When you read about the oil and gas industry, certain names come up repeatedly: the Bakken, the Permian Basin, the Marcellus Shale. These are geologic formations, and the one your minerals sit above has a lot to do with what gets produced, how much it's worth, and how active the drilling is in your area.

What a Formation Is

A geologic formation is a distinct layer of rock with consistent characteristics. The formations that matter for oil and gas are the ones that contain hydrocarbons in commercially recoverable quantities. Each formation has its own depth, thickness, rock type, porosity, and the kind of hydrocarbons it holds.

Different formations underlie different parts of the country, and a single location may have multiple formations stacked at different depths.

Major U.S. Formations

Permian Basin (Texas, New Mexico)

The Permian Basin in West Texas and southeastern New Mexico is the most productive oil region in the United States. In 2024, it produced an average of 6.3 million barrels per day, accounting for 48% of total U.S. crude oil production. It contains multiple stacked formations (Wolfcamp, Bone Spring, Spraberry, and others) that allow operators to drill several wells at different depths from the same surface location. The Wolfcamp play alone produced 3.4 million barrels per day in 2024.

The Permian produces primarily oil with associated gas and NGLs. It has been drilled for over a century, but horizontal drilling and hydraulic fracturing unlocked massive additional reserves in the tight rock formations starting around 2010.

Bakken and Three Forks (North Dakota, Montana)

The Bakken formation in the Williston Basin of western North Dakota and eastern Montana was one of the first major shale plays developed with horizontal drilling. The Three Forks formation sits directly below the Bakken and is often drilled from the same pads.

The Bakken produces light sweet crude oil. North Dakota's production holds at roughly 1.1 to 1.2 million barrels per day, primarily from the Bakken. It made North Dakota one of the top oil-producing states and created significant wealth for mineral owners in McKenzie, Mountrail, Williams, and Dunn counties. For more on owning minerals there, see our North Dakota guide.

Marcellus Shale (Pennsylvania, West Virginia, Ohio)

The Marcellus Shale is the largest source of shale gas in the United States, accounting for roughly one-third of U.S. shale gas production. It underlies much of the Appalachian region and produces primarily dry gas (methane) in the northeast and wetter gas (with NGLs) in the southwest.

Development accelerated in the late 2000s and transformed Pennsylvania and West Virginia into major gas producers. For mineral owners, the Marcellus means gas royalties, which are more variable than oil royalties due to regional price differences. See our Pennsylvania guide for state-specific details.

SCOOP and STACK (Oklahoma)

The SCOOP (South Central Oklahoma Oil Province) and STACK (Sooner Trend, Anadarko Basin, Canadian and Kingfisher counties) are major plays in central Oklahoma targeting the Woodford Shale and Meramec formation. They produce a mix of oil, gas, and NGLs.

These formations brought a wave of horizontal drilling to Oklahoma starting around 2012. For Oklahoma mineral owners, activity in the SCOOP and STACK has driven lease bonuses, pooling orders, and royalty income. See our Oklahoma guide.

Eagle Ford (Texas)

The Eagle Ford Shale in South Texas produces oil, gas, and condensate in a band stretching from the Mexican border northeast toward East Texas. The oil window in the southwest is among the most productive in the country. The formation varies from oil-rich in the west to gas-rich in the east. Eagle Ford wells are known for steep first-year decline rates averaging around 70%.

Haynesville (Louisiana, Texas)

The Haynesville Shale in northwest Louisiana and East Texas is a deep, high-pressure gas formation. It was one of the first major shale gas plays but lost momentum when gas prices dropped. Activity has picked up in recent years as prices recovered, though production declined 12% in the first nine months of 2024 compared to the prior year.

Utica Shale (Ohio, Pennsylvania, West Virginia)

The Utica Shale lies beneath the Marcellus and is being developed in parts of eastern Ohio, western Pennsylvania, and northern West Virginia. It produces gas, condensate, and NGLs. In some areas, it's deeper and more pressured than the Marcellus, making wells more expensive but potentially more productive.

Niobrara (Colorado, Wyoming)

The Niobrara formation in the Denver-Julesburg Basin of northeastern Colorado and southeastern Wyoming produces oil and associated gas. It's a major play in Colorado and has driven significant drilling activity and regulatory debate in the state.

Why It Matters

The formation your minerals sit above determines:

When a landman contacts you about leasing, the formation they're targeting is the first thing to ask about. It tells you what kind of production to expect and what the economics look like.