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

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.

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

10.5194/egusphere-egu2020-10905 ◽

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>

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

Geophysical Journal International ◽

10.1093/gji/ggz352 ◽

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.

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Production induced subsidence and seismicity in the Groningen gas field – can it be managed?

Proceedings of the International Association of Hydrological Sciences ◽

10.5194/piahs-372-129-2015 ◽

2015 ◽

Vol 372 ◽

pp. 129-139 ◽

Cited By ~ 14

Author(s):

J. A. de Waal ◽

A. G. Muntendam-Bos ◽

J. P. A. Roest

Keyword(s):

Water Management ◽

The Netherlands ◽

Sea Level ◽

Induced Seismicity ◽

Seismic Risk ◽

Central Area ◽

Gas Production ◽

Mitigation Measures ◽

Subsidence Rate ◽

Subsidence Prediction

Abstract. Reliable prediction of the induced subsidence resulting from gas production is important for a near sea level country like the Netherlands. Without the protection of dunes, dikes and pumping, large parts of the country would be flooded. The predicted sea-level rise from global warming increases the challenge to design proper mitigation measures. Water management problems from gas production induced subsidence can be prevented if measures to counter its adverse effects are taken timely. This requires reliable subsidence predictions, which is a major challenge. Since the 1960's a number of large, multi-decade gas production projects were started in the Netherlands. Extensive, well-documented subsidence prediction and monitoring technologies were applied. Nevertheless predicted subsidence at the end of the Groningen field production period (for the centre of the bowl) went from 100 cm in 1971 to 77 cm in 1973 and then to 30 cm in 1977. In 1984 the prediction went up again to 65 cm, down to 36 cm in 1990 and then via 38 cm (1995) and 42 cm (2005) to 47 cm in 2010 and 49 cm in 2013. Such changes can have large implications for the planning of water management measures. Until 1991, when the first event was registered, production induced seismicity was not observed nor expected for the Groningen field. Thereafter the number of observed events rose from 5 to 10 per year during the 1990's to well over a hundred in 2013. The anticipated maximum likely magnitude rose from an initial value of less than 3.0 to a value of 3.3 in 1993 and then to 3.9 in 2006. The strongest tremor to date occurred near the village of Huizinge in August 2012. It had a magnitude of 3.6, caused significant damage and triggered the regulator into an independent investigation. Late 2012 it became clear that significantly larger magnitudes cannot be excluded and that values up to magnitude 5.0 cannot be ruled out. As a consequence the regulator advised early 2013 to lower Groningen gas production by as much and as fast as realistically possible. Before taking such a decision, the Minister of Economic Affairs requested further studies. The results became available early 2014 and led to the government decision to lower gas production in the earthquake prone central area of the field by 80 % for the next three~years. In addition further investigations and a program to strengthen houses and infrastructure were started. Important lessons have been learned from the studies carried out to date. It is now realised that uncertainties in predicted subsidence and seismicity are much larger than previously recognised. Compaction, subsidence and seismicity are strongly interlinked and relate in a non-linear way to production and pressure drop. The latest studies by the operator suggest that seismic hazard in Groningen is largely determined by tremors with magnitudes between 4.5 and 5.0 even at an annual probability of occurrence of less than 1 %. And that subsidence in 2080 in the centre of the bowl could be anywhere between 50 and 70 cm. Initial evaluations by the regulator indicate similar numbers and suggest that the present seismic risk is comparable to Dutch flooding risks. Different models and parameters can be used to describe the subsidence and seismicity observed so far. The choice of compaction and seismicity models and their parameters has a large impact on the calculated future subsidence (rates), seismic activity and on the predicted response to changes in gas production. In addition there are considerable uncertainties in the ground motions resulting from an earthquake of a given magnitude and in the expected response of buildings and infrastructure. As a result uncertainties in subsidence and seismicity become very large for periods more than three to five years into the future. To counter this a control loop based on interactive modelling, measurements and repeated calibration will be used. Over the coming years, the effect of the production reduction in the centre of the field on subsidence and seismicity will be studied in detail in an effort to improve understanding and thereby reduce prediction uncertainties. First indications are that the reduction has led to a drop in subsidence rate and seismicity within a period of a few months. This suggests that the system can be controlled and regulated. If this is the case, the integrated loop of predicting, monitoring and updating in combination with mitigation measures can be applied to keep subsidence (rate) and induced seismicity within limits. To be able to do so, the operator has extended the field-monitoring network. It now includes PS-InSAR and GPS stations for semi-permanent subsidence monitoring in addition to a traditional network of levelling benchmarks. For the seismic monitoring 60 shallow (200 m) borehole seismometers, 60 + accelerometers and two permanent downhole seismic arrays at reservoir level will be added. Scenario's spanning the range of parameter and model uncertainties will be generated to calculate possible subsidence and seismicity outcomes. The probability of each scenario will be updated over time through confrontation with the measurements as they become available. At regular intervals the subsidence prediction and the seismic risk will be re-evaluated. Further mitigation measures, possibly including further production measures will need to be taken if probabilities indicate unacceptable risks.

