By the USGS Wolfcamp Shale Assessment Team: Stephanie B. Gaswirth, Kristen R. Marra, Paul G. Lillis, Tracey J. Mercier, Heidi M. Leathers-Miller, Christopher J. Schenk, Timothy R. Klett, Phuong A. Le, Marilyn E. Tennyson, Sarah J. Hawkins, Michael E. Brownfield, Janet K. Pitman and Thomas M. Finn. USGS Fact Sheet 2016–3092, November 2016.
Using a geology-based method, the U.S. Geological Survey estimated a mean of 20 billion barrels of oil and 16 trillion cubic feet of gas — undiscovered, technically recoverable — in the Wolfcamp shale of the Midland Basin, part of the Permian Basin Province of west Texas.
The Midland Basin and the six Wolfcamp assessment units. Base: National Park Service. Map: USGS.
A first look at the Wolfcamp
This 2016 assessment was the USGS's first of continuous resources in the Midland Basin's Wolfcamp shale (an informal name, for rocks of Pennsylvanian–Permian age).
- The old way: since the 1980s the Wolfcamp has been part of the "Wolfberry" play, tapped by vertical wells completed in several zones, including the Wolfcamp and the overlying Spraberry Formation.
- The new way: horizontal wells, hydraulically fractured, target the Wolfcamp for continuous oil; more than 3,000 had been drilled and completed.
The geology
The Permian Basin of west Texas and southeastern New Mexico has two sub-basins, the Delaware to the west and the Midland to the east, split by the uplifted Central Basin Platform.
- On the platforms: during the Pennsylvanian–Permian, the Wolfcamp was laid down as shallow-water carbonates on the Central Basin Platform and Eastern Shelf.
- In the basin: deeper water collected organic-rich mud interbedded with clay-rich mud and fine carbonates.
- Mature: throughout the region, the shale is mature for oil generation.
- Four units: industry splits it by log signatures and landing zones into Wolfcamp A (top), B, C and D. The basin's eastern edge built westward over time, so units C and D cover more ground than A and B.
Six assessment units
All within the Permian Basin Paleozoic Composite Total Petroleum System:
| Unit | Bounded by |
|---|---|
| Wolfcamp A and B Upper | Central Basin Platform (west); Horseshoe atoll and thick Wolfcamp strata (north); Eastern Shelf margin (east); the Val Verde Basin Canyon Sandstone unit (south) |
| Wolfcamp B Lower | the southern basin, where the B is more than 500 feet thick — room for two lateral wells |
| Wolfcamp C | as A, with the eastern edge set by the C's mapped depositional limit |
| Wolfcamp D | as A, with the Upper Pennsylvanian shale limit to the northeast and east |
| Northern Wolfcamp | the basin's shelf margin (north and east) and the thick strata to the south |
The results
Fully risked means, all with AU probability 1.0. F95 means a 95 percent chance of at least that amount.
| Unit | Oil mean (MMBO) | Oil F95–F5 | Gas mean (BCFG) | NGL mean (MMBNGL) |
|---|---|---|---|---|
| Wolfcamp A | 5,815 | 3,754–8,483 | 4,652 | 465 |
| Wolfcamp B Upper | 5,829 | 3,769–8,505 | 4,663 | 466 |
| Wolfcamp B Lower | 1,430 | 794–2,351 | 1,144 | 114 |
| Wolfcamp C | 1,433 | 577–2,728 | 1,146 | 115 |
| Wolfcamp D | 4,920 | 2,420–8,262 | 3,936 | 394 |
| Northern Wolfcamp | 521 | 116–1,139 | 417 | 42 |
| Total | 19,948 | 11,430–31,468 | 15,958 | 1,596 |
MMBO: million barrels of oil. BCFG: billion cubic feet of associated gas. MMBNGL: million barrels of natural gas liquids.
- Oil: 19,948 million barrels, about 20 billion.
- Gas: 15,958 billion cubic feet of associated gas (about 16 trillion), ranging 7,887 to 27,310.
- Liquids: 1,596 million barrels, ranging 698 to 2,926.
A pumpjack in rural Texas. Photograph from the Carol M. Highsmith Archive, Library of Congress.
More assessments: the USGS Energy Resources Program.
Sources
Based on Assessment of Undiscovered Continuous Oil Resources in the Wolfcamp Shale of the Midland Basin, Permian Basin Province, Texas, 2016, USGS Fact Sheet 2016–3092, U.S. Geological Survey; a work of the United States government in the public domain. The map, the results table and the pumpjack photograph are taken from the fact sheet's PDF; a road photograph used with permission from the Texas Historical Commission is not reproduced.
Licence: CC0 1.0 (public domain) · Adapted from pubs.usgs.gov
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