Undiscovered Oil and Gas in the Central European Basin's Mesozoic Rocks

As part of its National and Global Petroleum Assessment, the U.S. Geological Survey (USGS) used a geology-based method to estimate the undiscovered, technically recoverable conventional oil and gas in the Mesozoic total petroleum systems of the Central European Basin System, which stretches from Ireland east to Germany and from Germany north to Norway and the Faroe Islands. The mean estimates are 5.8 billion barrels of oil and 22.4 trillion cubic feet of gas.

Fifty years of intensive exploration in these Mesozoic systems have found more than 60 billion barrels of conventional oil and 80 trillion cubic feet of conventional gas. Apart from the Faeroes-Shetland-Orkney Basin, the regional graben systems are at a mature stage of exploration. The study asks how much remains to be found.

Figure 1. The eight conventional assessment units in the two Mesozoic total petroleum systems. Base map from the U.S. Department of the Interior, National Park Service. Credit: U.S. Geological Survey.

Two petroleum systems

Upper Jurassic–Lower Cretaceous. The main source rock is the Kimmeridge Clay Formation, with its equivalents the Mandal and Draupne Formations. As much as 1,000 meters of organic-rich shale accumulated in regional rift systems — the Viking Graben, East Shetland Basin, Moray Firth Basin–Witch Ground Graben, Central–Tail End Graben and Faeroes-Shetland-Orkney Basin — in the Late Jurassic and Early Cretaceous. After regional thermal relaxation and the end of extension in the Early Cretaceous, as much as 2,000 meters of Late Cretaceous chalk and Paleogene shale and deepwater sandstone was deposited on top, providing the overburden that brought the Kimmeridge source rocks to thermal maturity. That oil and gas moved upward into salt-influenced structural traps and stratigraphic traps in the grabens, and sideways into the neighbouring East Shetland Platform and Utsira High–Horda Platform. The main reservoirs are Jurassic sandstones, Upper Cretaceous chalks and Paleogene sandstones.

Mesozoic Composite. Defined in the Lower Saxony Basin and the West Netherlands Basin, this system's main source rocks are the Lower Jurassic Posidonia Shale and the Lower Cretaceous Wealden Shale.

Results

Fully risked mean estimates by assessment unit:

The totals are 5,848 million barrels of oil (F95–F5 range 2,836 to 10,279), 22,356 billion cubic feet of gas (11,472 to 37,428) and 633 million barrels of natural gas liquids (314 to 1,085); F95 means a 95 percent chance of at least that amount. About 50 percent of the undiscovered resources are estimated to lie in the less-explored Faeroes-Shetland-Orkney Basin.

Sources

Based on "Assessment of Undiscovered Conventional Oil and Gas Resources in Mesozoic Total Petroleum Systems of the Central European Basin System, 2019," U.S. Geological Survey Fact Sheet 2022–3069 (October 2022), published by the U.S. Geological Survey; rewritten in hubnx's own words.

• The map and the results by assessment unit come from the fact sheet's PDF: https://pubs.usgs.gov/fs/2022/3069/fs20223069.pdf
• The fact sheet's summary line calls these "continuous" resources; everywhere else, including its title and results table, it assesses conventional resources, which this page follows.
• The fact sheet's cross-section of the Central Graben, modified from Cornford (1994), is not reproduced. Input data are in Schenk (2022), a USGS data release.