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Stress Drop, Seismogenic Index and Fault Cohesion of Fluid-Induced Earthquakes

Rock Mechanics and Rock Engineering ◽

10.1007/s00603-021-02420-3 ◽

2021 ◽

Author(s):

Serge A. Shapiro ◽

Carsten Dinske

Keyword(s):

Stress Drop ◽

Induced Seismicity ◽

Quantitative Characteristic ◽

High Stress ◽

Operation Time ◽

Average Stress ◽

Induced Earthquakes ◽

Effective Stresses ◽

Seismicity Rates

AbstractSometimes, a rather high stress drop characterizes earthquakes induced by underground fluid injections or productions. In addition, long-term fluid operations in the underground can influence a seismogenic reaction of the rock per unit volume of the fluid involved. The seismogenic index is a quantitative characteristic of such a reaction. We derive a relationship between the seismogenic index and stress drop. This relationship shows that the seismogenic index increases with the average stress drop of induced seismicity. Further, we formulate a simple and rather general phenomenological model of stress drop of induced earthquakes. This model shows that both a decrease of fault cohesion during the earthquake rupture process and an enhanced level of effective stresses could lead to high stress drop. Using these two formulations, we propose the following mechanism of increasing induced seismicity rates observed, e.g., by long-term gas production at Groningen. Pore pressure depletion can lead to a systematic increase of the average stress drop (and thus, of magnitudes) due to gradually destabilizing cohesive faults and due to a general increase of effective stresses. Consequently, elevated average stress drop increases seismogenic index. This can lead to seismic risk increasing with the operation time of an underground reservoir.

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Managing Mature Gas Fields in the Netherlands - Future Outlook

10.2118/166627-ms ◽

2013 ◽

Author(s):

Ferhat Yavuz ◽

Eric Kreft ◽

Maximiliaan R Gijbels

Keyword(s):

The Netherlands ◽

Future Outlook ◽

Gas Fields

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Experimental and Modeling Study of Salt Precipitation During Injection of CO2 Contaminated With H2S Into Depleted Gas Fields in the Northeast of the Netherlands

SPE Journal ◽

10.2118/164932-pa ◽

2014 ◽

Vol 19 (06) ◽

pp. 1058-1068 ◽

Cited By ~ 9

Author(s):

P.. Bolourinejad ◽

R.. Herber

Keyword(s):

The Netherlands ◽

Carbonic Acid ◽

Co2 Storage ◽

Mineral Dissolution ◽

Co2 Injection ◽

Salt Precipitation ◽

Geological Time ◽

Core Samples ◽

Carbon Dioxide Co2 ◽

Gas Fields

Summary Depleted gas fields are among the most probable candidates for subsurface storage of carbon dioxide (CO2). With proven reservoir and qualified seal, these fields have retained gas over geological time scales. However, unlike methane, injection of CO2 changes the pH of the brine because of the formation of carbonic acid. Subsequent dissolution/precipitation of minerals changes the porosity/permeability of reservoir and caprock. Thus, for adequate, safe, and effective CO2 storage, the subsurface system needs to be fully understood. An important aspect for subsurface storage of CO2 is purity of this gas, which influences risk and cost of the process. To investigate the effects of CO2 plus impurities in a real case example, we have carried out medium-term (30-day) laboratory experiments (300 bar, 100°C) on reservoir and caprock core samples from gas fields in the northeast of the Netherlands. In addition, we attempted to determine the maximum allowable concentration of one of the possible impurities in the CO2 stream [hydrogen sulfide (H2S)] in these fields. The injected gases—CO2, CO2+100 ppm H2S, and CO2+5,000 ppm H2S—were reacting with core samples and brine (81 g/L Na+, 173 g/L Cl−, 22 g/L Ca2+, 23 g/L Mg2+, 1.5 g/L K+, and 0.2 g/L SO42−). Before and after the experiments, the core samples were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD) for mineralogical variations. The permeability of the samples was also measured. After the experiments, dissolution of feldspars, carbonates, and kaolinite was observed as expected. In addition, we observed fresh precipitation of kaolinite. However, two significant results were obtained when adding H2S to the CO2 stream. First, we observed precipitation of sulfate minerals (anhydrite and pyrite). This differs from results after pure CO2 injection, where dissolution of anhydrite was dominant in the samples. Second, severe salt precipitation took place in the presence of H2S. This is mainly caused by the nucleation of anhydrite and pyrite, which enabled halite precipitation, and to a lesser degree by the higher solubility of H2S in water and higher water content of the gas phase in the presence of H2S. This was confirmed by the use of CMG-GEM (CMG 2011) modeling software. The precipitation of halite, anhydrite, and pyrite affects the permeability of the samples in different ways. After pure CO2 and CO2+100 ppm H2S injection, permeability of the reservoir samples increased by 10–30% and ≤3%, respectively. In caprock samples, permeability increased by a factor of 3–10 and 1.3, respectively. However, after addition of 5,000 ppm H2S, the permeability of all samples decreased significantly. In the case of CO2+100 ppm H2S, halite, anhydrite, and pyrite precipitation did balance mineral dissolution, causing minimal variation in the permeability of samples.

