deformation

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