How much oil and gas remains in the geologic reservoirs that produced much of Wyoming’s historic oil production?
The U.S. Geological Survey recently took its best shot at answering that question, finding “there are technically recoverable resources of 47 million barrels of oil and 876 billion cubic feet of gas,” according to a March 13 report from the USGS.
Christopher Schenk, the USGS geologist who prepared the report, told Cowboy State Daily how his team arrived at its findings.
“We spent some time looking at all the available data,” said Schenk. “And in the case of these basins in Wyoming there's been exploration going on for over 100 years. So, there's quite a bit of information.”
Schenk explained that in this assessment, the USGS looked at the Paleozoic sandstones in Wyoming and parts of southern Montana as well as western South Dakota and Nebraska.
“We've repeatedly assessed these over the years, and with the amount that's been discovered in these units over the last 100 years,” said Schenk, referring to the total amount of oil pulled from the Powder River, Wind River and Bighorn basins. “It's approximately 4 billion barrels in these three basins. And what we're saying is there's been so much exploration, so much discovery, it's down to, approximately 47 million (barrels).
“And that's the potential that's out there. It's the tail end of it, but you know, 47 million barrels of oil is still substantial. It's not like it's a bonanza. But it's not a small amount of oil.”
Enhanced Oil Recovery methods, such as using pressurized CO2 to extract additional oil from known reserves, could ultimately increase the number of barrels.
That’s why Schenk said his team measured “recoverability using today's technology, whatever that may be. And that includes enhanced oil recovery. We get a look at our databases, and we see that influence in there. We can actually see the influence of the EOR so we include all that.”
Wyoming Response
Ranie Lynds, who manages the Wyoming State Geological Survey (WSGS) Energy and Minerals Team, explained the recent USGS assessment is only part of the story when it comes to the state’s oil and gas deposits underground.
“There's many different types of reservoirs in Wyoming,” Lynds told Cowboy State Daily. “This assessment is only looking at the Paleozoic age reservoirs. So these would be the deeper, older rocks in the state. And it's only looking at how much oil has not yet been discovered in these reservoirs. It is trying to assess what's left and what nobody really knew about before this study.
“I think it's worth mentioning that Paleozoic reservoirs throughout Wyoming account for much of the state's historic oil production. But today, exploration and drilling targets are continuous reservoirs of Cretaceous age, and they're not assessed as part of the study.”
Jeremy Ring, a geologist who works with Lynds at the WSGS, said these types of assessments have been done before by the USGS.
“They put out one on the Lewis Shale assessment in the greater Green River Basin that came out in 2023, where they did the same kind of assessment and came up with a number for that specific reservoir,” said Ring. “Doing it based on the specific reservoirs allows the general public to understand in this one focused area what the oil volumes look like.”
The Petroleum Association of Wyoming keeps an eye on oil volumes underground. In its response to the USGS report, PAW emphasized “ongoing technological advancements” for reaching oil deposits in Wyoming.
“This assessment only captures a fraction of the state’s energy potential,” Ryan McConnaughey told Cowboy State Daily in an email after reviewing the USGS findings.
McConnaughey is the vice president and director of communications for PAW, and he said horizontal drilling and hydraulic fracturing will remain “pivotal” in exploration as “the industry continues to unlock new resources.”
How Assessments Started
USGS oil and gas assessments ramped up 50 years ago following the OPEC oil embargo against the U.S. in 1973.
“That signaled a need to understand the occurrence, distribution and potential volumes of undiscovered resources,” according to the USGS release. “The embargo led to a mandate for the USGS to use geologic science and data to assess undiscovered oil and gas resources to help meet the nation’s needs.”
“USGS energy assessments typically focus on undiscovered resources – areas where science tells us there may be a resource that industry hasn’t discovered yet,” stated Sarah Ryker, acting director of the USGS, in the March 13 press release. “In this case, after a century of production, the upper Paleozoic reservoirs of the Wind River, Bighorn and Powder River basins have little remaining undiscovered oil.”
Contact David Madison at david@cowboystatedaily.com
David Madison can be reached at david@cowboystatedaily.com.
