Large-Scale Explosion and Induced Seismicity: Geological, Structural, and Hydrogeological Impacts

2021 ◽  
Author(s):  
Ella Gorbunova
Keyword(s):  
Induced Seismicity ◽  
Large Scale

scholarly journals Full-waveform-based characterization of acoustic emission activity in a mine-scale experiment: a comparison of conventional and advanced hydraulic fracturing schemes

2020 ◽  
Vol 222 (1) ◽  
pp. 189-206 ◽  
Author(s):  
Peter Niemz ◽  
Simone Cesca ◽  
Sebastian Heimann ◽  
Francesco Grigoli ◽  
Sebastian von Specht ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Hydraulic Fracturing ◽  
Induced Seismicity ◽  
Large Scale ◽  
Sampling Rate ◽  
Fracture Plane ◽  
B Values ◽  
Full Waveform ◽  
Scale Experiment ◽  
Fracturing Experiments

SUMMARY Understanding fracturing processes and the hydromechanical relation to induced seismicity is a key question for enhanced geothermal systems (EGS). Commonly massive fluid injection, predominately causing hydroshearing, are used in large-scale EGS but also hydraulic fracturing approaches were discussed. To evaluate the applicability of hydraulic fracturing techniques in EGS, six in situ, multistage hydraulic fracturing experiments with three different injection schemes were performed under controlled conditions in crystalline rock at the Äspö Hard Rock Laboratory (Sweden). During the experiments the near-field ground motion was continuously recorded by 11 piezoelectric borehole sensors with a sampling rate of 1 MHz. The sensor network covered a volume of 30×30×30 m around a horizontal, 28-m-long injection borehole at a depth of 410 m. To extract and characterize massive, induced, high-frequency acoustic emission (AE) activity from continuous recordings, a semi-automated workflow was developed relying on full waveform based detection, classification and location procedures. The approach extended the AE catalogue from 196 triggered events in previous studies to more than 19 600 located AEs. The enhanced catalogue, for the first time, allows a detailed analysis of induced seismicity during single hydraulic fracturing experiments, including the individual fracturing stages and the comparison between injection schemes. Beside the detailed study of the spatio-temporal patterns, event clusters and the growth of seismic clouds, we estimate relative magnitudes and b-values of AEs for conventional, cyclic progressive and dynamic pulse injection schemes, the latter two being fatigue hydraulic fracturing techniques. While the conventional fracturing leads to AE patterns clustered in planar regions, indicating the generation of a single main fracture plane, the cyclic progressive injection scheme results in a more diffuse, cloud-like AE distribution, indicating the activation of a more complex fracture network. For a given amount of hydraulic energy (pressure multiplied by injected volume) pumped into the system, the cyclic progressive scheme is characterized by a lower rate of seismicity, lower maximum magnitudes and significantly larger b-values, implying an increased number of small events relative to the large ones. To our knowledge, this is the first direct comparison of high resolution seismicity in a mine-scale experiment induced by different hydraulic fracturing schemes.

Towards coupling fluid flow and rate-and-state friction in compacting visco-poro-elasto-plastic reservoirs

2020 ◽  
Author(s):  
Mohsen Goudarzi ◽  
Ylona van Dinther ◽  
Meng Li ◽  
René de Borst ◽  
Casper Pranger ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Induced Seismicity ◽  
Large Scale ◽  
Bulk Material ◽  
Frictional Heating ◽  
Fluid Pressure ◽  
Gas Production ◽  
Modeling Framework ◽  
Fully Coupled

<p>Induced seismicity as a result of natural gas production is a major challenge from both an industrial and a societal perspective. The compaction caused by gas production leads to changes of the effective pressure fields in the reservoir and stress redistributions occur particularly in the surrounding faults. In addition, the strong coupling between fluid flow and solid rock deformations and the role of fluid flow regarding the frictional properties of the faults necessitate a coupled and comprehensive modeling framework. A general and fully coupled thermo-hydro-mechanical finite difference formulation is developed herein and the results are verified against numerical benchmarks. A visco-elasto-plastic rheological behavior is assumed for the bulk material and a return-mapping algorithm is implemented for accurate simulation of the stress evolution. The geometrical features of the faults are incorporated into a regularized continuum framework, while the response of the fault zone is governed by a rate-and-state-dependent friction model. Numerical simulations are provided for large-scale problems and their efficiency is assured through the evaluation of the consistently linearized systems of equations along with the use of advanced numerical solvers and parallel computing. Although the proposed framework is a step towards the modeling of earthquake sequences for induced seismicity applications, the features of the numerical model are highlighted for other applications, including seismic events in subduction settings where the role of fluid flow inside the faults is considerable. Another application of the present, fully coupled hydro-thermo-mechanical formulation is the prediction of the fluid pressurization phenomena, where the frictional heating increases the magnitude of the pore fluid pressure inside the faults, and the resultant degradation of dynamic frictional strength is naturally captured. </p>

Investigation of injection-induced seismicity using a coupled fluid flow and rate/state friction model

Geophysics ◽  
2011 ◽  
Vol 76 (6) ◽  
pp. WC181-WC198 ◽  
Author(s):  
Mark W. McClure ◽  
Roland N. Horne
Keyword(s):  
Fluid Flow ◽  
Induced Seismicity ◽  
Large Scale ◽  
Injection Pressure ◽  
Friction Model ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Isolated Fracture ◽  
Lower Magnitude ◽  
Event Magnitude

