Undiscovered Oil and Gas in the Barents Sea: The USGS 2021 Assessment

The U.S. Geological Survey estimates how much oil and gas remains to be found around the world. Its 2021 assessment of the Barents Sea area, which the report lists under Norway and Russia, estimated the undiscovered conventional oil, gas and natural gas liquids that could be recovered with existing technology.

The five assessment units of the Barents Sea area. U.S. Geological Survey.

A basin built in many stages

The Barents Sea area's geology reflects repeated deformation of an uneven basement:

• Devonian: stretching of the crust reopened old faults, forming a series of horsts and grabens that filled with up to 6 kilometers of sediment.
• Carboniferous and Permian: thermal subsidence let several thousand meters of land and marine sediment accumulate, including widespread coal beds and organic-rich marine shales — both possible sources of petroleum. As the Uralian Ocean closed in the Permian, a thrust belt and basins formed in the east and filled with thousands more meters of sediment. Permian salt structures exist in the west and may exist in the east.
• Middle Triassic to Early Jurassic: collision of the Kara terrane raised the Novaya Zemlya fold belt and created a foredeep in the east that became an ultradeep basin with up to 20 kilometers of sediment. The west was mostly a shallow platform, and a forebulge west of the foredeep caused up to 1.5 kilometers of erosion there. Folding produced broad anticlines, which later became important traps for oil and gas.
• Cretaceous: thermal subsidence made room for layers of sandstone, laid down in environments from rivers to the deep sea, that can serve as reservoirs.
• Late Cretaceous onward: in the west, up to 3 kilometers of uplift and erosion through the Oligocene, and stretching during the Neogene opening of the Norwegian Sea, may have caused oil and gas to leak away or move.

All five assessment units lie entirely north of the Arctic Circle. The report divides the area into an eastern part (the North Barents and South Barents basins) and a western part (the Barents platform).

Where the oil and gas come from

USGS defined a single Paleozoic–Mesozoic Composite Total Petroleum System containing five assessment units. Its sources are gas from Carboniferous and possibly Permian coal beds and marine shales, and oil and gas from organic-rich Triassic, Jurassic and Cretaceous marine shales.

• East: deep burial has pushed all source rocks past the temperatures that generate oil and into those that generate gas. Triassic marine shales, hundreds of meters thick and with total organic carbon of up to 12 weight percent, are the most viable source rocks, and coal beds are thought to be a major source of gas.
• West: source rocks are within both the oil and the gas windows, and Jurassic organic-rich shales are thought to be the most viable source.

In the three eastern units, oil and gas generated during deep burial from the Permian to the Cretaceous is thought to have migrated into sandstone reservoirs in folds, faulted anticlines and stratigraphic traps from shelf to slope, and into basin-floor fans. Salt movement may also have created traps, and many large structures have not yet been drilled. In the two western units, oil and gas from Carboniferous coal and Permian, Triassic and Jurassic shales is thought to have moved into similar traps, but repeated uplift may have eroded reservoirs and let oil and gas escape.

The estimates

The fully risked mean estimates for the whole area are:

F95 means there is a 95 percent chance of at least that amount; F5, a 5 percent chance. Most of the undiscovered oil (93 percent) and gas (98 percent) is estimated to lie in the eastern part of the area.

Mean estimates by assessment unit:

The Barents Platform North unit was assigned an assessment-unit probability of 0.8; the other four, 1.0.

Sources

• Christopher J. Schenk, Tracey J. Mercier, Cheryl A. Woodall, Geoffrey S. Ellis, Thomas M. Finn, Phuong A. Le, Kristen R. Marra, Heidi M. Leathers-Miller and Ronald M. Drake II, "Assessment of undiscovered conventional oil and gas resources of the Barents Sea area, 2021," U.S. Geological Survey Fact Sheet 2023–3019: https://doi.org/10.3133/fs20233019