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By the USGS Spraberry Formation Assessment Team: Kristen R. Marra, Stephanie B. Gaswirth, Christopher J. Schenk, Heidi M. Leathers-Miller, Timothy R. Klett, Tracey J. Mercier, Phuong A. Le, Marilyn E. Tennyson, Thomas M. Finn, Sarah J. Hawkins and Michael E. Brownfield
Using a geology-based method, the U.S. Geological Survey estimated undiscovered, technically recoverable oil and gas in the Spraberry Formation of the Midland Basin, in the Permian Basin Province of west Texas: a mean of 4.2 billion barrels of oil and 3.1 trillion cubic feet of gas.
Key geologic features and the Spraberry assessment units (AUs). USGS.
Why a new look
The Spraberry was long drilled with vertical wells. Ever-deeper wells and perforations in the Spraberry and the Wolfcamp shale beneath it created the informal "Wolfberry" play across the Spraberry (trend area) field (Hamlin and Baumgardner, 2012; Railroad Commission of Texas, 2014). The formation was last assessed in 2007, from vertical-well history (Schenk and others, 2007); since then, several of its intervals have been targeted with horizontal drilling.
The rocks
The Lower Permian (Leonardian) Spraberry is interbedded sandstone, siltstone, carbonate and organic-rich shale, laid down in deep water in the Midland Basin — the eastern subbasin of the Permian Basin, rimmed by carbonate platforms: the Central Basin platform, Eastern shelf and Northern shelf. It is informally split into upper, middle and lower intervals (Hamlin and Baumgardner, 2012).
- South: production from continuous reservoirs is widespread across the Spraberry (trend area) field.
- North: conventional production comes from separate fields in several Spraberry intervals and the underlying Dean Formation.
Three assessment units
All lie within the Permian Basin Paleozoic Composite Total Petroleum System (Schenk and others, 2007; Gaswirth and others, 2016).
| AU | Covers |
|---|---|
| Middle Spraberry Continuous Oil Trend | the informal middle Spraberry |
| Lower Spraberry Continuous Oil Trend | the informal lower Spraberry, including the industry's lower Spraberry shale and Jo Mill siltstone |
| Northern Spraberry Conventional Oil | the whole Spraberry across the Horseshoe atoll and the basin's north, bounded by the shelf margins to the north and east and by the extent of drilling to the west |
The two continuous units share one area: the Central Basin platform to the west, the Eastern shelf margin to the east, roughly the southern edge of the Horseshoe atoll to the north, and the Val Verde Basin to the south (Schenk and others, 2016).
The estimates
For the three units, mean estimates:
- Oil: 4,245 million barrels — about 4.2 billion (F95–F5 range 1,873 to 7,635).
- Gas: 3,112 billion cubic feet — about 3.1 trillion cubic feet (1,080 to 6,200).
- Natural gas liquids: 311 million barrels (100 to 652).
F95 means a 95-percent chance of at least that much; F5, a 5-percent chance.
| AU | Oil, mean (million barrels) | Gas, mean (billion cubic feet) |
|---|---|---|
| Lower Spraberry (continuous) | 2,793 | 2,048 |
| Middle Spraberry (continuous) | 1,447 | 1,061 |
| Northern Spraberry (conventional) | 5 (3–10) | 3 (1–5) |
Nearly all of it is in the continuous units.
More: USGS Energy Resources Program.
Sources
Based on Assessment of Undiscovered Oil and Gas Resources in the Spraberry Formation of the Midland Basin, Permian Basin Province, Texas, 2017, by the Spraberry Formation Assessment Team, USGS Fact Sheet 2017–3029, U.S. Geological Survey; a work of the United States government in the public domain. The map and the results for the two continuous units are taken from the fact sheet's PDF, which the import had left out.
Лицензия: CC0 1.0 (общественное достояние) · По материалам pubs.usgs.gov
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