Figure 1. Permian Basin 

Province in west Texas and 

southeastern New Mexico. The 

Permian Basin Province contains 

the Midland Basin, Delaware 

Basin, Pecos Basin, Central Basin 

Platform, Val Verde Basin, Ozona 

Arch, and the Northwestern, 

Northern, and Eastern Shelves.

Using a geology-based assessment 

methodology, the U.S. Geological Survey 

estimated a mean of 41 trillion cubic feet 

of undiscovered natural gas and a mean of 

1.3 billion barrels of undiscovered oil in 

the Permian Basin Province.

0 50 100 Miles

Permian Basin

Province

Paleozoic Composite TPS

Northern Shelf

Eastern

Shelf

Ozona

Arch

Val Verde

Marathon Fold Basin

and Thrust Belt

Pecos

 Basin

MEXICO

NEW MEXICO TEXAS

UNITED

STATES

Northwestern Shelf

Delaware 

Basin

Central

 Basin

 Platform

Midland 

Basin

106° 105° 104° 103° 102° 101° 100° 99°

34°

33°

32°

31°

30°

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2007–3115

February 2008 Printed on recycled paper

National Assessment of Oil and Gas Fact Sheet

Assessment of Undiscovered Oil and Gas Resources of the 

Permian Basin Province of West Texas and Southeast

New Mexico, 2007

Introduction

The U.S. Geological Survey (USGS) recently assessed 

the undiscovered oil and gas potential of the Permian 

Basin Province of west Texas and southeast New Mexico 

(figs. 1, 2). The assessment was geology based and used the 

total petroleum system (TPS) concept. The geologic elements 

of a total petroleum system are petroleum source rocks (quality, 

source rock maturation, generation, and migration), reservoir 

rocks (sequence stratigraphy, petrophysical properties), and traps 

(trap formation and timing). Using this geologic framework, the 

USGS defined a Paleozoic Composite Total Petroleum System and 

31 assessment units (AU) within the system, and it quantitatively 

estimated the undiscovered oil and gas resources within 30 of the 

assessment units (table 1). This study assessed potential for technically recoverable resources in new field discoveries only; field 

growth (or reserve growth) of conventional oil and gas fields was 

not included.

Each of the 26 conventional oil and gas assessment units 

in this study is geologically comparable to one or more oil and 

gas plays that were defined in the Permian Basin Province by the 

Bureau of Economic Geology, Texas, and the New Mexico Bureau 

of Geology and Mineral 

Resources (Broadhead, 

1993; Dutton and others, 

2005). Some oil and gas 

plays were combined to 

form a single assessment 

unit.

For the first time, the 

USGS defined continuous 

(unconventional) assessment units in the Permian 

Basin Province. These units 

were the (1) Spraberry 

Continuous Oil AU; (2) 

Woodford–Barnett Continuous Gas AU; (3) Delaware–

Pecos Basins Woodford 

Continuous Shale Gas AU; 

(4) Delaware–Pecos Basins 

Barnett Continuous Gas 

Shale AU; and (5) Delaware 

Basin Wolfcamp Shale AU.
Figure 2. Photograph of the Guadalupe Mountains in west Texas illustrating the massive El Capitan carbonate fore-reef facies and the underlying slope-forming Delaware 

Mountain Group sandstones and mudstones.

Resource Summary

The USGS assessed undiscovered conventional oil and gas resources and continuous (unconventional) oil and gas resources in 30 

assessment units (table 1). For conventional resources, the estimated means were 747 million barrels of oil (MMBO), 5.2 trillion cubic 

feet of gas (TCFG), and 236 million barrels of natural gas liquids (MMBNGL) in 26 assessment units. 

For continuous gas resources, the USGS estimated a total mean resource of 34.8 TCFG in three assessment units, which comprises a mean of 2.8 TCFG in the Woodford–Barnett Continuous Gas AU of the Midland Basin, a mean of 15 TCFG in the Delaware–

Pecos Basins Woodford Continuous Shale Gas AU, and a mean of 17 TCFG in the Delaware–Pecos Basins Barnett Continuous Gas 

Shale AU in the Delaware Basin. The Delaware Basin Wolfcamp Shale AU was not assessed. For continuous oil resources the estimated mean was 510 MMBO in the Spraberry Continuous Oil AU in the Midland Basin.

