Paleo-Five Project - Paleozoic petroleum potential of the five countries area, Southern-Central North Sea

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The Paleo-Five Project (2018-2020) is an international Joint Industry Project carried out by TNO-Geological Survey of the Netherlands in collaboration with the British Geological Survey (BGS). The present report is a data-rich compilation of all the analysis and results gathered, and establishes a new benchmark for the stratigraphy, structural history and source rock potential of the Lower Carboniferous for a large part of the economically important Central and Southern North Sea. The project addresses the cross-border geology of the Lower Carboniferous of the UK, Dutch, Danish, German and Norwegian sectors of the North Sea, with a primary emphasis on the stratigraphic and tectonostratigraphic framework of the Lower Carboniferous. The multidisciplinary research activities include legacy database compilation, outcrop analysis, palynological and palynofacies analysis, organic geochemical analysis, well correlation, and seismic interpretation.

A central foundation of the project is the study of a series of outcrops in Northumberland and the Scottish Borders area. These outcrop sections have been measured, interpreted in terms of lithology and depositional facies, and intensively sampled. 1600 m of stratigraphy were measured, spanning the Upper Devonian to middle Namurian interval, providing unique knowledge of the depositional environment and the diversity of potential source rock facies (coal, lacustrine, marine mudstones, carbonates). 332 samples were collected from these outcrops for palynological, palynofacies, and organic geochemical analysis. The subsurface component of this study initiated with the construction of a well database. A total of 181 wells penetrating the pre-Westphalian (i.e., Lower Carboniferous and/or older strata) were selected. For these wells, wireline log data, biostratigraphic and geochemical reports were collected. Using these data, chrono- and lithostratigraphic interpretations were made. These interpretations, together with the well-dated reference framework from the outcrops, lay the foundation for the stratigraphic synchronization of all these wells encountering the Lower Carboniferous. The structural and tectonostratigraphic analysis consisted of the interpretation of key regional seismic and well transects, combined with local mapping of key horizons such as the top Kyle Group. Four regional well panels, combining a total of 44 key wells, were constructed, illustrating the stratigraphy of the Devono-Carboniferous across the five national sectors and highlighting the stratigraphic synchronization proposed in this study. Three interpreted regional seismic panels were constructed, totaling more than 1600 km, and show the complex structural framework of the pre-Permian in the study area. These panels cross several faults that are interpreted as syndepositional faults during the Carboniferous (such as the newly defined P5 Fault located in the UK and Dutch sector) as well as several basement structural highs. A new base-Permian subcrop map was constructed based on the new stratigraphic and structural results and represent the first ever combined BPU subcrop map in the five country North Sea area. A new crustal model is also proposed based on previous published models and adapted using results from this study.