scholarly journals Slow slip-driven seismic signature triggered by water-reservoir impoundment

2021 ◽  
Author(s):  
Beata Orlecka-Sikora ◽  
Lukasz Rudzinski ◽  
Grzegorz Lizurek ◽  
Dorota Olszewska ◽  
Taghi Shirzad
Keyword(s):  
Pore Pressure ◽  
Earthquake Swarm ◽  
Water Reservoir ◽  
Slow Slip ◽  
Hydroelectric Energy ◽  
Physical Mechanisms ◽  
Triggered Seismicity ◽  
Reservoir Impoundment ◽  
Geological Conditions ◽  
Pressure Changes

Abstract One of the most important and widely used renewable energy sources is hydroelectric energy produced via Water Reservoir Impoundment (WRI). WRI can trigger strong earthquakes under favourable geological conditions. Thus, the socio-economic impact of reservoir triggered seismicity is very significant. Although many studies have investigated the relationship between the pore pressure changes due to WRI and the observed seismicity, hydromechanical models that explain the observed processes are rare. Here, we investigate the role of hydromechanical interactions during fault deformation to understand earthquake swarm bursts under pore pressure changes due to WRI. As a natural laboratory, we selected the Song Tranh 2 Reservoir in Vietnam. Because the analysed triggered seismicity has swarm characteristics, our work contributes to the further investigation of the physical mechanisms responsible for earthquake swarms and their relationship to slow slip. We conclude that the small high-frequency seismic swarms accompanying WRI are driven by slow slip along a fault; they occur due to the temperature-controlled frictional fault heterogeneity, and their rate and magnitude depend on the sizes of these heterogeneities. Swarm earthquakes are the effect of slip acceleration on the seismic radiation level. The nucleation fronts expand the nucleation regime and may transition into stronger earthquakes. These results provide insights into the physical mechanisms of seismic processes triggered by WRI, which may have implications for assessing the seismic hazards associated with hydroelectric energy production.

Seasonal trends of reservoir-triggered seismicity in Song Tranh 2 reservoir, Vietnam

2021 ◽  
Author(s):  
Grzegorz Lizurek ◽  
Konstantinos Leptokaropoulos ◽  
Jan Wiszniowski ◽  
Izabela Nowaczyńska ◽  
Nguyen Van Giang ◽  
...  
Keyword(s):  
Water Level ◽  
Pore Pressure ◽  
Seismic Activity ◽  
Water Level Fluctuations ◽  
Response Type ◽  
Seasonal Trends ◽  
Triggered Seismicity ◽  
Stress Orientation ◽  
Water Level Changes ◽  
Pressure Changes

<p>Reservoir-triggered seismicity (RTS) is the longest known anthropogenic seismicity type. It has the potential to generate seismic events of M6 and bigger. Previous studies of this phenomenon have proved that major events are triggered on preexisting major discontinuities, forced to slip by stress changes induced by water level fluctuations and/or pore-pressure changes in the rock mass in the vicinity of reservoirs. Song Tranh 2 is an artificial water reservoir located in Central Vietnam. Its main goal is back up the water for hydropower plant. High seismic activity has been observed in this area since the reservoir was first filled in 2011. The relation between water level and seismic activity in the Song Tranh area is complex, and the lack of clear correlation between water level and seismic activity has led to the conclusion that ongoing STR2 seismic activity is an example of the delayed response type of RTS. However, the first phase of the activity observed after impoundment has been deemed a rapid response type. In this work, we proved that the seismicity recorded between 2013 and 2016 manifested seasonal trends related to water level changes during wet and dry seasons. The response of activity and its delay with respect to water level changes suggest that the main triggering factor is pore pressure change due to the significant water level changes observed. A stress orientation difference between low and high water periods is also revealed. The findings indicate that water load and related pore pressure changes influence seismic activity and stress orientation in this area.</p><p>This work was partially supported by research project no. 2017/27/B/ST10/01267, funded by the National Science Centre, Poland, under agreement no. UMO-2017/27/B/ST10/01267.</p>

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.

