The Jurassic Petroleum System in the Danish Central Graben

The Danish North Sea Fund and the Geological Survey of Denmark and Greenland, GEUS, have discussed the importance of a comprehensive study of the Jurassic Petroleum System in the Danish Central Graben. A proposal for a multi client project has been presented on a workshop held in Copenhagen in November 2010. A number of the companies holding licences for exploration for hydrocarbons in the Danish area have already shown their interest in supporting the proposed three year project through collaboration agreements with GEUS and it is decided that the study will be carried out by February 2011. The North Sea Fund fully supports the project and will participate in the workshops planned to be held twice a year. The outcome of the study will be of considerable value for companies active in the search for oil and gas in Denmark.

Even though the Danish Central Graben is a mature petroleum province, key aspects of the Jurassic Petroleum System are still poorly understood and furthermore, the Jurassic sedimentary system is stratigraphically and structurally complex. So far, a consistent regional seismic-stratigraphic framework has not been established, although such a framework is essential in unraveling the structural evolution and basin development. Recent work on the Jurassic sandstones indicates the need for a revision of the established stratigraphy. Prediction of reservoir quality is a major challenge in evaluating the Jurassic sandstones, so an examination of the diagenesis and its influence on the reservoir quality is of high value.

The present day knowledge on the distribution, quality and maturity of the Jurassic source rocks is limited, and a detailed understanding of the recorded variations in maturity and composition of Jurassic-sourced oils and delineation of potential kitchen areas has to be further investigated.

The study now starting up will expand on previous results published in the book: “The Jurassic of Denmark and Greenland” (Ineson and Surlyk, 2003). Relevant stratigraphic and seismic interpretations presented herein will be updated and revised. Correlation of logs will subsequently be integrated with interpretation of seismic data in order to set up a coherent seismic-stratigraphic framework. The database will include all released wells and 3D seismic surveys, thus updating the regional mapping of Jurassic units published by Britze et al. (1995).

The aim for the project is to establish a consistent seismic-sequence stratigraphic framework of the Jurassic in the Danish Central Graben, to provide a series of paleogeographical maps, showing the depositional environments, distribution of lithologies and potential sand source areas through time and to present an overview of reservoir sandstone characteristics, i.e. porosity, permeability, net sand, sediment petrography and diagenetic alterations.

Furthermore, it is an intension to outline the regional variation of source rocks/petroleum characteristics such as quality/type, maturity, likely kitchen areas and migration fairways and to present updated basin modelling studies in areas where proper source rocks and reservoirs can be anticipated.

A goal is to be able to present a synthesis of the Jurassic Petroleum System, covering prospectivity and hydrocarbon plays in the Jurassic of in the Danish Central Graben in a format applicable for all participating companies.

If you want further information, please contact the North Sea Fund; geologist Inger Salomonsen, isa@nordsoeen.dk