The assessment indicates that the majority of undiscovered natural gas in the Permian Basin Province is estimated to be in three 

continuous assessment units of the Delaware and Midland Basins. Of the total mean of 41 TCFG in the province, about 35 TCFG is 

estimated to be in these three assessment units. Given that few wells have produced from these assessment units, there is significant 

geologic uncertainty in these estimates, which is reflected in the range of estimates for natural gas (table 1).

For Further Information

Supporting geologic studies of the composite total petroleum system and assessment units and the methodology used in the 

Permian Basin Province assessment are in progress. Assessment results are available at the USGS Central Energy Team website, 

http://energy.cr.usgs.gov/oilgas/noga.
Total Petroleum System

(TPS) 

and Assessment Unit (AU)

Field 

Type

Total Undiscovered Resources

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

Paleozoic Composite TPS

Ellenberger Group Karst 

and Dolomite AU

Oil 12 40 83 43 12 40 90 44 1 3 8 4

Gas 147 475 924 498 3 11 24 12

Simpson Group 

Sandstones AU

Oil 1 3 6 3 2 6 14 7 0 0 1 0

Gas 22 63 123 66 1 2 5 2

Pre-Pennsylvanian Ramp and 

Platform Carbonates AU

Oil 15 48 95 51 17 56 122 61 1 4 10 5

Gas 91 323 664 343 3 12 28 14

Devonian Thirtyone Formation 

Chert and Carbonate AU

Oil 7 22 45 24 23 79 178 87 2 8 19 9

Gas 91 321 665 344 5 17 38 19

Lower Pennsylvanian 

(Morrow/Atoka) Shelf 

Sandstone and Carbonate AU

Oil 0 0 0 0 0 0 0 0 0 0 0 0

Gas 238 780 1,485 812 3 9 19 10

Pennsylvanian–Lower Permian 

(Wolfcamp) Northwest Shelf 

Carbonate AU

Oil 8 27 56 29 21 72 161 79 1 5 11 5

Gas 43 146 308 158 1 4 9 4

Pennsylvanian–Lower Permian 

(Wolfcamp) Central Basin Platform and Shelf Carbonate AU

Oil 12 40 79 42 43 150 330 164 3 10 24 11

Gas 57 183 355 192 3 9 18 9

Pennsylvanian–Lower Permian 

(Wolfcamp) Horseshoe Platform and Eastern Shelf 

Carbonate and Sandstone AU

Oil 28 93 175 96 42 143 299 154 5 17 38 18

Gas 15 38 69 40 0 1 3 1

Pennsylvanian–Lower Permian 

(Wolfcamp) Val Verde Slope 

and Basinal Sandstone and 

Carbonate AU

Oil 3 9 22 10 16 56 139 64 1 3 9 4

Gas 183 702 1,517 758 8 31 74 35

Pennsylvanian–Lower Permian 

(Wolfcamp) Slope and Basinal 

Carbonates AU

Oil 3 12 27 13 9 32 83 37 0 2 5 2

Gas 62 222 481 241 2 9 20 10

Abo Fluvial Sandstones AU

Oil 0 0 0 0 0 0 0 0 0 0 0 0

Gas 0 0 23 8 0 0 0 0

Abo Shelf and Shelf Edge 

Carbonates AU

Oil 11 39 83 42 23 83 194 93 2 6 15 7

Gas 25 65 123 69 1 2 5 3

Leonardian NW and E Shelf 

Restricted Platform Carbonates 

AU

Oil 22 74 146 78 16 57 125 62 1 4 10 5

Gas 0 0 0 0 0 0 0 0

Leonardian Central Basin Platform Restricted Carbonates AU

Oil 10 31 61 33 29 96 209 105 2 7 16 8

Gas 13 33 62 35 1 1 3 2

Leonardian Midland Basin 

