scholarly journals 3-D mechanical analysis of complex reservoirs: a novel mesh-free approach

2019 ◽  
Vol 219 (2) ◽  
pp. 1118-1130
Author(s):  
Jan-Diederik van Wees ◽  
Maarten Pluymaekers ◽  
Sander Osinga ◽  
Peter Fokker ◽  
Karin Van Thienen-Visser ◽  
...  
Keyword(s):  
Seismic Moment ◽  
Induced Seismicity ◽  
Mechanical Analysis ◽  
Fault System ◽  
Multiple Faults ◽  
Computational Performance ◽  
Induced Stress ◽  
Mesh Free ◽  
Stress Changes ◽  
Octree Representation

SUMMARY Building geomechanical models for induced seismicity in complex reservoirs poses a major challenge, in particular if many faults need to be included. We developed a novel way of calculating induced stress changes and associated seismic moment response for structurally complex reservoirs with tens to hundreds of faults. Our specific target was to improve the predictive capability of stress evolution along multiple faults, and to use the calculations to enhance physics-based understanding of the reservoir seismicity. Our methodology deploys a mesh-free numerical and analytical approach for both the stress calculation and the seismic moment calculation. We introduce a high-performance computational method for high-resolution induced Coulomb stress changes along faults, based on a Green's function for the stress response to a nucleus of strain. One key ingredient is the deployment of an octree representation and calculation scheme for the nuclei of strain, based on the topology and spatial variability of the mesh of the reservoir flow model. Once the induced stress changes are evaluated along multiple faults, we calculate potential seismic moment release in a fault system supposing an initial stress field. The capability of the approach, dubbed as MACRIS (Mechanical Analysis of Complex Reservoirs for Induced Seismicity) is proven through comparisons with finite element models. Computational performance and suitability for probabilistic assessment of seismic hazards are demonstrated though the use of the complex, heavily faulted Gullfaks field.

scholarly journals Geomechanical models for induced seismicity in the Netherlands: inferences from simplified analytical, finite element and rupture model approaches

2017 ◽  
Vol 96 (5) ◽  
pp. s183-s202 ◽  
Author(s):  
Jan-Diederik Van Wees ◽  
Peter A. Fokker ◽  
Karin Van Thienen-Visser ◽  
Brecht B.T. Wassing ◽  
Sander Osinga ◽  
...  
Keyword(s):  
The Netherlands ◽  
Seismic Moment ◽  
Induced Seismicity ◽  
Central Area ◽  
Pressure Change ◽  
Seismicity Rates ◽  
Stress Changes ◽  
Pressure Depletion ◽  
Rupture Model ◽  
Gas Fields

AbstractIn the Netherlands, over 190 gas fields of varying size have been exploited, and 15% of these have shown seismicity. The prime cause for seismicity due to gas depletion is stress changes caused by pressure depletion and by differential compaction. The observed onset of induced seismicity due to gas depletion in the Netherlands occurs after a considerable pressure drop in the gas fields. Geomechanical studies show that both the delay in the onset of induced seismicity and the nonlinear increase in seismic moment observed for the induced seismicity in the Groningen field can be explained by a model of pressure depletion, if the faults causing the induced seismicity are not critically stressed at the onset of depletion. Our model shows concave patterns of log moment with time for individual faults. This suggests that the growth of future seismicity could well be more limited than would be inferred from extrapolation of the observed trend between production or compaction and seismicity. The geomechanical models predict that seismic moment increase should slow down significantly immediately after a production decrease, independently of the decay rate of the compaction model. These findings are in agreement with the observed reduced seismicity rates in the central area of the Groningen field immediately after production decrease on 17 January 2014. The geomechanical model findings therefore support scope for mitigating induced seismicity by adjusting rates of production and associated pressure change. These simplified models cannot serve as comprehensive models for predicting induced seismicity in any particular field. To this end, a more detailed field-specific study, taking into account the full complexity of reservoir geometry, depletion history and mechanical properties, is required.

scholarly journals Methodology for Earthquake Rupture Rate estimates of fault networks: example for the Western Corinth Rift, Greece

2017 ◽  
Author(s):  
Thomas Chartier ◽  
Oona Scotti ◽  
Hélène Lyon-Caen ◽  
Aurélien Boiselet
Keyword(s):  
Active Faults ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
System Level ◽  
Fault System ◽  
Normal Faults ◽  
Accurate Estimation ◽  
Probabilistic Seismic Hazard Assessment ◽  
Earthquake Rupture ◽  
Multiple Faults

