A Novel Coupled Approach to Investigate the Spatiotemporal Evolution of Fracturing-Induced Seismicity: Case Study

2021 ◽  
Author(s):  
Gang Hui ◽  
Shengnan Chen ◽  
Fei Gu
Keyword(s):  
Hydraulic Fracturing ◽  
Induced Seismicity ◽  
Spatiotemporal Pattern ◽  
Hydraulic Fractures ◽  
Spatiotemporal Evolution ◽  
Coupled Flow ◽  
Seismicity Rate ◽  
Failure State ◽  
Pkn Model

Abstract The recent seismicity rate increase in Fox Creek is believed to be linked to the hydraulic fracturing operations near the region. However, the spatiotemporal evolution of hydraulic fracturing-induced seismicity is not well understood. Here, a coupled approach of geology, geomechanics, and hydrology is proposed to characterize the spatiotemporal evolution of hydraulic fracturing-induced seismicity. The seismogenic faults in the vicinity of stimulated wells are derived from the focal mechanisms of mainshock event and lineament features of induced events. In addition, the propagation of hydraulic fractures is simulated by using the PKN model, in combination with inferred fault, to characterize the possible well-fault hydrological communication. The original stress state of inferred fault is determined based on the geomechanics analysis. Based on the poroelasticity theory, the coupled flow-geomechanics simulation is finally conducted to quantitatively understand the fluid diffusion and poroelastic stress perturbation in response to hydraulic fracturing. A case study of a moment-magnitude-3.4 earthquake near Fox Creek is utilized to demonstrate the applicability of the coupled approach. It is shown that hydraulic fractures propagated along NE45° and connected with one North-south trending fault, causing the activation of fault and triggered the large magnitude event during fracturing operations. The barrier property of inferred fault under the strike-slip faulting regime constrains the nucleation position of induced seismicity within the injection layer. The combined changes of pore pressure and poroelastic stress caused the inferred fault to move towards the failure state and triggered the earthquake swarms. The associated spatiotemporal changes of Coulomb Failure Stress along the fault plane is well in line with the spatiotemporal pattern of induced seismicity in the studied case. Risks of seismic hazards could be reduced by decreasing fracturing job size during fracturing stimulations.

Normal faulting activated by hydraulic fracturing: A case study from the Barnett Shale, Fort Worth Basin

2020 ◽  
Vol 39 (3) ◽  
pp. 204-211
Author(s):  
Dmitry Alexandrov ◽  
Leo Eisner ◽  
Umair bin Waheed ◽  
SanLinn Isma'il Ebrahim Kaka ◽  
Stewart Alan Greenhalgh
Keyword(s):  
Hydraulic Fracturing ◽  
Horizontal Resolution ◽  
Source Mechanism ◽  
Barnett Shale ◽  
Hydraulic Fractures ◽  
Normal Faulting ◽  
Fort Worth Basin ◽  
Economic Methods ◽  
Source Mechanisms

Surface microseismic arrays enable long-term field-scale monitoring over multiple stimulations during the life of an unconventional field. In this study, we show highly economic methods of monitoring with sparse surface arrays in the Barnett Shale and develop an alternatative method of processing to enable good vertical and horizontal resolution of located events. We show that sparse surface monitoring arrays enable not only the detection and location of high numbers of microseismic events but also source mechanism characterization. This case study illustrates how hydraulic fracturing activated normal faulting at a distance of approximately 1 mile from stimulated wells. We show that the source mechanism enables us to resolve between newly created hydraulic fractures and activated faults. The differences in source mechanisms and b-values of newly created fractures and activated faults are consistent with independently processed temporary star-like arrays, which are also deployed over the same stimulation.

