New stratigraphic insights in the ’Late Jurassic’ of the Southern Central North Sea Graben and Terschelling Basin (Dutch Offshore) and related exploration potential

Abstract

IMiddle Jurassic -Early Cretaceous strata are a target for oil and gas exploration in the Dutch offshore. During the initial stages of the 'Late Jurassic' offshore exploration, various oil fields and a few gas fields were discovered of which only one, the F3-FB field, proved to be economically viable.In the Northern Offshore of the Netherlands, latest Middle Jurassic (Callovian) -earliest Cretaceous (Ryazanian) strata are mostly limited to the Dutch Central Graben and Terschelling basins. Outside the Dutch Central Graben and the Terschelling Basin only thin veneers of these strata occur on the fringing highs such as the Schill Grund High and the Step Graben. The geology of this non-marine to shallow marine succession is complex. The combination of lateral facies changes, repetitive log and facies characteristics in time, sea-level and climate changes, salt tectonics and structural compartmentalisation hamper straightforward seismic interpretation and log correlation. The large number of lithostratigraphic units defined in the Stratigraphic Nomenclature of the Netherlands illustrates the complexity of this time-interval.In recent years, new biostratigraphic techniques and newly acquired stratigraphic data led to the identification of a series of events which can be related to the tectonic, climatic, environmental and stratigraphic development of the 'Late Jurassic' in the Dutch Central Graben and Terschelling basins. Based on these data, three stratigraphic sequences can be recognized. Sequence 1 (Callovian -earliest Kimmeridgian) records the initiation of the Dutch Central Graben, Sequence 2 (early Kimmeridgian -early Portlandian) that of the initiation of the Terschelling Basin. During sequence 3 (late Portlandian -Ryazanian) the Dutch offshore was draped by a regional transgression. These insights have directly impact on the exploration potential, which is discussed in two play concepts. The first is a strat-trap play in the fluvial/paralic sediments of Sequence 1 in the lows between the graben boundary and salt domes. The second example is the Spiculite play, which comprises a bioclastic sandstone reservoir at the top of a dome with a 4-way dip closure. These two examples highlight the necessity of understanding the paleoenvironment and geography for assessing the future exploration potential.

Tectonostratigraphy of a rift basin affected by salt tectonics: synrift Middle Jurassic–Lower Cretaceous Dutch Central Graben, Terschelling Basin and neighbouring platforms, Dutch offshore

“…Based on the integrated results of the tectonostratigraphic analysis, core description and palynological analyses carried out in the Dutch offshore, as well as regional stratigraphic analysis of Verreussel et al (2018), this study acknowledges and strengthens the recently developed tectonostratigraphic threefold subdivision for the Middle Jurassic-Lower Cretaceous interval in the Dutch offshore (Abbink et al 2006). The new chronostratigraphic framework proposed in the present paper (Fig.…”

“…A new series of palynological analyses was conducted, utilizing core and cuttings material from 24 wells, combined with legacy data from more than 100 exploration wells in the Danish and Dutch offshore (Abbink et al 2006;Munsterman et al 2012;Verreussel et al 2018). This enabled the definition of a regional dinocyst zonation that includes 4 zones and 18 subzones for the Middle CallovianBarremian (Verreussel et al 2018, fig.…”

“…Abbink et al (2006), Munsterman et al (2012) and Verreussel et al (2018; figs 2-4) divide this interval into three major tectonostratigraphic phases (referred to here as tectonostratigraphic mega-sequences or TMS; Fig. 1).…”

Revision and update of the Callovian-Ryazanian Stratigraphic Nomenclature in the northern Dutch offshore, i.e. Central Graben Subgroup and Scruff Group

“…These events resulted in the classification of three major strati graphic sequences in the Late Jurassic and one in the overlying earliest Cretaceous interval, which are related to tectonic, climatic, environmental and stratigraphic development (Abbink et al, 2006;Fig. 2).…”

“…Several studies contributed to this progress, e.g. : Abbink et al (2006), Herngreen et al (2000Herngreen et al ( , 2003, Duin et al (2006), Wong (2007), Andsbjerg & Dybkjaer (2003), Michelsen et al (2003), Johannessen (2003), Fraser et al (2003), Coward et al (2003) and Lott et al (2010). New palynological techniques (e.g.…”