Groningen is the largest onshore gas field under production in Europe. The pressure depletion of the gas field started in 1963. In 1991, the first induced micro-earthquakes have been located at reservoir level with increasing rates in the following decades. Most of these events are of magnitude less than 2.0 and cannot be felt. However, maximum observed magnitudes continuously increased over the years until the largest, significant event with $$M_L=3.6$$ML=3.6 was recorded in 2014, which finally led to the decision to reduce the production. This causal sequence displays the crucial role of understanding and modeling the relation between production and induced seismicity for economic planing and hazard assessment. Here we test whether the induced seismicity related to gas exploration can be modeled by the statistical response of fault networks with rate-and-state-dependent frictional behavior. We use the long and complete local seismic catalog and additionally detailed information on production-induced changes at the reservoir level to test different seismicity models. Both the changes of the fluid pressure and of the reservoir compaction are tested as input to approximate the Coulomb stress changes. We find that the rate-and-state model with a constant tectonic background seismicity rate can reproduce the observed long delay of the seismicity onset. In contrast, so-called Coulomb failure models with instantaneous earthquake nucleation need to assume that all faults are initially far from a critical state of stress to explain the delay. Our rate-and-state model based on the fluid pore pressure fits the spatiotemporal pattern of the seismicity best, where the fit further improves by taking the fault density and orientation into account. Despite its simplicity with only three free parameters, the rate-and-state model can reproduce the main statistical features of the observed activity.
The occurrence of felt earthquakes due to gas production in Groningen has initiated numerous studies and model attempts to understand and quantify induced seismicity in this region. The whole bandwidth of available models spans the range from fully deterministic models to purely empirical and stochastic models. In this article, we summarise the most important model approaches, describing their main achievements and limitations. In addition, we discuss remaining open questions and potential future directions of development.
" wird seit Anfang der 80 er Jahre in der Personalforschung und in der Managementpraxis diskutiert. In diesem Artikel wird ein Modell zur "Inneren Kündigung" erarbeitet, dass es möglich macht, (1) das Phänomen von ähnlichen Konzepten wie dem Burnout abzugrenzen und (2) im Rahmen empirischer Forschung zu operationalisieren. Das theoretische Modell wurde vom Autor in einer schriftlichen Personalbefragung in einer öffentlichen Verwaltung getestet. In dem Beitrag werden Teilergebnisse aus dem Forschungsprojekt referiert: Sie betreffen die quantitative Verbreitung, die Erscheinungsformen und Ursachen des Phänomens. Zentrale Ergebnisse sind, dass (1) eine verfehlte betriebliche Karrierepolitik eine herausragende Rolle als "Verursacher" für das Problem spielt und dass (2) die betroffene Gruppe von Mitarbeitern sich heterogener darstellt, als in der Literatur angenommen wird.
Summary
Natural gas can be temporarily stored in a variety of underground facilities, such as depleted gas and oil fields, natural aquifers, and caverns in salt rocks. Being extensively monitored during operations, these systems provide a favorable opportunity to investigate how pressure varies in time and space and possibly induces/triggers earthquakes on nearby faults. Elaborate and detailed numerical modeling techniques are often applied to study gas reservoirs. Here we show the possibilities and discuss the limitations of a flexible and easily formulated tool that can be straightforwardly applied to simulate temporal pore-pressure variations and study the relation with recorded microseismic events. We use the software POEL (POroELastic diffusion and deformation) which computes the poroelastic response to fluid injection/extraction in a horizontally layered poroelastic structure. We further develop its application to address the presence of vertical impermeable faults bounding the reservoir and of multiple injection/extraction sources. Exploiting available information on the reservoir geometry and physical parameters, and records of injection/extraction rates for a gas reservoir in southern Europe, we perform an extensive parametric study considering different model configurations. Comparing modeled spatiotemporal pore-pressure variations with in situ measurements, we show that the inclusion of vertical impermeable faults provides an improvement in reproducing the observations and results in pore-pressure accumulation near the faults and in a variation of the temporal pore-pressure diffusion pattern. To study the relation between gas storage activity and recorded local microseismicity, we applied different seismicity models based on the estimated pore-pressure distribution. This analysis helps to understand the spatial distribution of seismicity and its temporal modulation. The results show that the observed microseismicity could be partly linked to the storage activity, but the contribution of tectonic background seismicity cannot be excluded.
<span class="fett">Ziel:</span> Darstellung der Vermittlungsquoten in die stationäre Alkoholentwöhnungsbehandlung (AEB) nach qualifiziertem Entzug (QE) auf einer Spezialstation eines Allgemeinkrankenhauses. Die Ergebnisse werden mit anderen in der deutschsprachigen Literatur veröffentlichten Vermittlungsquoten verglichen. </p><p> <span class="fett">Methodik:</span> Die Untersuchung umfasst alle Alkoholabhängigen (n=194), die sich im Untersuchungszeitraum (Mai bis Dezember 2004) einer stationären Behandlung unterzogen. Davon nahmen n=89 am QE teil (46 %). Die Datenerhebung erfolgte auf Basis der psychiatrischen Basisdokumentation (BADO), ergänzt um ein suchtmedizinisches Modul sowie Erhebungen der Sozialarbeiter über die tatsächliche Inanspruchnahme. </p><p> <span class="fett">Ergebnisse:</span> 29 % aller QE-Patienten entschieden sich für eine AEB. Die Gruppe der QE-Patienten wurde in zwei Untergruppen separiert:Patienten mit und ohne AEB-Indikation. Von den QE-Patienten, bei denen eine AEB-Indikation gestellt wurde,traten 44 % eine AEB an. </p><p> <span class="fett">Schlussfolgerungen:</span> Die Vermittlungsquoten sind aus suchtmedizinischen Erwägungen nach Untergruppen zu differenzieren. Nicht bei allen QE-Patienten ist eine anschließende AEB indiziert.
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