Abstract. Modelling the seismic potential of active faults is a fundamental step of probabilistic seismic hazard assessment (PSHA). An accurate estimation of the rate of earthquakes on the faults is necessary in order to obtain the probability of exceedance of a given ground motion. Most PSHA studies consider faults as independent structures and neglect the possibility of multiple faults or fault segments rupturing simultaneously (Fault to Fault -FtF- ruptures). The latest Californian model (UCERF-3) takes into account this possibility by considering a system level approach rather than an individual fault level approach using the geological , seismological and geodetical information to invert the earthquake rates. In many places of the world seismological and geodetical information long fault networks are often not well constrained. There is therefore a need to propose a methodology relying only on geological information to compute earthquake rate of the faults in the network. In this methodology, similarly to UCERF-3, a simple distance criteria is used to define FtF ruptures and consider single faults or FtF ruptures as an aleatory uncertainty. Rates of earthquakes on faults are then computed following two constraints: the magnitude frequency distribution (MFD) of earthquakes in the fault system as a whole must follow an imposed shape and the rate of earthquakes on each fault is determined by the specific slip-rate of each segment depending on the possible FtF ruptures. The modelled earthquake rates are then confronted to the available independent data (geodetical, seismological and paleoseismological data) in order to weigh different hypothesis explored in a logic tree. The methodology is tested on the Western Corinth Rift, Greece (WCR) where recent advancements have been made in the understanding of the geological slip rates of the complex network of normal faults which are accommodating the ~15 mm/yr North-South extension. Modelling results show that geological, seismological extension rates and paleoseismological rates of earthquakes cannot be reconciled with only single fault rupture scenarios and require hypothesising a large spectrum of possible FtF rupture sets. Furthermore, in order to fit the imposed regional Gutenberg-Richter MFD target, some of the slip along certain faults needs to be accommodated either with interseismic creep or as post-seismic processes. Furthermore, individual fault’s MFDs differ depending on the position of each fault in the system and the possible FtF ruptures associated with the fault. Finally, a comparison of modelled earthquake rupture rates with those deduced from the regional and local earthquake catalogue statistics and local paleosismological data indicates a better fit with the FtF rupture set constructed with a distance criteria based on a 5 km rather than 3 km, suggesting, a high connectivity of faults in the WCR fault system.

scholarly journals Injection‐Induced Seismic Moment Release and Laboratory Fault Slip: Implications for Fluid‐Induced Seismicity

2020 ◽  
Vol 47 (22) ◽  
Author(s):  
Lei Wang ◽  
Grzegorz Kwiatek ◽  
Erik Rybacki ◽  
Marco Bohnhoff ◽  
Georg Dresen
Keyword(s):  
Seismic Moment ◽  
Induced Seismicity ◽  
Fault Slip ◽  
Seismic Moment Release

scholarly journals Induced seismicity in geologic carbon storage

Solid Earth ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 871-892 ◽  
Author(s):  
Víctor Vilarrasa ◽  
Jesus Carrera ◽  
Sebastià Olivella ◽  
Jonny Rutqvist ◽  
Lyesse Laloui
Keyword(s):  
Carbon Storage ◽  
Induced Seismicity ◽  
Public Perception ◽  
Fault Reactivation ◽  
Wellbore Stability ◽  
Rock Properties ◽  
Geologic Carbon Storage ◽  
Stress Changes ◽  
The Impact ◽  
Injection Formation

