Distinguishing Fluid Flow Path from Pore Pressure Diffusion for Induced Seismicity

2018 ◽  
Vol 108 (6) ◽  
pp. 3684-3686 ◽  
Author(s):  
Megan R. M. Brown ◽  
Shemin Ge
Keyword(s):  
Fluid Flow ◽  
Pore Pressure ◽  
Induced Seismicity ◽  
Flow Path ◽  
Pressure Diffusion

scholarly journals Pore-pressure diffusion, enhanced by poroelastic stresses, controls induced seismicity in Oklahoma

2019 ◽  
Vol 116 (33) ◽  
pp. 16228-16233 ◽  
Author(s):  
Guang Zhai ◽  
Manoochehr Shirzaei ◽  
Michael Manga ◽  
Xiaowei Chen
Keyword(s):  
Pore Pressure ◽  
Induced Seismicity ◽  
Energy Demand ◽  
Regional Scale ◽  
Exceedance Probability ◽  
Resource Exploitation ◽  
Induced Earthquakes ◽  
Seismicity Rate ◽  
Pressure Diffusion ◽  
Stress Changes

Induced seismicity linked to geothermal resource exploitation, hydraulic fracturing, and wastewater disposal is evolving into a global issue because of the increasing energy demand. Moderate to large induced earthquakes, causing widespread hazards, are often related to fluid injection into deep permeable formations that are hydraulically connected to the underlying crystalline basement. Using injection data combined with a physics-based linear poroelastic model and rate-and-state friction law, we compute the changes in crustal stress and seismicity rate in Oklahoma. This model can be used to assess earthquake potential on specific fault segments. The regional magnitude–time distribution of the observed magnitude (M) 3+ earthquakes during 2008–2017 is reproducible and is the same for the 2 optimal, conjugate fault orientations suggested for Oklahoma. At the regional scale, the timing of predicted seismicity rate, as opposed to its pattern and amplitude, is insensitive to hydrogeological and nucleation parameters in Oklahoma. Poroelastic stress changes alone have a small effect on the seismic hazard. However, their addition to pore-pressure changes can increase the seismicity rate by 6-fold and 2-fold for central and western Oklahoma, respectively. The injection-rate reduction in 2016 mitigates the exceedance probability of M5.0 by 22% in western Oklahoma, while that of central Oklahoma remains unchanged. A hypothetical injection shut-in in April 2017 causes the earthquake probability to approach its background level by ∼2025. We conclude that stress perturbation on prestressed faults due to pore-pressure diffusion, enhanced by poroelastic effects, is the primary driver of the induced earthquakes in Oklahoma.

New insights into the mechanisms of seismicity in the Azle area, North Texas

Geophysics ◽  
2019 ◽  
Vol 85 (1) ◽  
pp. EN1-EN15
Author(s):  
Rongqiang Chen ◽  
Xu Xue ◽  
Jaeyoung Park ◽  
Akhil Datta-Gupta ◽  
Michael J. King
Keyword(s):  
Fluid Flow ◽  
Stress Distribution ◽  
Pore Pressure ◽  
Induced Seismicity ◽  
Crystalline Basement ◽  
Water Volume ◽  
Optimization Approach ◽  
North Texas ◽  
Stress Changes ◽  
Area North

We have performed a site-specific study of the mechanics of induced seismicity in the Azle area, North Texas, using a coupled 3D fluid flow and poroelastic simulation model, extending from the overburden into the crystalline basement. The distinguishing feature of our study is that we account for the combined impact of water disposal injection and gas and water production on the pore pressure and stress distribution in this area. The model is calibrated using observed injection wellhead pressures and the location, timing, and magnitude of seismic events. We used a stochastic multiobjective optimization approach to obtain estimated ranges of fluid flow and poroelastic parameters, calibrated to the pressure, rate, and seismic event data. Mechanisms for induced seismicity were examined using these calibrated models. The calibrated models indicate no fluid movement or pressure increase in the crystalline basement, although there is plastic strain accumulation for the weaker elements along the fault in the basement. The accumulation of strain change appears to be caused by the unbalanced loading on different sides of the fault due to the differential in fluid injection and production. Previous studies ignored the produced gas volume, which is almost an order of magnitude larger than the produced water volume under reservoir conditions and which significantly impacts the pore pressure in the sedimentary formations and the stress distribution in the basement. A quantitative analysis indicates that the poroelastic stress changes dominate in the basement with no noticeable change in pore pressure. Even though the low-permeability faults in the basement are not in pressure communication with the Ellenburger formation, the poroelastic stresses transmitted to the basement can trigger seismicity without elevated pore pressure.

scholarly journals Seismicity at the Castor gas reservoir driven by pore pressure diffusion and asperities loading

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Simone Cesca ◽  
Daniel Stich ◽  
Francesco Grigoli ◽  
Alessandro Vuan ◽  
José Ángel López-Comino ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Induced Seismicity ◽  
Gas Injection ◽  
Oil Field ◽  
Underground Gas Storage ◽  
Gas Reservoir ◽  
Pressure Diffusion ◽  
Seismicity Catalog ◽  
Secondary Fault ◽  
Rupture Kinematics

AbstractThe 2013 seismic sequence at the Castor injection platform offshore Spain, including three earthquakes of magnitude 4.1, occurred during the initial filling of a planned Underground Gas Storage facility. The Castor sequence is one of the most important cases of induced seismicity in Europe and a rare example of seismicity induced by gas injection into a depleted oil field. Here we use advanced seismological techniques applied to an enhanced waveform dataset, to resolve the geometry of the faults, develop a greatly enlarged seismicity catalog and record details of the rupture kinematics. The sequence occurred by progressive fault failure and unlocking, with seismicity initially migrating away from the injection points, triggered by pore pressure diffusion, and then back again, breaking larger asperities loaded to higher stress and producing the largest earthquakes. Seismicity occurred almost exclusively on a secondary fault, located below the reservoir, dipping opposite from the reservoir bounding fault.

scholarly journals Analyzing the temporal fluctuations of the reservoir-triggered seismicity observed at Açu (Brazil)

2012 ◽  
Vol 12 (3) ◽  
pp. 805-811 ◽  
Author(s):  
L. Telesca ◽  
A. F. do Nascimento ◽  
F. H. R. Bezerra ◽  
J. M. Ferreira
Keyword(s):  
Pore Pressure ◽  
Time Scales ◽  
Strong Correlation ◽  
Induced Seismicity ◽  
Temporal Fluctuations ◽  
Time Dynamics ◽  
Reservoir Induced Seismicity ◽  
Physical Mechanisms ◽  
Triggered Seismicity ◽  
Pressure Diffusion

Abstract. The time dynamics of the reservoir-induced seismicity observed in Açu area (Brazil) from November 1994 to April 1997 reveals a super-Poissonian behaviour in the direction of a clustering process, where the occurrence of an earthquake increases the likelihood of the occurrence of a subsequent one. The seismicity shows strong correlation for time scales larger than approximately 1 day up to about four months, being characterized by Poissonian behavior for timescales smaller than 1 day. Processes of formation of fractures in the anisotropic and heterogeneous rockmass, along with pore pressure diffusion driven processes, are hypothesized as physical mechanisms for the appearance of Poissonian and clusterized dynamics respectively.

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