Shale Oil and Gas in Germany's Lower Saxony Basin: A USGS Assessment, 2020

As part of its National and Global Petroleum Assessment, the U.S. Geological Survey (USGS) used a geology-based method to estimate how much undiscovered, technically recoverable oil and gas lies in shales of the Lower Saxony Basin in Germany. The mean estimates are 321 million barrels of shale oil and 435 billion cubic feet of shale gas.

The basin

The Lower Saxony Basin lies in the southern part of what the USGS defines as the Northwest German Basin Province. In the Mesozoic it evolved from an extensional regime into a large, complexly structured half graben trending east–west, between the Pompeckj terrane to the north and the Rhenish Massif and Lower Saxony Mountains to the south.

Two organic-rich shales are the source rocks:

• the Posidonia Shale, of Early Jurassic age, laid down across central Europe and present throughout the basin — a marine source rock with up to 20 weight percent total organic carbon, hydrogen index values up to 700 milligrams of hydrocarbon per gram of organic carbon, and an average thickness of 25 meters, reaching up to 100 meters in the Gifhorn Trough;
• the Wealden Shale, of Early Cretaceous age, in the western half of the basin — generally interpreted as a lacustrine source rock, with up to 14 weight percent total organic carbon, hydrogen index values up to 750, and an average thickness of 25 meters.

A deformed, deeply buried history

In the south of the basin, several kilometers of Jurassic and Cretaceous sediment buried these shales and heated them deep into the gas window, with vitrinite reflectance values of 5 percent or more. Along the more shallowly buried northern margin and in the Gifhorn Trough, they are immature or only marginally mature.

Compressional deformation during the Late Cretaceous Alpine orogeny inverted most of the earlier extensional structures. As much as seven kilometers of sediment was then uplifted and eroded in the south, and oil and gas in reservoirs there, or held in the shales, may have been lost. In the north and in the Gifhorn Trough, the shales reached thermal maturity for oil generation mainly through burial in the Cenozoic, and the oil they generated migrated into Late Cretaceous structures created during the Alpine orogeny along the northern margin or into salt-related structures in the Gifhorn Trough. These fractured, organic-rich shales may expel oil efficiently, which could leave still less oil behind in them.

Compared with many productive U.S. shale oil and gas plays, the Posidonia and Wealden Shales here are more deformed and broken up, which may reduce both how much oil and gas they hold and the area over which they hold it.

What was assessed

The USGS defined two total petroleum systems with five continuous assessment units (AUs).

Figure 1. The three assessment units of the Posidonia Shale total petroleum system. Base map from the U.S. Department of the Interior, National Park Service. Credit: U.S. Geological Survey.

Figure 2. The two assessment units of the Wealden Shale total petroleum system. Credit: U.S. Geological Survey.

Results

Mean estimates of undiscovered, technically recoverable resources, fully risked:

The ranges from F95 (a 95 percent chance of at least that much) to F5 are 75 to 696 million barrels of oil, 84 to 948 billion cubic feet of gas, and 0 to 5 million barrels of natural gas liquids. Of the 435 billion cubic feet of gas, 353 — about 81 percent — is associated gas, leaving 82 billion cubic feet of nonassociated shale gas.

Sources

Based on "Assessment of Continuous Oil and Gas Resources in the Lower Saxony Basin of Germany, 2020," by the USGS Lower Saxony Basin Assessment Team (Christopher J. Schenk and others), U.S. Geological Survey Fact Sheet 2022–3081 (January 2023), published by the U.S. Geological Survey; rewritten in hubnx's own words.

• The maps and the results by assessment unit come from the fact sheet's PDF: https://pubs.usgs.gov/fs/2022/3081/fs20223081.pdf
• Input data are in Schenk (2022), a USGS data release; the fact sheet also cites Betz and others (1987), Adriasola Muñoz and others (2007), Bruns and others (2013), Kockel and others (1994), Stock and Littke (2018), Petmecky and others (1999), Schwarzkopf and Leythaeuser (1988), Schwarzkopf (1990), Leythaeuser and others (1988), Song and others (2017), Fang and others (2019) and Rippen and others (2013).