Time–Space Evolution of the Groningen Gas Field in Terms ofb-Value: Insights and Implications for Seismic Hazard

Abstract

The Groningen gas field, located in the northeast of The Netherlands, is the Europe’s largest onshore gas field. It was discovered in 1959 and production started in 1963: Continuous production leads to reservoir compaction and subsidence, gradually loading preexisting fault and induced seismicity that started about 30 yr into the production. The seismic hazard and risk related to the induced seismicity is determined not only for the rate of activity, but it is also equally influenced by the relative size distribution of the seismicity—the b-value. I reanalyze the spatial and temporal evolution of the b-value in the field using an alternative approach to overcome magnitude in completeness heterogeneity, and link it to the evolution of fault loading and subsidence. Spatial variations of b-values are found to vary between 0.61 and 1.3, with the lowest observed values observed in the location of the 2012 M 3.6 Huizinge earthquake. In the last 10 yr, the mapped b-values are more homogeneous throughout the field. The spatial and temporal evolution of the b-value in the field in this study is shown to be quite complex, and systematically linked it to the evolution of fault loading, absolute compaction, and the rate of compaction—an important finding that offers new insights into hazard reduction and mitigation strategies of extraction relation-induced seismicity. Compaction rates below 2 mm/yr are not correlated to seismicity above M 2.0 in the history of the field, suggesting that low-volume production may be safer than that previously assumed.