Abstract. Geologic carbon storage, as well as other geo-energy applications, such as geothermal energy, seasonal natural gas storage and subsurface energy storage imply fluid injection and/or extraction that causes changes in rock stress field and may induce (micro)seismicity. If felt, seismicity has a negative effect on public perception and may jeopardize wellbore stability and damage infrastructure. Thus, induced earthquakes should be minimized to successfully deploy geo-energies. However, numerous processes may trigger induced seismicity, which contribute to making it complex and translates into a limited forecast ability of current predictive models. We review the triggering mechanisms of induced seismicity. Specifically, we analyze (1) the impact of pore pressure evolution and the effect that properties of the injected fluid have on fracture and/or fault stability; (2) non-isothermal effects caused by the fact that the injected fluid usually reaches the injection formation at a lower temperature than that of the rock, inducing rock contraction, thermal stress reduction and stress redistribution around the cooled region; (3) local stress changes induced when low-permeability faults cross the injection formation, which may reduce their stability and eventually cause fault reactivation; (4) stress transfer caused by seismic or aseismic slip; and (5) geochemical effects, which may be especially relevant in carbonate-containing formations. We also review characterization techniques developed by the authors to reduce the uncertainty in rock properties and subsurface heterogeneity both for the screening of injection sites and for the operation of projects. Based on the review, we propose a methodology based on proper site characterization, monitoring and pressure management to minimize induced seismicity.

Investigation of Dynamic and Static Effects on Earthquake Triggering Using Different Rate and State Friction Laws and Marmara Simulation

2020 ◽  
Author(s):  
Eyup Sopaci ◽  
Atilla Arda Özacar
Keyword(s):  
Onset Time ◽  
Static Stress ◽  
Fault System ◽  
Dynamic Effects ◽  
Earthquake Triggering ◽  
Dynamic Changes ◽  
System Parameters ◽  
Fault Segment ◽  
Stress Changes ◽  
Rate And State Friction

<p>The clock of an earthquake can be advanced due to dynamic and static changes when a triggering signal is applied to a stress-loading fault. While static effects decrease rapidly with distance, dynamic effects can reach thousands of kilometers away. Therefore, earthquake triggering is traditionally associated to static stress changes at local distances and to dynamic effects at greater scales. However, static and dynamic effects near the triggering signal are often nested, thus identifying which effect dominates, becomes unclear. So far, earthquake triggering has been tested using different rate-and-state friction (RSF) laws utilizing alternative views of friction without much comparison. In this study, the analogy of an earthquake is simulated using single degree of freedom spring-block systems governed with three different RSF laws, namely “Dieterich”, “Ruina” and “Perrin”. First, the fault systems are evolved until they reach a stable limit cycle and then static, dynamic and their combination are applied as triggering signals. During synthetic simulations, effects of the triggering signal parameters (onset time, size, duration and frequency) and the fault system parameters (fault stiffness, characteristic slip distance, direct velocity and time dependent state effects) are tested separately. Our results indicate that earthquake triggering is controlled mainly by the onset time, size and duration of the triggering signal but not much sensitive to the signal frequency. In terms of fault system parameters, the fault stiffness and the direct velocity effect are the critical parameters in triggering processes. Among the tested RSF laws, “Ruina” law is more sensitive than “Dieterich” law to both static and dynamic changes and “Perrin” is apparently the most sensitive law to dynamic changes. Especially, when the triggering onset time is close to an unperturbed failure time (future earthquake), dynamic changes result the largest clock advancement, otherwise, static stress changes are substantially more effective. In the next step, realistic models will be established to simulate the effect of the recent (26 September 2019) Marmara earthquake with Mw=5.7 on the locked Kumburgaz fault segment of the North Anatolian Fault Zone. The triggering earthquake will be simulated by combining the static stress change computed via Coulomb law and the dynamic effects using ground motions recorded at broadband seismic stations within similar distances. Outcomes will help us to better understand the effects of static and dynamic changes on the seismic cycle of the Kumburgaz fault segment, which is expected to break soon with a possibly big earthquake causing damage at the metropolitan area of Istanbul in Turkey.</p>

A note on induced stress changes in hydrocarbon and geothermal reservoirs

1998 ◽  
Vol 289 (1-3) ◽  
pp. 117-128 ◽  
Author(s):  
Paul Segall ◽  
Shaun D. Fitzgerald
Keyword(s):  
Geothermal Reservoirs ◽  
Induced Stress ◽  
Stress Changes

Origin of MeV ion irradiation-induced stress changes in SiO2

2000 ◽  
Vol 88 (1) ◽  
pp. 59-64 ◽  
Author(s):  
M. L. Brongersma ◽  
E. Snoeks ◽  
T. van Dillen ◽  
A. Polman
Keyword(s):  
Ion Irradiation ◽  
Induced Stress ◽  
Stress Changes

scholarly journals Predator-induced stress changes parental feeding behavior in pied flycatchers