We describe a numerical investigation of seismicity induced by injection into a single isolated fracture. Injection into a single isolated fracture is a simple analog for shear stimulation in enhanced geothermal systems (EGS) during which water is injected into fractured, low permeability rock, triggering slip on preexisting large scale fracture zones. A model was developed and used that couples (1) fluid flow, (2) rate and state friction, and (3) mechanical stress interaction between fracture elements. Based on the results of this model, we propose a mechanism to describe the process by which the stimulated region grows during shear stimulation, which we refer to as the sequential stimulation (SS) mechanism. If the SS mechanism is realistic, it would undermine assumptions that are made for the estimation of the minimum principal stress and unstimulated hydraulic diffusivity. We investigated the effect of injection pressure on induced seismicity. For injection at constant pressure, there was not a significant dependence of maximum event magnitude on injection pressure, but there were more relatively large events for higher injection pressure. Decreasing injection pressure over time significantly reduced the maximum event magnitude. Significant seismicity occurred after shut-in, which was consistent with observations from EGS stimulations. Production of fluid from the well immediately after injection inhibited shut-in seismic events. The results of the model in this study were found to be broadly consistent with results from prior work using a simpler treatment of friction that we refer to as static/dynamic. We investigated the effect of shear-induced pore volume dilation and the rate and state characteristic length scale, [Formula: see text]. Shear-induced pore dilation resulted in a larger number of lower magnitude events. A larger value of [Formula: see text] caused slip to occur aseismically.

scholarly journals ETAS Space time modelling of Chile induced seismicity using covariates.

2021 ◽  
Author(s):  
Marcello Chiodi ◽  
Orietta Nicolis ◽  
Giada Adelfio ◽  
Nicoletta D'angelo ◽  
Alex Gonzàlez
Keyword(s):  
Time Scale ◽  
Seismic Activity ◽  
Induced Seismicity ◽  
Large Scale ◽  
Space Time ◽  
Expected Number ◽  
Statistical Point ◽  
Linear Predictor ◽  
Etas Model ◽  
Aftershock Sequences

<p>Chilean seismic activity is among the strongest ones in the world. As already shown in previous papers, seismic activity can be usefully described by a space-time branching process, like the ETAS (Epidemic Type Aftershock Sequences) model, which is a semiparametric model with a large time scale component for the background seismicity and a small time scale component for the induced seismicity. The large-scale component intensity function  is usually estimated by  nonparametric techniques, specifically in our paper we used the Forward Likelihood Predictive approach (FLP); the induced seismicity is modelled with a parametric space-time function. In classical ETAS models the expected number of induced events depends only on the magnitude of the main event. From a statistical point of view, forecast of induced seismicity can be performed in the days following a big event; of course the estimation of this component is very important to forecast the evolution, in space and time domain, of a seismic sequence. Together with magnitude, to explain the expected number of induced events we also used other covariates. According to this formulation, the expected number of events induced by event E<sub>i </sub>is a function of a linear predictor η<sub>i</sub>=<strong>x<sub>i</sub></strong><strong>β, </strong>where <strong>x<sub>i </sub></strong>is the vector of covariates observed for the i-th event (the first is usually the magnitude m<sub>i</sub>), and <strong>β</strong> is a vector of parameters to be estimated together with the other parametric and nonparametric components of the ETAS model. We obtained some interesting result using some covariates related to the depth of events and to some GPS measurement, corresponding to earth movement observed before main events. We find that some of these models can improve the description and the forecasting of the induced seismicity in Chile, after a subdivision of the country in different spatial regions. We used open-source software (R package etasFLP) to perform the semiparametric estimation of the ETAS model with covariates.</p>

Earthquake-earthquake triggering in natural swarms and fluid-induced seismicity

2020 ◽  
Author(s):  
Kamran Karimi ◽  
Joern Davidsen
Keyword(s):  
Long Range ◽  
Seismic Activity ◽  
Induced Seismicity ◽  
Large Scale ◽  
Underlying Structure ◽  
Driving Mechanism ◽  
Earthquake Triggering ◽  
Long Valley Caldera ◽  
Event Triggering ◽  
Tectonic Settings

<p>Aftershock cascades and aftershock zones play an important role in forecasting seismic activity in both natural and human-made situations. While their behavior including the spatial aftershock zone scaling has been the focus of many studies in tectonic settings finding, for example, long-range earthquake-earthquake triggering in the near-field, this is not the case in situations where the seismic activity is primarily driven by fluids and the diffusion of excessive pore pressure. Here, we probe three different seismic settings that are believed to be influenced by fluid diffusion. The natural swarm in i) the Long Valley Caldera and the suspected swarms in ii) the Yuha Desert, both located in California, and associated earthquake-earthquake triggering behavior are compared against induced seismicity related to large scale wastewater disposal in iii) Oklahoma and southern Kansas. All settings exhibit a significant amount of event-event triggering highlighting the importance of secondary processes for the overall seismicity. We find an almost identical temporal event-event triggering behavior including the Omori-Utsu relation and the associated productivity relation. In terms of the spatial triggering density, both cases i) and iii) show a rapid decay beyond their rupture length. This proves that narrow spatial “aftershock” zones are not specific to induced seismicity but also occur in natural settings. Typical of most tectonic settings, a relatively long-range behavior is observed in case ii) suggesting that fluid migration might not be the dominant driving mechanism of the seismic activity and/or that the underlying structure of the fault network may control the secondary earthquake-earthquake triggering and its spatial evolution.</p>

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