scholarly journals Hydro-mechanical modeling of seismogenic asperity loaded by aseismic slip through TOUGH-BIEM simulation

2020 ◽  
Author(s):  
Hideo Aochi ◽  
Jonny Rutqvist
Keyword(s):  
Pore Pressure ◽  
Injection Rate ◽  
Friction Model ◽  
Fault Slip ◽  
Boundary Integral ◽  
Fluid Volume ◽  
Fault Reactivation ◽  
Pressure Increase ◽  
Aseismic Slip ◽  
Stress Dependent

<p>We consider seismogenic asperities loaded by aseismic slip on a fault, which is induced by fluid circulation, as a simple example of fault reactivation. For this purpose, we combine two methods. The TOUGH2 (Transport Of Unsaturated Ground water and Heat) code is used for modeling the pore pressure evolution within a fault and then a Boundary Integral Equation Method (BIEM) is applied for simulating fault slip, including aseismic slip on the entire fault plane and fast slip on seismogenic asperities. The fault permeability is assumed stress-dependent and therefore is not constant but varies during a simulation. We adopt the Coulomb friction and a cyclic slip-strengthening-then-weakening friction model governing the fault slip, which allows for repeated asperity slip. We were able to demonstrate the entire process from the fluid injection, pore pressure increase, aseismic slip to seismogenic asperity slip. We tested a step-like increase of injection rate with time, which is common for hydraulic fracturing and reservoir stimulation at deep geothermal sites. Under this configuration, the pore pressure increase is not proportional to the injection rate, as the permeability depends on the stress.  Fault slip on seismogenic asperities is triggered repeatedly by surrounding aseismic slip. We find, in a given example, that the reccurence of the fast slip on asperity is approximatively proportional to the injected fluid volume, inferring that the aseismic slip amount increases proporitionally to the fluid volume as well.</p>

Integrated Reservoir Geomechanics Approach for Reservoir Management

2021 ◽  
Author(s):  
Vai Yee Hon ◽  
M Faizzudin Mat Piah ◽  
Noor 'Aliaa M Fauzi ◽  
Peter Schutjens ◽  
Binayak Agarwal ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Water Injection ◽  
Fluid Pressure ◽  
Integrated Approach ◽  
Fault Slip ◽  
Fault Reactivation ◽  
Analytical Models ◽  
Reservoir Compaction ◽  
Stress Changes ◽  
Reservoir Geomechanics

Abstract An integrated 3D dynamic reservoir geomechanics model can provide a diverse 3D view of depletion-injection-induced field stress changes and the resulting deformation of both reservoir and overburden formations at various field locations. It enables the assessment of reservoir compaction, platform site subsidence, fault reactivation and caprock integrity associated with multiple production and injection reservoirs of the field. We demonstrated this integrated approach for a study field located in the South China Sea, Malaysia, which is planned for water injection for pressure support and EOR scheme thereafter. Reservoir fluid containment during water injection is an important concern because of the intensive geologic faulting and fracturing in the collapsed anticlinal structure, with some faults extending from the reservoirs to shallow depths at or close to the seafloor. Over 30 simulations were done, and most input parameters were systematically varied to gain insight in their effect on result that was of most interest to us: The tendency of fault slip as a function of our operation-induced variations in pore pressure in the reservoir rocks bounding the fault, both during depletion and injection. The results showed that depletion actually reduces the risk of fault slip and of the overburden, while injection-induced increase in pore fluid pressure will lead to a significant increase in the risk of fault slip. Overall, while depletion appears to stabilize the fault and injection appears to destabilize the fault, no fault slip is predicted to occur, not even after a 900psi increase in pore pressure above the pore pressure levels at maximum depletion. We present the model results to demonstrate why depletion and injection have such different effects on fault slip tendency. The interpretation of these geomechanical model results have potential applications beyond the study field, especially for fields with a similar geology and development plan. This is a novel application of 3D dynamic reservoir geomechanics model that cannot be obtained from 1D analytical models alone.

scholarly journals Non-linear effects of pore pressure increase on seismic event generation in a multi-degree-of-freedom rate-and-state model of tectonic fault sliding

2017 ◽  
Vol 24 (2) ◽  
pp. 215-225 ◽  
Author(s):  
Sergey B. Turuntaev ◽  
Vasily Y. Riga
Keyword(s):  
Pore Pressure ◽  
Seismic Event ◽  
Friction Model ◽  
Degree Of Freedom ◽  
Pressure Increase ◽  
Fluid Injection ◽  
Model Parameters ◽  
Tectonic Fault ◽  
Rate And State Friction ◽  
Linear Effects