2010 ◽  
Vol 22 (1) ◽  
pp. 23-28 ◽  
Author(s):  
Vallo Tilgar ◽  
Kadri Moks ◽  
Pauli Saag
Keyword(s):  
Feeding Behavior ◽  
Induced Stress ◽  
Parental Feeding ◽  
Stress Changes

scholarly journals Development of Characterization Technology for Fault Zone Hydrology

2010 ◽  
Author(s):  
Kenzi Karasaki ◽  
Celia Tiemi Onishi ◽  
Erika Gasperikova ◽  
Junichi Goto ◽  
Hiroyuki Tsuchi ◽  
...  
Keyword(s):  
Fault Zone ◽  
Fault System ◽  
Hydraulic Test ◽  
Multiple Faults ◽  
Geophysical Surveys ◽  
Geophysical Logs ◽  
Main Fault ◽  
Unexpected Findings ◽  
Fracture Scale ◽  
Long Term Behavior

Several deep trenches were cut, and a number of geophysical surveys were conducted across the Wildcat Fault in the hills east of Berkeley, California. The Wildcat Fault is believed to be a strike-slip fault and a member of the Hayward Fault System, with over 10 km of displacement. So far, three boreholes of ∼ 150m deep have been core-drilled and borehole geophysical logs were conducted. The rocks are extensively sheared and fractured; gouges were observed at several depths and a thick cataclasitic zone was also observed. While confirming some earlier, published conclusions from shallow observations about Wildcat, some unexpected findings were encountered. Preliminary analysis indicates that Wildcat near the field site consists of multiple faults. The hydraulic test data suggest the dual properties of the hydrologic structure of the fault zone. A fourth borehole is planned to penetrate the main fault believed to lie in-between the holes. The main philosophy behind our approach for the hydrologic characterization of such a complex fractured system is to let the system take its own average and monitor a long term behavior instead of collecting a multitude of data at small length and time scales, or at a discrete fracture scale and to “up-scale,” which is extremely tenuous.

scholarly journals Evolution of Seismicity During a Stalled Episode of Reawakening at Cayambe Volcano, Ecuador

2021 ◽  
Vol 9 ◽  
Author(s):  
S. Butcher ◽  
A. F. Bell ◽  
S. Hernandez ◽  
M. Ruiz
Keyword(s):  
Template Matching ◽  
Monitoring Network ◽  
Fault System ◽  
Magma Ascent ◽  
Volcanic Complex ◽  
Agricultural Industry ◽  
Complex Interactions ◽  
Stress Changes ◽  
Distinct Source ◽  
Regional Tectonic

Cayambe Volcano is an ice-capped, 5,790 m high, andesitic-dacitic volcanic complex, located on the equator in the Eastern Cordillera of the Ecuadorian Andes. An eruption at Cayambe would pose considerable hazards to surrounding communities and a nationally significant agricultural industry. Although the only historically documented eruption was in 1785, it remains persistently restless and long-period (LP) seismicity has been consistently observed at the volcano for over 10 years. However, the sparse monitoring network, and complex interactions between the magmatic, hydrothermal, glacial, and tectonic systems, make unrest at Cayambe challenging to interpret. In June 2016 a seismic “crisis” began at Cayambe, as rates of high frequency volcano-tectonic (VT) earthquakes increased to hundreds of events per day, leading to speculation about the possibility of a forthcoming eruption. The crisis began 2 months after the Mw7.8 Pedernales earthquake, which occurred on the coast, 200 km from Cayambe. Here we show that the 2016 seismicity at Cayambe resulted from four distinct source processes. Cross correlation, template matching, and spectral analysis isolate two source regions for VT earthquakes–tectonic events from a regional fault system and more varied VTs from beneath the volcanic cone. The temporal evolution of the LP seismicity, and mean Q value of 9.9, indicate that these events are most likely generated by flow of hydrothermal fluids. These observations are consistent with a model where a new pulse of magma ascent initially stresses regional tectonic faults, and subsequently drives elevated VT seismicity in the edifice. We draw comparisons from models of volcano-tectonic interactions, and speculate that static stress changes from the Pedernales earthquake put Cayambe volcano in an area of dilation, providing a mechanism for magma ascent. Our findings provide a better understanding of “background” seismicity at Cayambe allowing faster characterization of future crises, and a benchmark to measure changes driven by rapid glacial retreat.

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