Upper Permian as a new play model on the mid-Norwegian continental shelf: Investigated by shallow stratigraphic drilling

摘要

A 750 m-thick, fully marine succession of sandstones, coarsegrained turbidites, shales, and reworked sabkha sediments has been cored on the eastern margin of the mid-Norwegian shelf. The succession has been dated as Upper Permian-Lower Triassic and is comparable to rocks of the same age exposed onshore East Greenland. These data demonstrate that the marine depositional basin between Greenland and Norway extended much farther east than previously thought. Reddish, shallow-marine sandstones in the lower 170 m of the cored succession probalby represent reworking of older sedimentary rocks present ot the east of the drill sites. This suggests that Upper Devonian-Lower Permian sediments were deposited on Caledonian basement east of the present-day limits of the basin. The cored succession also contains source rocks that can be stratigraphically correlated with the oil-prone source rocks of the Upper Permian Ravnefjeld Formatoin onshore East Greenland. Some of the cored sandstone intervals were stained with light, nonbiodegraded oil that most likely was sourced from Upper Permian or, alternatively, Lower Triassic mudstones. Reworked fragments of reef-building organisms in Upper Permian turbidites and Upper Permian carbonates encountered in an explorartion well on the Nordland Ridge indicate that carbonate deposition and reef building occurred on structural highs on the Trondelag Platform. The observations from the cored successions are key elements in a new Paleozoic play model on the mid-Norwegian continental shelf and include the first evidence for the existence of an Upper Permian source rock in the area, with Upper Permian carbonates or sandstones or Triassic-Jurassic sandstones as reservoir.