Revisiting the Classical Experiment in Earthquake Control at the Rangely Oil Field, Colorado, 1970, Using a Coupled Flow and Geomechanical Model

2021 ◽  
Author(s):  
Josimar A. Silva ◽  
Hannah Byrne ◽  
Andreas Plesch ◽  
John H. Shaw ◽  
Ruben Juanes
Keyword(s):  
Pore Pressure ◽  
Oil Field ◽  
Coupled Flow ◽  
Injection Wells ◽  
Rock Types ◽  
Pressure Diffusion ◽  
Main Fault ◽  
Injection Interval ◽  
Using Data ◽  
Pressure Changes

ABSTRACT The injection experiment conducted at the Rangely oil field, Colorado, was a pioneering study that showed qualitatively the correlation between reservoir pressure increases and earthquake occurrence. Here, we revisit this field experiment using a mechanistic approach to investigate why and how the earthquakes occurred. Using data collected from decades of field operations, we build a geological model for the Rangely oil field, perform reservoir simulation to history match pore-pressure variations during the experiment, and perform geomechanical simulations to obtain stresses at the main fault, where the earthquakes were sourced. As a viable model, we hypothesize that pressure diffusion occurred through a system of highly permeable fractures, adjacent to the main fault in the field, connecting the injection wells to the area outside of the injection interval where intense seismic activity occurred. We also find that the main fault in the field is characterized by a friction coefficient μ  ≈  0.7—a value that is in good agreement with the classical laboratory estimates conducted by Byerlee for a variety of rock types. Finally, our modeling results suggest that earthquakes outside of the injection interval were released tectonic stresses and thus should be classified as triggered, whereas earthquakes inside the injection interval were driven mostly by anthropogenic pore-pressure changes and thus should be classified as induced.

The role of geomechanical modeling in the measurement and understanding of geophysical data collected during carbon sequestration

2021 ◽  
Vol 40 (6) ◽  
pp. 413-417
Author(s):  
Chunfang Meng ◽  
Michael Fehler
Keyword(s):  
Pore Pressure ◽  
Fault Location ◽  
Mechanical Response ◽  
Fluid Pressure ◽  
Geophysical Data ◽  
Fluid Injection ◽  
Coupled Flow ◽  
Cap Rock ◽  
Stress And Deformation ◽  
Pressure Changes

As fluids are injected into a reservoir, the pore fluid pressure changes in space and time. These changes induce a mechanical response to the reservoir fractures, which in turn induces changes in stress and deformation to the surrounding rock. The changes in stress and associated deformation comprise the geomechanical response of the reservoir to the injection. This response can result in slip along faults and potentially the loss of fluid containment within a reservoir as a result of cap-rock failure. It is important to recognize that the slip along faults does not occur only due to the changes in pore pressure at the fault location; it can also be a response to poroelastic changes in stress located away from the region where pore pressure itself changes. Our goal here is to briefly describe some of the concepts of geomechanics and the coupled flow-geomechanical response of the reservoir to fluid injection. We will illustrate some of the concepts with modeling examples that help build our intuition for understanding and predicting possible responses of reservoirs to injection. It is essential to understand and apply these concepts to properly use geomechanical modeling to design geophysical acquisition geometries and to properly interpret the geophysical data acquired during fluid injection.

Interpreting pore-water pressure changes induced by water table fluctuations and mechanical loading due to soil moisture changes

2012 ◽  
Vol 49 (3) ◽  
pp. 357-366 ◽  
Author(s):  
Collins Ifeanyichukwu Anochikwa ◽  
Garth van der Kamp ◽  
S. Lee Barbour
Keyword(s):  
Soil Moisture ◽  
Pore Pressure ◽  
Mechanical Loading ◽  
Water Table ◽  
Pressure Response ◽  
Stress Strain ◽  
Near Surface ◽  
Water Table Fluctuations ◽  
Pore Pressure Response ◽  
Pressure Changes

Pore pressures within saturated subsurface formations respond to stress changes due to loading as well as to changes in pore pressure at the boundaries of the formation. The pore-pressure dynamics within a thick aquitard in response to water table fluctuations and mechanical loading due to soil moisture changes have been simulated using a coupled stress–strain and groundwater flow finite element formulation. This modelling approach isolates the component of pore-pressure response of soil moisture loading from that caused by water table fluctuations, by using a method of superposition. In this manner, the contributions to pore-pressure fluctuations that occur as a result of surface moisture loading (e.g., precipitation, evapotranspiration) can be isolated from the pore-pressure record. The required elastic stress–strain properties of the aquitard were obtained from the measured pore-pressure response to barometric pressure changes. Subsequently, the numerical simulations could be calibrated to the measured response by adjusting only the hydraulic conductivity. This paper highlights the significance of moisture loading effects in pore-pressure observations and describes an efficient technique for obtaining in situ stress–strain and hydraulic properties of near-surface aquitards.

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