Reply to “Comment on ‘The Maximum Possible and the Maximum Expected Earthquake Magnitude for Production‐Induced Earthquakes at the Gas Field in Groningen, The Netherlands’ by Gert Zöller and Matthias Holschneider” by Mathias Raschke

2018 ◽  
Vol 108 (2) ◽  
pp. 1029-1030 ◽  
Author(s):  
Gert Zöller ◽  
Matthias Holschneider
2017 ◽  
Vol 96 (5) ◽  
pp. s27-s38 ◽  
Author(s):  
Danijela Sijacic ◽  
Frank Pijpers ◽  
Manuel Nepveu ◽  
Karin van Thienen-Visser

AbstractDepletion of the Groningen gas field has induced earthquakes, although the north of the Netherlands is a tectonically inactive region. Increased seismic activity raised public concern which led the government to initiate a number of studies with the aim of understanding the cause(s) of the earthquakes. If the relationship between production and seismicity were understood then production could be optimized in such a way that the risk of induced seismicity would be minimal. The main question remains how production is correlated with induced seismicity. The Minister of Economic Affairs of the Netherlands decided to reduce production starting from 17 January 2014, specifically in the centre of the gas field as it has the highest rates of seismicity, the largest-magnitude events and the highest compaction values of the field.A reduction in production could possibly lead to a reduced rate of compaction. Additionally a reduction of production rate could lead to a reduced stress rate increase on the existing faults and consequently fewer seismic events per year. One might envisage a ‘bonus effect’ in the events reduction in the sense that the total number of events will be less, with the same total production smeared out over a longer period. This is as yet unclear.In this paper we apply different statistical methods to look for evidence supporting or disproving a decrease in the number of seismic events due to production reduction.


2017 ◽  
Vol 33 (2) ◽  
pp. 481-498 ◽  
Author(s):  
Julian J. Bommer ◽  
Peter J. Stafford ◽  
Benjamin Edwards ◽  
Bernard Dost ◽  
Ewoud van Dedem ◽  
...  

The potential for building damage and personal injury due to induced earthquakes in the Groningen gas field is being modeled in order to inform risk management decisions. To facilitate the quantitative estimation of the induced seismic hazard and risk, a ground motion prediction model has been developed for response spectral accelerations and duration due to these earthquakes that originate within the reservoir at 3 km depth. The model is consistent with the motions recorded from small-magnitude events and captures the epistemic uncertainty associated with extrapolation to larger magnitudes. In order to reflect the conditions in the field, the model first predicts accelerations at a rock horizon some 800 m below the surface and then convolves these motions with frequency-dependent nonlinear amplification factors assigned to zones across the study area. The variability of the ground motions is modeled in all of its constituent parts at the rock and surface levels.


Author(s):  
Molly Luginbuhl ◽  
John B. Rundle ◽  
Donald L. Turcotte

A standard approach to quantifying the seismic hazard is the relative intensity (RI) method. It is assumed that the rate of seismicity is constant in time and the rate of occurrence of small earthquakes is extrapolated to large earthquakes using Gutenberg–Richter scaling. We introduce nowcasting to extend RI forecasting to time-dependent seismicity, for example, during an aftershock sequence. Nowcasting uses ‘natural time’; in seismicity natural time is the event count of small earthquakes. The event count for small earthquakes is extrapolated to larger earthquakes using Gutenberg–Richter scaling. We first review the concepts of natural time and nowcasting and then illustrate seismic nowcasting with three examples. We first consider the aftershock sequence of the 2004 Parkfield earthquake on the San Andreas fault in California. Some earthquakes have higher rates of aftershock activity than other earthquakes of the same magnitude. Our approach allows the determination of the rate in real time during the aftershock sequence. We also consider two examples of induced earthquakes. Large injections of waste water from petroleum extraction have generated high rates of induced seismicity in Oklahoma. The extraction of natural gas from the Groningen gas field in The Netherlands has also generated very damaging earthquakes. In order to reduce the seismic activity, rates of injection and withdrawal have been reduced in these two cases. We show how nowcasting can be used to assess the success of these efforts. This article is part of the theme issue ‘Statistical physics of fracture and earthquakes’.


Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Tara I. Yacovitch ◽  
Bruno Neininger ◽  
Scott C. Herndon ◽  
Hugo Denier van der Gon ◽  
Sander Jonkers ◽  
...  

The Groningen natural gas field in the Netherlands – one of Europe’s major gas fields – deploys a “production cluster” infrastructure with extraction, some processing and storage in a single facility. This region is also the site of intensive agriculture and cattle operations. We present results from a multi-scale measurement campaign of methane emissions, including ground and airborne-based estimates. Results are compared with inventory at both the facility and regional level. Investigation of production cluster emissions in the Groningen gas field shows that production volume alone is not a good indicator of whether, and how much, a site is emitting methane. Sites that are nominally shut down may still be emitting, and vice-versa. As a result, the inventory emission factors applied to these sites (i.e. weighted by production) do a poor job of reproducing individual site emissions. Additional facility-level case studies are presented, including a plume at 150 ± 50 kg CH4 hr–1 with an unidentified off-shore emission source, a natural gas storage facility and landfills. Methane emissions in a study region covering 6000 km2 and including the majority of the Groningen field are dominated by biogenic sources (e.g. agriculture, wetlands, cattle). Total methane emissions (8 ± 2 Mg hr–1) are lower than inventory predictions (14 Mg hr–1) but the proportion of fossil fuel sources is higher than indicated by the inventory. Apportionment of methane emissions between thermogenic and biogenic source types used ethane/methane ratios in aircraft flasks and ground-based source characterization. We find that emissions from the oil and gas sector account for 20% of regional methane, with 95% confidence limits of (0%, 51%). The experimental uncertainties bound the inventory apportionment of 1.9%, though the central estimate of 20% exceeds this result by nearly 10 times. This study’s uncertainties demonstrate the need for additional research focusing on emissions apportionment, inventory refinement and offshore platforms.


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