New findings with respect to key conditions controlling the Jurassic-Cretaceous petroleum system, Dutch Central Graben (W046)

The Netherlands represent a mature area for hydrocarbon exploration, and only less obvious
targets are left for finding more oil and gas. One of these targets is the Chalk Group. This
paper presents selected results of a multidisciplinary project that aims to develop a new
stratigraphic trap model and migration/charge model for the Chalk in the Netherlands. Here
we focus on the analysis of the Posidonia-Chalk system, with emphasis on both the Posidonia
source rock maturity history and the migration and charging conditions of the Chalk in the
Dutch Central Graben.
The Posidonia Shale Formation is the main oil-prone source rock in the Dutch Central
Graben. The only producing oil field in the Chalk in the Netherlands, is the Hanze Field
located in block F-2 between the Central Graben and the Step Graben. The strongly naturally
fractured reservoir is located in the Ekofisk and in the Maastrichtian part of the Ommelanden
Formation of the Chalk Group on top of a major salt diapir. The Chalk Group is absent by
erosion in the inverted central part of the graben and its thickness reaches not more than 300
m in most of the graben area. The Chalk is overlain by the sealing Lower Tertiary shales, and
is on top of the Lower Cretaceous shales/marls of the Rijnland Group. The Chalk overlies
Jurassic units in the inverted centre of the graben.
1D-3D basin modelling (Petromod v.10 of IES) was used to study the Posidonia-Chalk
system in the Dutch Central Graben (e.g. Verweij and Souto Carneiro Echternach 2008a),
while additional hydrodynamic analysis (e.g. Verweij 2008b) was used to improve our
understanding of the hydrocarbon charging and preservation conditions in the Chalk