Seismic b-value within the Montney Play of Northeast British Columbia, Canada

2021 ◽  
Author(s):  
Alireza Babaie Mahani
Keyword(s):  
British Columbia ◽  
Hydraulic Fracturing ◽  
Induced Seismicity ◽  
B Value ◽  
Systematic Difference ◽  
Magnitude Distribution ◽  
Seismicity Rate ◽  
Northern Area ◽  
Seismicity Rates ◽  
Frequency Magnitude Distribution

Critical analysis of induced earthquake occurrences requires comprehensive datasets obtained by dense seismographic networks. In this study, using such datasets, I take a detailed investigation into induced seismicity that occurred in the Montney play of northeast British Columbia, mostly caused by hydraulic fracturing. The frequency-magnitude distribution (FMD) of earthquakes in several temporal and spatial clusters, show fundamental discrepancies between seismicity in the southern Montney play (2014-2018) and the northern area (2014-2016). In both regions, FMDs follow the linear Gutenberg-Richter (G-R) relationship for magnitudes up to 2-3. While in the southern Montney, within the Fort St. John graben complex, the number of earthquakes at larger magnitudes falls off rapidly below the G-R line, within the northern area with a dominant compressional regime, the number of events increases above the G-R line. This systematic difference may have important implications with regard to seismic hazard assessments from induced seismicity in the two regions, although caution in the interpretation is warranted due to local variabilities. While for most clusters within the southern Montney area, the linear or truncated G-R relationship provide reliable seismicity rates for events below magnitude 4, the G-R relationship underestimates the seismicity rate for magnitudes above 3 in northern Montney. Using a well-located dataset of earthquakes in southern Montney, one can observe generally that 1) seismic productivity correlates well with the injected volume during hydraulic fracturing and 2) there is a clear depth dependence for the G-R b-value; clusters with deeper median depths show lower b-values than those with shallower depths.

Spatiotemporal modelling of induced seismicity with a stress-based statistical approach applied to different production sites

2020 ◽  
Author(s):  
Gudrun Richter ◽  
Sebastian Hainzl ◽  
Peter Niemz ◽  
Francesca Silverii ◽  
Torsten Dahm ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Induced Seismicity ◽  
Gas Storage ◽  
Spatiotemporal Pattern ◽  
Model Parameters ◽  
Storage Site ◽  
Data Set ◽  
Wide Range ◽  
Stress Changes ◽  
Gas Fields

<p>In the framework of the Geo:N project SECURE (Sustainable dEployment and Conservation of Underground Reservoirs and Environment) we developed a Python software toolbox to model the rate and distribution of seismicity induced by anthropogenic stress changes at various production sites (gas production, hydrofracturing, gas storage). This toolbox tests different frictional behavior of the underground (linear or rate-and-state stressing rate dependent, critically or subcritically prestressed faults) and takes into account the uncertainties of the production site parameters. The knowledge on the location and orientation of pre-existing faults can be considered as well. Model parameters are estimated by fitting the model to recorded historical seismicity using a maximum likelihood approach. We discuss applications at conventional gas fields, hydraulic fracturing experiments and an aquifer gas storage site, covering a wide range of spatial and temporal scales of induced seismicity in different settings and for different production schemes. This enables to investigate the underlying physical processes by the comparison of the different models. Additionally, the model parameters are linked to frictional material properties and the best performing model can be used to forecast the seismicity rates in space and time with their uncertainties according to the production plans.</p><p>Induced seismicity at gas fields in the Northern Netherlands and in Germany have similar tectonic settings but very different extents, depths and production histories. The data set of two sites are compared which both show a large delay of the first recorded seismicity after the start of production. Using our model we can reproduce the long delay for both sites. Thanks to the long and detailed data set we successfully reproduce the spatiotemporal pattern of the seismicity of one site, whereas the limited number of seismic events result in large uncertainties for the other site. In the comparative testing of the models the critically prestressed rate-and-state model performs best. This means that the complete stressing history influences the resulting seismicity. We also applied the model to a hydraulic fracturing experiment in granite comparing data sets for different fracturing methods and different phases of a stimulation experiment. Hundreds of microearthquakes are localized in a volume of roughly 15x15m with increasing number of events for later refraction stages indicating the growth of rock fracturing. A third application is run for a gas storage in an aquifer layer, which is loaded by injection and production operations. Here the proportion of the tectonic versus the anthropogenic induced seismicity is investigated analyzing the varying number of small local earthquakes in the region.</p>

scholarly journals Fault Triggering Mechanisms for Hydraulic Fracturing-Induced Seismicity From the Preston New Road, UK Case Study

