Monday, 9 March, 2026/Edition 101

Nearly 45 percent of U.S. crude oil production comes from the Permian Super Basin in Texas and New Mexico. Most of the producing reservoirs are Permian-age. The Wolfcamp Formation is perhaps the most well-known of these, but there are also little-tapped, deeper plays. This week, we will look at these lesser-known shale plays.

Rasoul Sorkhabi

Editor, Core Elements

Deeper Plays of Permian Super Basin

GB Hart/Shutterstock.com

The U.S. Geological Survey has released its latest report on undiscovered oil and gas resources in the Woodford and Barnett shales of the Permian Super Basin. Let’s take a look.

Where is the Permian? The Permian Super Basin includes the Delaware Basin to the west and the Midland Basin to the east, separated by Central High.

Woodford Shale stratigraphy:

• Devonian-age, organic-matter-rich bio-siliceous mudstone with quartzose content of 50–90 percent

• Deposited during a marine transgression across North America

• Maximum thickness is 300 feet with a variable porosity of up to 10 percent

USGS has defined the following assessment units for the Woodford Shale:

No. 1: Woodford Alpine High Continuous Gas

• Undiscovered resources (mean): 6,875 billion cubic feet of gas

• Undiscovered NGL resources (mean): 89 million barrels

No. 2: Woodford Delaware Basin Continuous Gas

• Undiscovered gas resources (mean): 7,520 billion cubic feet of gas

• Undiscovered NGL resources (mean): 75 million barrels

No. 3: Woodford Midland Basin Continuous Oil

• Undiscovered oil resources (mean): 701 million barrels

• Undiscovered gas resources (mean): 2,804 billion cubic feet of gas

• Undiscovered NGL resources (mean): 196 million barrels

No. 4: Woodford Central Basin Platform Continuous Oil

• Undiscovered oil resources (mean): 139 million barrels

• Undiscovered gas resources (mean): 577 billion cubic feet of gas

• Undiscovered NGL resources (mean): 39 million barrels

No. 5: Woodford Central Basin Platform Conventional Oil

• Undiscovered oil resources (mean): 3 million barrels of oil

• Undiscovered gas resources (mean): 13 billion cubic feet of gas

• Undiscovered NGL resources (mean): 1 million barrels

Barnett Shale stratigraphy:

• Middle to Late Mississippian age, organic-rich, mudstone that is rich in quartz and clay minerals

• Deposited in a deep marine basin in front of a large, rimmed carbonate platform

• Maximum thickness is 400 feet with a porosity of 3–6 percent

• After the Barnett deposition, the North American region switched from a passive continental margin to a continental collision between Laurentia and Gondwana during the Permian.

Barnett Shale oil and gas resources: USGS has defined the following assessment units for the Barnett Shale:

No. 1: Barnett Alpine High Continuous Gas

• Undiscovered resources (mean): 7,255 billion cubic feet of gas

• Undiscovered NGL resources (mean): 254 million barrels

No. 2: Barnett Delaware Basin Continuous Gas

• Undiscovered gas resources (mean): 1,672 billion cubic feet of gas

• Undiscovered NGL resources (mean): 50 million barrels

No. 3: Barnett Midland Basin Continuous Oil

• Undiscovered oil resources (mean): 660 million barrels

• Undiscovered gas resources (mean): 1,320 billion cubic feet of gas

• Undiscovered NGL resources (mean): 92 million barrels 

No. 4: Barnett Central Basin Platform Continuous Oil

• Undiscovered oil resources (mean): 122 million barrels

• Undiscovered gas resources (mean): 243 billion cubic feet of gas

• Undiscovered NGL resources (mean): 17 million barrels

Go deeper: Read the USGS report here.

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What’s in a Name: The Wolfcamp Formation and Wolfcampian Series

Wolfcamp stratigraphy (source: AAPG Bulletin)

The Wolfcamp Formation in the Permian Super Basin is one of the most prolific oil producers in the United States. However, the term “Wolfcamp Formation” is not officially recognized.

In the AAPG Bulletin, Wayne Camp recommends that this stratigraphic name be made official. In another publication, Spencer Lucas argues against it. Grab your popcorn for the debate!

The Wolfcamp Formation in the Glass Mountains:

• In 1917, J. A. Udden mapped and measured what he called the Wolfcamp Formation in West Texas’ Glass Mountains.

• The Wolcamp was named after an abandoned settlement near the Wolf Camp Hills on the southern flank of the Glass Mountains, which was frequently visited by wolves.

• The formation was measured to be 152 feet thick with more than 90 percent shale.

• The Wolfcamp Formation is sandwiched between the Gaptank Formation below and the Hess Formation above (later named the Leonard Formation).

• The U.S. Geological Survey recognized the term as a lithostratigraphic unit at that time.

Enter C. A. Ross:

• In 1959 and 1963, C. A. Ross revisited and studied the type locality but abandoned the term Wolfcamp.

• Instead, Ross suggested two new formations: The lower Neal Ranch Formation and the upper Lenox Hill Formation.

• The Neal Ranch and Lenox Hill formations are separated by an unconformity, and each contains distinctive fusulinid assemblages.

• These two formations were accepted by the US Geological Survey and are currently used in the stratigraphy of the Glass Mountains.

The Wolfcampian series:

• In 1939, J. A. Adams and colleagues suggested the use of the terms “Wolfcampian Series” and overlying “Leonardian Series” to represent the Lower Permian interval in North American stratigraphy.

• In the current International Stratigraphic Timescale, the Wolfcambrian Series and the Leonardian Series correspond to the Lower Permian Cisuralian Series (298–274 Ma).

• The Wolfcampian Series includes the Asselian, Sakmarian, and the lower part of the Artinskian stages.

• The Leonardian Series includes the upper part of the Artinskian and the overlying Kungurian stage.

Subsurface Wolfcamp Formation:

• In the Permian Super Basin, the time equivalent of Udden’s Wolfcamp formation has also been called the Wolfcamp Formation, but it is not officially recognized.

• Wayne Camp argues that the term Wolfcamp Formation should be reinstated as a lithostratigraphic unit and also recognized for the subsurface formation.

• He suggests the Ross Draw 7 well in New Mexico as the type well for the subsurface Wolfcamp Formation.

• He states that the term Wolfcamp is practically an established term, as it has been used in 322 papers between 1921 and 2023 in AAPG Bulletin and the Journal of Sedimentology.

Counterargument:

• Spencer Lucas argues against using the term Wolfcamp Formation but does not offer an alternative name.

• He states that the subsurface shale formation is deep marine while the outcrop formation is shallow marine.

• He supports the use of the term “Wolfcampian Series” as a chronostratigraphic unit in North American stratigraphy.

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