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December 2021

Paleo-Five: the final frontier in North Sea exploration

As part of the cross-border Paleo-Five Project, researchers from the Geological Survey of the Netherlands (GDN) and the British Geological Survey (BGS) worked on mapping out ancient, deeply buried rock strata from the Carboniferous period. Experts from the fields of geology, geochemistry, paleo-ecology, and seismology studied the geological distribution and composition of these rock layers for an offshore area shared by five countries in the southern and central North Sea.

300-million-year-old rock strata

The Carboniferous is a geological period that lasted from approximately 350 to 300 million years ago. The oldest piece of the Netherlands originated during this period; the Heijmans Quarry in South Limburg has surface-level rock layers from the Carboniferous. In the rest of the Netherlands’ (on- and offshore) subsurface, these rock layers are often buried so deep that knowledge from drilled oil and gas wells is insufficient. However, as a significant source of natural gas, these rock layers are important. 

Regional collaboration

For a long time, oil and gas were extracted from rock layers from the Triassic, Jurassic and/or Cretaceous. But there has been renewed interest in the deeper, older, and less accessible parts of the subsurface as potential gas reservoirs, including from the Carboniferous. Nevertheless, geological strata do not stop at national borders, making international cooperation a necessity when trying to understand their history. This is why the Geological Survey of the Netherlands (GDN) and the British Geological Survey (BGS) joined forces for a large-scale, cross-border study of the hydrocarbon potential of Paleozoic units in an area shared by five countries (the Netherlands, the United Kingdom, Germany, Denmark, and Norway) in the south-central North Sea: the ‘Paleo-Five’ Project.

Synchronised stratigraphic scheme

Geological maps resulting from regional exploration studies generally end at national borders. Moreover, countries often use their own, specific names for different rock layers, a fact that often leads to mismatching and confusion in cross-border studies. The first tangible achievement of the Paleo-Five study has been a synchronised stratigraphic scheme of the structure and names of the ancient Carboniferous rock strata in the five North Sea countries.

Pre-Westphalian source rocks

An important but poorly understood aspect of the Paleozoic petroleum system are the pre-Carboniferous source rocks, the pre-Westphalian. Thanks to the Paleo-Five Project, we now better understand that these pre-Carboniferous earth layers were deposited in a shallow, tideland delta in an area covering the five countries.

Through the Paleo-Five Project, we are now integrating cross-border log correlations and collaborating on sedimentological fieldwork. New analyses in the fields of palynology and organic geochemistry (such as pyrolysis) have been used to better understand the composition of the Carboniferous layers and date them more precisely. On top of this, the project was supported by a regional, integrated interpretation of seismic and gravity/maturity data.

Milestone project

Sponsored by sixteen exploration and production companies with a shared keen interest in the Paleozoic of the south-central North Sea, the results of the Paleo-Five Project are a milestone for current and future exploration efforts focused on the Paleozoic of the North Sea. The report containing all the findings will be partially released by the end of 2022.

Interested in more information? Please contact Friso Veenstra via the blue ‘mail directly’ button below.

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