2021 ◽  
Vol 9 ◽  
Author(s):  
Tom Kettlety ◽  
James P. Verdon
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Induced Seismicity ◽  
Elastic Stress ◽  
Fluid Pressure ◽  
Stress Transfer ◽  
Fault Reactivation ◽  
Hydraulic Fractures ◽  
Fracture Opening ◽  
Triggering Mechanisms

We investigate the physical mechanisms governing the activation of faults during hydraulic fracturing. Recent studies have debated the varying importance of different fault reactivation mechanisms in different settings. Pore pressure increase caused by injection is generally considered to be the primary driver of induced seismicity. However, in very tight reservoir rocks, unless a fracture network exists to act as a hydraulic conduit, the rate of diffusion may be too low to explain the spatio-temporal evolution of some microseismic sequences. Thus, elastic and poroelastic stress transfer and aseismic slip have been invoked to explain observations of events occurring beyond the expected distance of a reasonable diffusive front. In this study we use the high quality microseismic data acquired during hydraulic fracturing at the Preston New Road (PNR) wells, Lancashire, UK, to examine fault triggering mechanisms. Injection through both wells generated felt induced seismicity—an ML 1.6 during PNR-1z injection in 2018 and an ML 2.9 during PNR-2 in 2019—and the microseismic observations show that each operation activated different faults with different orientations. Previous studies have already shown that PNR-1z seismicity was triggered by a combination of both direct hydraulic effects and elastic stress transfer generated by hydraulic fracture opening. Here we perform a similar analysis of the PNR-2 seismicity, finding that the PNR-2 fault triggering was mostly likely dominated by the diffusion of increased fluid pressure through a secondary zone of hydraulic fractures. However, elastic stress transfer caused by hydraulic fracture opening would have also acted to promote slip. It is significant that no microseismicity was observed on the previously activated fault during PNR-2 operations. This dataset therefore provides a unique opportunity to estimate the minimum perturbation required to activate the fault. As it appears that there was no hydraulic connection between them during each stimulation, any perturbation caused to the PNR-1z fault by PNR-2 stimulation must be through elastic or poroelastic stress transfer. As such, by computing the stress transfer created by PNR-2 stimulation onto the PNR-1z fault, we are able to approximate the minimum bound for the required stress perturbation: in excess of 0.1 MPa, orders of magnitude larger than stated estimates of a generalized triggering threshold.

A Long-Lived Swarm of Hydraulic Fracturing-Induced Seismicity Provides Evidence for Aseismic Slip

2020 ◽  
Vol 110 (5) ◽  
pp. 2205-2215 ◽  
Author(s):  
Thomas S. Eyre ◽  
Megan Zecevic ◽  
Rebecca O. Salvage ◽  
David W. Eaton
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Induced Seismicity ◽  
Aftershock Sequence ◽  
Fluid Migration ◽  
Aseismic Slip ◽  
Seismicity Rate ◽  
Slow Earthquakes ◽  
Seismic Swarms ◽  
Event Distribution

ABSTRACT Seismic swarms are defined as an increase in seismicity that does not show a clear mainshock–aftershock sequence. Typically, swarms are primarily associated with either fluid migration or slow earthquakes (aseismic slip). In this study, we analyze a swarm induced by hydraulic fracturing (HF) that persisted for an unusually long duration of more than 10 months. Swarms ascribed to fluid injection are usually characterized by an expanding seismicity front; in this case, however, characteristics such as a relatively steady seismicity rate over time and lack of hypocenter migration cannot be readily explained by a fluid-diffusion model. Here, we show that a different model for HF-induced seismicity, wherein an unstable region of a fault is loaded by proximal, pore-pressure-driven aseismic slip, better explains our observations. According to this model, the steady seismicity rate can be explained by a steady slip velocity, while the spatial stationarity of the event distribution is due to lateral confinement of the creeping region of the fault with increased pore pressure. Our results may have important implications for other induced or natural seismic swarms, which could be similarly explained by aseismic loading of asperities driven by fluid overpressure rather than the often-attributed fluid-migration model.