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Seismic moment catalog of large shallow earthquakes, 1900 to 1989

Bulletin of the Seismological Society of America ◽

10.1785/bssa0820031306 ◽

1992 ◽

Vol 82 (3) ◽

pp. 1306-1349 ◽

Cited By ~ 2

Author(s):

Javier F. Pacheco ◽

Lynn R. Sykes

Keyword(s):

Seismic Moment ◽

Subduction Zones ◽

B Value ◽

Reference List ◽

Transform Faults ◽

Shallow Earthquakes ◽

Seismicity Rates ◽

Chile Earthquake ◽

The Moment ◽

Earthquake Process

Abstract We compile a worldwide catalog of shallow (depth < 70 km) and large (Ms ≥ 7) earthquakes recorded between 1900 and 1989. The catalog is shown to be complete and uniform at the 20-sec surface-wave magnitude Ms ≥ 7.0. We base our catalog on those of Abe (1981, 1984) and Abe and Noguchi (1983a, b) for events with Ms ≥ 7.0. Those catalogs, however, are not homogeneous in seismicity rates for the entire 90-year period. We assume that global rates of seismicity are constant on a time scale of decades and most inhomogeneities arise from changes in instrumentation and/or reporting. We correct the magnitudes to produce a homogeneous catalog. The catalog is accompanied by a reference list for all the events with seismic moment determined at periods longer than 20 sec. Using these seismic moments for great and giant earthquakes and a moment-magnitude relationship for smaller events, we produce a seismic moment catalog for large earthquakes from 1900 to 1989. The catalog is used to study the distribution of moment released worldwide. Although we assumed a constant rate of seismicity on a global basis, the rate of moment release has not been constant for the 90-year period because the latter is dominated by the few largest earthquakes. We find that the seismic moment released at subduction zones during this century constitutes 90% of all the moment released by large, shallow earthquakes on a global basis. The seismic moment released in the largest event that occurred during this century, the 1960 southern Chile earthquake, represents about 30 to 45% of the total moment released from 1900 through 1989. A frequency-size distribution of earthquakes with seismic moment yields an average slope (b value) that changes from 1.04 for magnitudes between 7.0 and 7.5 to b = 1.51 for magnitudes between 7.6 and 8.0. This change in the b value is attributed to different scaling relationships between bounded (large) and unbounded (small) earthquakes. Thus, the earthquake process does have a characteristic length scale that is set by the downdip width over which rupture in earthquakes can occur. That width is typically greater for thrust events at subduction zones than for earthquakes along transform faults and other tectonic environments.

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Fluid-induced aseismic fault slip outpaces pore-fluid migration

Science ◽

10.1126/science.aaw7354 ◽

2019 ◽

Vol 364 (6439) ◽

pp. 464-468 ◽

Cited By ~ 36

Author(s):

Pathikrit Bhattacharya ◽

Robert C. Viesca

Keyword(s):

Pore Fluid ◽

Fluid Injection ◽

Fluid Migration ◽

Aseismic Slip ◽

Earthquake Triggering ◽

Effective Normal Stress ◽

Shear Rupture ◽

Stress Changes ◽

Slip History ◽

Rupture Model

Earthquake swarms attributed to subsurface fluid injection are usually assumed to occur on faults destabilized by increased pore-fluid pressures. However, fluid injection could also activate aseismic slip, which might outpace pore-fluid migration and transmit earthquake-triggering stress changes beyond the fluid-pressurized region. We tested this theoretical prediction against data derived from fluid-injection experiments that activated and measured slow, aseismic slip on preexisting, shallow faults. We found that the pore pressure and slip history imply a fault whose strength is the product of a slip-weakening friction coefficient and the local effective normal stress. Using a coupled shear-rupture model, we derived constraints on the hydromechanical parameters of the actively deforming fault. The inferred aseismic rupture front propagates faster and to larger distances than the diffusion of pressurized pore fluid.

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