The Lower Palaeozoic now fully cored and logged on Bornholm, Denmark

A 558 m long, complete section of the Lower Palaeozoic succession preserved onshore southern Bornholm has been compiled from five fully cored scientific wells, carried out between 2005 and 2012. The scientific programme included coring and geophysical logging of the five scientific wells that yielded a total of c. 750 m of partially overlapping cores as well as re-logging of water wells and acquisition of shallow seismic data. The last well drilled, the Sommerodde-1, cored the youngest preserved Silurian strata on Bornholm including strata not exposed in outcrops. The well penetrated 168.1 m of Silurian shales, 42.7 m of Upper Ordovician shales and 27.9 m of Alum Shale before it terminated at a depth of 250.3 m in the Lower Cambrian Norretorp Member of the Læså Formation. Th e Sommerodde-1 well documents that the Lower Silurian Cyrtograptus shale is at least 91.7 m thick and that the Rastrites shale is 76.4 m thick. The complete Lower Cambrian succession has previously been covered by the 316.0 m deep Borggård-1 well that terminated in basement rocks (Nielsen et al. 2006)

Shallow core drilling of the Upper Cretaceous Chalk at Stevns Klint, Denmark

The Upper Cretaceous – Danian succession in Denmark and most of NW Europe is composed mainly of chalk and associated shallower water carbonates deposited in a wide epeiric sea during an overall global sea-level highstand (e.g. Surlyk 1997). The Maastrichtian–Danian chalk has been intensely studied over the last 20 years, since it forms the most important reservoir rock for hydrocarbons in the North Sea Central Graben (e.g. Surlyk et al. 2003; Klinkby et al. 2005). In Denmark, thousands of water wells have been drilled through the succession as about 35% of the water consumption is from Maastrichtian chalk and Danian bryozoan limestone. During 2005 the new Cretaceous Research Centre (CRC) was established jointly at Geocenter Copenhagen by the Geological Institute, University of Copenhagen and the Geological Survey of Denmark and Greenland (GEUS) with financial support from the Danish Natural Science Research Council (FNU). CRC aims at studying the Earth System in a Greenhouse World, with special emphasis on the Upper Cretaceous – Danian chalk of NW Europe. The stable, long lasting marine macro-environment represented by the chalk sea provides a unique opportunity to analyse and link the depositional, geochemical and biological responses to external forcing at time scales ranging from the sub-Milankovitch to the million year range. The studies will be based on a wide range of methods, including seismic stratigraphy, palaeoecology, sequence-, cyclo- and biostratigraphy, isotope geochemistry, sedimentology and time series analysis. This paper presents the first preliminary results of a CRC drilling campaign at Stevns Klint, eastern Denmark (Fig. 1), where two shallow boreholes were drilled and logged from near the base of the Danian bryozoan limestone and down through the upper 350–450 m of the very thick Upper Cretaceous chalk section (Vejbæk et al. 2003). The cores represent the first complete sections through the Maastrichtian chalk of eastern Denmark

Shale gas investigations in Denmark:Lower Palaeozoic shales on Bornholm

The Cambrian to Lower Silurian succession in Denmark is mostly composed of organic-rich black shales that were deposited in an epicontinental sea during a period of high global sea level (Haq & Schutter 2008). The mid-Cambrian to early Ordovician Alum Shale was intensively studied in the 1980s for its source-rock properties (e.g. Buchardt et al. 1986). Recent attention has focused on its potential as an unconventional shale gas source (Energistyrelsen 2010). On southern Bornholm, many wells have been drilled through the Lower Palaeozoic succession because of its importance for groundwater exploitation. In western Denmark, only the deep exploration wells Slagelse-1 and Terne-1 have penetrated the Alum Shale, and knowledge of the unit west of Bornholm is thus very limited (Fig. 1)

Borggård-1 - ny stratigrafisk kerneboring på Bornholm

En 316 m dyb fuldt kernet boring på Sydbornholm udført maj-juli 2006 leverer for første gang præcise oplysninger om lithologien og tykkelsen af de nedre kambriske formationer i området. Boringen skulle desuden vise sig at rumme flere spændende overraskelser, bl.a. blev det konstateret, at de stærkt vandførende kvartsitter er næsten dobbelt så tykke som oprindeligt antaget

The Lower Palaeozoic now fully cored and logged on Bornholm, Denmark

A 558 m long, complete section of the Lower Palaeozoic succession preserved onshore southern Bornholm has been compiled from five fully cored scientific wells, carried out between 2005 and 2012. The scientific programme included coring and geophysical logging of the five scientific wells that yielded a total of c. 750 m of partially overlapping cores as well as re-logging of water wells and acquisition of shallow seismic data. The last well drilled, the Sommerodde-1, cored the youngest preserved Silurian strata on Bornholm including strata not exposed in outcrops. The well penetrated 168.1 m of Silurian shales, 42.7 m of Upper Ordovician shales and 27.9 m of Alum Shale before it terminated at a depth of 250.3 m in the Lower Cambrian Norretorp Member of the Læså Formation. Th e Sommerodde-1 well documents that the Lower Silurian Cyrtograptus shale is at least 91.7 m thick and that the Rastrites shale is 76.4 m thick. The complete Lower Cambrian succession has previously been covered by the 316.0 m deep Borggård-1 well that terminated in basement rocks (Nielsen et al. 2006)