Maturity and source-rock potential of Palaeozoic sediments in the NW European Northern Permian Basin

The Northern Permian Basin is located in the offshore area SSW of Norway, NNW of Denmark and east of Scotland. This basin is filled mainly by Lower Permian aeolian desert sediments and volcanics, plus Upper Permian evaporitic sediments. The aeolian sandstone is an excellent reservoir rock and is generally capped by thick layers of salt that potentially form a tight cap rock. The highest risk in the petroleum exploration of the Palaeozoic Northern Permian Basin is linked to the presence of source rocks. Palaeozoic source-rock candidates in the Northern Permian Basin area may be present among Lower Palaeozoic marine sediments, within Devonian–Carboniferous lacustrine/deltaic pre- and syn-rift sediments and as Permian marine shales. This study investigates Lower Palaeozoic marine shales, lacustrine Devonian mudstones, Carboniferous mudstones and coals and marine Permian shales in order to assess the thermal maturity, source-rock potential and distribution of Palaeozoic sediments in the Northern Permian Basin region. The majority of the investigated samples were within the oil window in terms of thermal maturity. Lower Palaeozoic marine sediments may have generated both oil and gas, while Upper Palaeozoic coals and mudstones are dominantly gas-prone source rocks. Middle Permian marine shales (Kupferschiefer) are a good oil-prone source rock. Generation and expulsion of hydrocarbons from Lower Palaeozoic source rocks in the eastern parts of the Northern Permian Basin probably began in the Upper Silurian, with peak oil generation in Carboniferous times. Upper Palaeozoic rocks in the same area matured rapidly in Early Triassic times. The likely presence of multiple Palaeozoic source rocks suggests that hydrocarbons were generated in the Northern Permian Basin.