ABSTRACT The Permian Rotliegend sandstone reservoir in the Groningen Field forms the largest onshore gas accumulation in Europe (2,900×10 9 m 3 or 100 Tcf Gas Initially In Place). The gas is contained in a high-quality dryland sandstone reservoir at approximately 2,900 m below sea level. The Groningen Field was discovered in 1959 by well Slochteren-1 with production starting in 1963. In this paper, the different phases of field development are discussed, illustrating the improved understanding of the subsurface over the past five decades through continued data acquisition like coring and advancements in technology, particularly of 3D seismic. The initial field development phase took some fifteen years, during which 29 well cluster locations were built and a total of over 300 wells were drilled for production and observation purposes. Integration of acquired data from the field together with state-of-the-art static and dynamic modelling technology now allow operating the Groningen system as a smart field, which requires only a few operators to produce up to 255×10 6 m 3 /d (9×10 9 scf/d) of gas on peak days during winter. Interestingly, the main focus of early exploration drilling was on oil prospects in Zechstein carbonates, and only with well Slochteren-1 did the focus change to gas prospects in the underlying Rotliegend Group. As is well established now, this gas petroleum system of Palaeozoic origin is the most important one in the Netherlands and is responsible for the generation of the Groningen Field gas predominantly during the Jurassic and, less importantly, during the Tertiary. Furthermore, a characterisation of the Rotliegend reservoir is provided. Its complex reservoir architecture is, firstly, a function of the sedimentary facies distribution, ranging from proximal alluvial-fan deposits in the south to playa-lake deposits in the north and, secondly, of the multiphase structural deformation of the Groningen High in the northern Netherlands. Diagenetic impairment of reservoir quality plays only a minor role in the field, which is related to the relatively early gas charge in the field. Gas retention over such a long time is attributed to the perfect top seal formed by the Zechstein evaporites. Fifty years after discovery, the Groningen Gas Field is still the most important gas supplier in Europe, with the end of field life expected in some fifty years from now. A review of this history to date is presented in this paper.

ABSTRACT Due to the nature of the depositional environment and most importantly the lack of (bio) stratigraphic control, it remains difficult to establish a robust and reliable stratigraphic framework for the Upper Rotliegend which can be used as a guideline to better understand the internal architecture. The most important challenges encountered are the identification of the large-scale basin architecture and basin fill, the identification of a sequence stratigraphic model for (semi-) arid continental deposits, and the relationship between the distribution of Upper Rotliegend sediments and the underlying Variscan structural framework. Based on the present-day knowledge and status of particular stratigraphic aspects, it can be concluded that a single “silver bullet” solution does not exist for providing a more profound understanding of the depositional model. It is evident that none of the methods available should be used in isolation but rather integrated in the framework of sequence stratigraphy providing the petroleum geologist a genetic and predictive geological model.