Abstract. The influence of fluid injection on tectonic fault sliding and seismic event generations was studied by a multi-degree-of-freedom rate-and-state friction model with a two-parametric friction law. A system of blocks (up to 25 blocks) elastically connected to each other and connected by elastic springs to a constant-velocity moving driver was considered. Variation of the pore pressure due to fluid injection led to variation of effective stress between the first block and the substrate. Initially the block system was in a steady-sliding state; then, its state was changed by the pore pressure increase. The influence of the model parameters (number of blocks, spring stiffness, velocity weakening parameter) on the seismicity variations was considered. Various slip patterns were obtained and analysed.

scholarly journals Non-linear effects of pore pressure increase on seismic event generation in multi-degree-of-freedom rate-and-state model of tectonic fault sliding

2016 ◽  
Author(s):  
Sergey B. Turuntaev ◽  
Vasily Y. Riga
Keyword(s):  
Pore Pressure ◽  
Friction Model ◽  
Degree Of Freedom ◽  
Pressure Increase ◽  
Fluid Injection ◽  
Model Parameters ◽  
Tectonic Fault ◽  
Rate And State Friction ◽  
Linear Effects ◽  
Event Generation

Abstract. The influence of fluid injection on tectonic fault sliding and generation of seismic events was studied by multi-degree-of-freedom rate-and-state friction model with two-parametric friction law. A system of blocks (up to 25 blocks) elastically connected with each other and connected by elastic springs to a constant-velocity moving driver was considered. Variation of the pore pressure due to fluid injection led to variation of effective stress between the first block and the substrate. Initially the block system was in steady-sliding state, then its state was changed by the pore pressure increase. The influence of the model parameters (number of the blocks, the spring stiffness, velocity weakening parameter) on the seismicity variations were considered. Various slip patterns were obtained and analysed.

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 Fault reactivation and strain partitioning across the brittle-ductile transition

Geology ◽  
2019 ◽  
Vol 47 (12) ◽  
pp. 1127-1130 ◽  
Author(s):  
Gabriel G. Meyer ◽  
Nicolas Brantut ◽  
Thomas M. Mitchell ◽  
Philip G. Meredith
Keyword(s):  
Fault Slip ◽  
Fault Reactivation ◽  
Ductile Deformation ◽  
Tectonic Deformation ◽  
Gradual Change ◽  
Bulk Rock ◽  
Total Deformation ◽  
Bulk Strain ◽  
Brittle Ductile Transition ◽  
Ductile Flow

Abstract The so-called “brittle-ductile transition” is thought to be the strongest part of the lithosphere, and defines the lower limit of the seismogenic zone. It is characterized not only by a transition from localized to distributed (ductile) deformation, but also by a gradual change in microscale deformation mechanism, from microcracking to crystal plasticity. These two transitions can occur separately under different conditions. The threshold conditions bounding the transitions are expected to control how deformation is partitioned between localized fault slip and bulk ductile deformation. Here, we report results from triaxial deformation experiments on pre-faulted cores of Carrara marble over a range of confining pressures, and determine the relative partitioning of the total deformation between bulk strain and on-fault slip. We find that the transition initiates when fault strength (σf) exceeds the yield stress (σy) of the bulk rock, and terminates when it exceeds its ductile flow stress (σflow). In this domain, yield in the bulk rock occurs first, and fault slip is reactivated as a result of bulk strain hardening. The contribution of fault slip to the total deformation is proportional to the ratio (σf − σy)/(σflow − σy). We propose an updated crustal strength profile extending the localized-ductile transition toward shallower regions where the strength of the crust would be limited by fault friction, but significant proportions of tectonic deformation could be accommodated simultaneously by distributed ductile flow.

Adhesive and normal stress-dependent dynamic friction of a gelatin hydrogel

2021 ◽  
pp. 135065012110446
Author(s):  
Nitish Sinha ◽  
Arun Kumar Singh ◽  
Vinit Gupta ◽  
Jitendra Kumar Katiyar
Keyword(s):  
Experimental Data ◽  
Normal Stress ◽  
Scaling Law ◽  
Shear Velocity ◽  
Friction Model ◽  
Dynamic Friction ◽  
Practical Applications ◽  
Soft Solids ◽  
Gelatin Hydrogel ◽  
Stress Dependent

Adhesion and friction of soft solids on hard surfaces are the important properties for a variety of practical applications. In the present study, Coulomb's law of friction is used for characterizing adhesive friction as well as normal stress-dependent dynamic friction of a gelatin hydrogel on a fixed glass surface. The experimental data, concerning normal stress-dependent dynamic friction of different shear velocity, are obtained from literature. It is observed that both components of friction increase with shear velocity. More importantly, the scaling law shows that adhesive stress varies almost linearly with corresponding coefficient of friction of the hydrogel. A dynamic friction model is also used to analyze the same experimental data to predict a negative normal stress at which dynamic friction reduces to zero, and this result matches closely with the experimental value.

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