The US Geological Survey (USGS) has released an assessment estimating that 47 million bbl of oil and 876 Bcf of natural gas remain undiscovered in upper Paleozoic reservoirs within Wyoming’s Wind River, Bighorn, and Powder River basins, as well as parts of southern Montana, South Dakota, and Nebraska (Fig 1). Since the 1920s, these basins have produced 4 billion bbl of oil, but the remaining undiscovered resources are relatively limited.
USGS assessments focus on undiscovered, technically recoverable resources, using geology-based methodologies to evaluate potential reserves.
The oil and gas in these basins are trapped in structural and stratigraphic traps, with origins in organic-rich shales from formations such as the Minnelusa, Phosphoria, and Madison Group.
Advances in extraction technologies, including horizontal drilling and fracturing, have significantly influenced oil production and, consequently, how assessments are conducted.
“The shift to horizontal drilling with fracking has revolutionized oil production, and we’ve changed with it,” said Christopher Schenk, USGS geologist.
USGS oil and gas assessments began 50 years ago in response to an oil embargo, emphasizing the need to understand resource availability. These assessments continue to provide critical data for US energy policy and resource management. While these basins have historically been productive, the latest assessment suggests that the remaining undiscovered resources are limited compared to past production levels.