Stress-based, statistical modeling of the induced seismicity at the Groningen gas field, The Netherlands

Abstract

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.

Seismicity at the Castor gas reservoir driven by pore pressure diffusion and asperities loading

“…Injection operations were stopped on September 17, 2013 29 . Nevertheless, as observed for other induced seismicity cases 4 , 5 , 33 , seismicity continued in the following days. Larger earthquakes occurred, peaking in three earthquakes with magnitude Mw >4 in early October 27 , before finally fading away.…”

Interevent-time distribution and aftershock frequency in non-stationary induced seismicity

“…Gas production in the Groningen field in the North of the Netherlands has resulted in induced seismicity with a rapidly increased non-stationary activity, amounting to a catalog of 397 events above the magnitude of completeness M = 1.3 in the period 1995-2018 ( Fig. 1a) [43][44][45][46][47][48][49][50][51] . The gas withdrawal causes reservoir compaction and associated stress build-up along pre-existing faults.…”

One year of cyclic unrest in a hydrothermal field as a harbinger of a volcanic eruption

“…Earthquake triggering is expected for positive changes of the induced CFS, while no triggering is expected for negative changes 40,41 . For simplicity, we assume that the number of earthquakes is proportional to positive CFS-changes and consider stress shadowing (Kaiser effect) by only allowing triggering if the absolute stress exceeds all precursory values 42,43 . Thus the predicted cumulative number of induced events becomes N(x, t) ~ max(CFS(x, time<=t)).…”