Numerical Analysis of the Induced Seismicity Triggered by Hydraulic Fracturing in the Duvernay Formation in Alberta, CA

2021 ◽  
Author(s):  
Dima Yassine ◽  
Alissar Yehya ◽  
Elsa Maalouf
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Observational Data ◽  
Induced Seismicity ◽  
Oil And Gas ◽  
The United States ◽  
Gas Production ◽  
Hydraulic Fractures ◽  
Seismic Events ◽  
Induced Earthquakes

<p>In the past decades, induced seismicity has become a major concern due to its correlation with oil and gas production and wastewater disposal. Unlike the induced seismicity observed in the United States that is associated with massive saltwater disposal, the induced seismicity observed in the Duvernay formation, a shale target in Alberta, Western Canada, is associated with hydraulic fracturing operations. In this work, we explore the possible mechanisms and the hydro-geological factors responsible for the seismic events that occurred between 2014 and 2015 in the Duvernay formation. By a two-dimensional finite element poroelastic model, using COMSOL Multiphysics, we couple fluid flow and solid deformation to estimate the change in the Coulomb Failure Stress (CFS) along two critically stressed faults existing near the hydraulic fracturing operations. One fault (Fault 1) is 1.01 km away from the location of hydraulic fractures while the second fault (Fault 2) is 0.425 km below the location of hydraulic fractures. The variations of the CFS along the two pre-existing faults are analyzed and compared to the seismic events obtained from the observational data in the Duvernay formation from December 2014 to March 2015 (Bao & Eaton, 2016). Our results show that most of the seismic events correlate spatially and temporally with positive CFS values that imply a risk of failure. During the early stages of hydraulic fracturing, the triggering failure mechanism of “Fault 1” is the increase in the shear stress on portions of the fault that are under extension and that of “Fault 2” is the pore pressure diffusion. Moreover, the distance between the centers of the two faults must range between 1.5 km and 2 km for the CFS results to agree with the observed seismic events. Under this condition, the shallower sections of “Fault 1” are under compression and show a stabilizing behavior (i.e., negative CFS) that is confirmed by the lack of seismic events from observational data, and the deeper sections of “Fault 1” are under extension and show a destabilizing behavior (i.e., positive CFS), which correlates with the measured seismic events. If the distance between “Fault 1” and “Fault 2” is less than 1.5 km, the shallower section of “Fault 1” would be destabilized by the effect of pore pressure, which does not agree with the observed seismic data. Moreover, if the distance between “Fault 1” and “Fault 2” is greater than 2 km, “Fault 1” would be entirely stabilized. Hence, the position of the faults with respect to the location of the hydraulic fracturing operations played an important role in the induced earthquakes triggering mechanisms and in the spatiotemporal distribution of the seismic events.</p>

Varied Responses to Human-Induced Seismicity in the City of Azle, Texas

2019 ◽  
Vol 3 (1) ◽  
pp. 1-8
Author(s):  
Sarmistha R. Majumdar
Keyword(s):  
State Government ◽  
Induced Seismicity ◽  
Oil And Gas ◽  
The United States ◽  
The State ◽  
Prior History ◽  
Small Community ◽  
Regulatory Policies ◽  
The Status

Fracking has helped to usher in an era of energy abundance in the United States. This advanced drilling procedure has helped the nation to attain the status of the largest producer of crude oil and natural gas in the world, but some of its negative externalities, such as human-induced seismicity, can no longer be ignored. The occurrence of earthquakes in communities located at proximity to disposal wells with no prior history of seismicity has shocked residents and have caused damages to properties. It has evoked individuals’ resentment against the practice of injection of fracking’s wastewater under pressure into underground disposal wells. Though the oil and gas companies have denied the existence of a link between such a practice and earthquakes and the local and state governments have delayed their responses to the unforeseen seismic events, the issue has gained in prominence among researchers, affected community residents, and the media. This case study has offered a glimpse into the varied responses of stakeholders to human-induced seismicity in a small city in the state of Texas. It is evident from this case study that although individuals’ complaints and protests from a small community may not be successful in bringing about statewide changes in regulatory policies on disposal of fracking’s wastewater, they can add to the public pressure on the state government to do something to address the problem in a state that supports fracking.

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