Abstract

Abstract Widely distributed deep-water fan sandstones of early Tertiary age form the reservoir for one of the most successful and prolific plays in the North Sea and NE Atlantic margin. Stratigraphic interpretation of a large well database provides the basis for mapping sand distribution and depositional environments in these two hydrocarbon provinces. Sand thickness maps for five Paleocene–Lower Eocene plays illustrate the intimate relationship between pre-existing structural features and sand distribution and facies in the North Sea. Large-scale depositional environment mapping gives an insight into the similarities and differences between basin evolution and sand distribution in North Sea and NE Atlantic margin basins. Both provinces were affected by the same succession of pre-break-up and syn-break-up tectonic and magmatic events that led to early Eocene continental separation and the formation of the NE Atlantic. The impact of these events was muted within the North Sea, which was protected from Paleocene rifting on the NE Atlantic margin by the Scotland–Shetland hinterland and from Paleocene–early Eocene volcanism by its more distant location. However, it was the combination of tectonic and thermal uplift of this clastic source area that contributed the large volumes of sand that accumulated in both these provinces.

Highlights

  • Lower Tertiary sandstone reservoirs deposited in deep-water submarine fan systems are widely distributed in the North Sea Basin, occurring in three broadly defined areas of sand accumulation: Moray Firth –Central Graben, South Viking Graben– Beryl Embayment and East Shetland Basin (Fig. 1)

  • The extension, uplift and volcanism that affected North Sea and NE Atlantic margin basin development during the Paleocene –early Eocene are related to two phases of tectonism and magmatism that preceded continental break-up and the start of seafloor spreading in the NE Atlantic during chron 24r at c. 54 Ma (Ahmadi et al 2003; Coward et al 2003; Lundin & Dore 2005; Passey & Hitchen 2011)

  • The main objective of the sand thickness and depositional environment mapping presented in this paper is to provide the regional context for more detailed evaluation of Lower Tertiary fan sandstones in the North Sea at the field and play fairway scale

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Summary

Data and methodology

In this paper a large interpreted well database, added to and revised over a period of more than thirty years, forms the basis for Lower Tertiary stratigraphic analysis and mapping in the North Sea, Faroe –Shetland, NE Rockall and Møre basins (Fig. 2). Their intimate association with reservoir sandstones, with the base of each sandstone package being marked by unconformity and the top by a highgamma mudstone Using this stratigraphic control, sand thickness maps have been produced for five Paleocene –Lower Eocene hydrocarbon plays in the North Sea: Maureen –Andrew, Balmoral/Heimdal, Forties, Dornoch/Sele and Beauly/Balder. Sand thickness maps have been produced for five Paleocene –Lower Eocene hydrocarbon plays in the North Sea: Maureen –Andrew, Balmoral/Heimdal, Forties, Dornoch/Sele and Beauly/Balder These regional surfaces occur in the Faroe – Shetland stratigraphic record, and can be identified in the NE Rockall and Møre basins (Waddams & Cordingley 1999; Mudge & Bujak 2001). Integration of a further 200 interpreted wells from these NE Atlantic margin basins with the North Sea stratigraphic database has provided the basis for regional mapping of Danian–Lower Ypresian depositional environments

North Sea and NE Atlantic margin stratigraphy
Forties sandstones
Dornoch and Sele sandstones
Beauly and Balder sandstones
Upper Danian depositional environments
Selandian depositional environments
Thanetian depositional environments
Discussion

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