Carbonate Sediment Gravity 

Flow Reservoirs AU

Oil 28 93 185 98 47 161 355 176 3 10 25 12

Gas 0 0 0 0 0 0 0 0

Bone Spring Slope and Basin 

Reservoirs AU

Oil 15 50 100 53 55 192 423 210 2 9 21 10

Gas 0 0 0 0 0 0 0 0

Spraberry Conventional 

Sandstones AU

Oil 5 18 43 20 4 14 36 16 0 1 4 2

Gas 0 0 0 0 0 0 0 0

San Andres NW Shelf Platform 

Carbonates AU

Oil 2 5 8 5 2 4 8 4 0 0 1 0

Gas 0 0 0 0 0 0 0 0

San Andres Eastern Shelf 

Platform Carbonates AU

Oil 0 0 3 1 0 0 1 0 0 0 0 0

Gas 0 0 0 0 0 0 0 0

Conventional Oil and Gas Resources

[MMBO, million barrels of oil. BCFG, billion cubic feet of gas. MMBNGL, million barrels of natural gas liquids. Results shown are fully risked estimates. For gas 

accumulations, all liquids are included as NGL (natural gas liquids). F95 represents a 95 percent chance of at least the amount tabulated; other fractiles are 

defined similarly. TPS, total petroleum system; AU, assessment unit. Gray shading indicates not applicable]

Table 1. Permian Basin Province assessment results.
Total Petroleum System 

(TPS) 

and Assessment Unit (AU)

Field 

Type

Total Undiscovered Resources

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

Paleozoic Composite TPS—Continued

San Andres Central Basin 

Platform Carbonates AU

Oil 5 17 33 18 8 25 53 27 1 2 6 3

Gas 0 0 0 0 0 0 0 0

San Andres–Grayburg Lowstand Carbonates AU

Oil 3 8 16 9 1 2 5 3 0 0 1 0

Gas 0 0 0 0 0 0 0 0

San Andres–Grayburg ArtesiaVacuum Trend Carbonates AU

Oil 0 2 5 2 0 3 8 3 0 0 0 0

Gas 0 0 0 0 0 0 0 0

Grayburg Central Basin Platform 

and Ozona Arch Carbonates AU

Oil 0 1 3 1 0 0 4 1 0 0 0 0

Gas 0 4 21 7 0 0 1 0

Delaware Mountain Group 

Reservoirs AU

Oil 18 64 134 69 37 137 314 152 2 6 15 7

Gas 8 17 31 18 0 1 1 1

Queen Sandstones AU

Oil 2 6 11 6 2 6 12 6 0 0 1 0

Gas 17 42 73 43 1 1 3 2

Upper Artesia Sandstones and 

Carbonates AU

Oil 0 0 3 1 0 0 6 2 0 0 0 0

Gas 0 0 20 7 0 0 1 0

Total Conventional

 Resources 747 5,196 236

Delaware-Pecos Basins Woodford Continuous Shale Gas AU

Oil 0 0 0 0 0 0 0 0 0 0 0 0

Gas 10,249 14,741 21,203 15,105 177 289 473 302

Delaware-Pecos Basins Barnett Continuous Shale Gas AU

Oil 0 0 0 0 0 0 0 0 0 0 0 0

Gas 1,008 16,437 26,698 17,203 177 322 585 344

Midland Basin WoodfordBarnett Continuous Gas AU

Oil 0 0 0 0 0 0 0 0 0 0 0 0

Gas 1,546 2,670 4,613 2,822 55 105 198 113 

Delaware Basin Wolfcamp 

Shale AU

Oil

Gas

Spraberry Continuous Oil AU

Oil 340 497 725 510 127 240 453 258 11 24 48 26

Gas 0 0 0 0 0 0 0 0

Total Continuous

 Resources 510 35,388 785

Total Undiscovered 

 Oil and Gas Resources 1,257 40,584 1,021

Conventional Oil and Gas Resources Continuous Oil and Gas Resources

Not quantitatively assessed

Table 1. Permian Basin Province assessment results.—Continued

References

Broadhead, R.F., 1993, Permian Basin Permian [PB] plays—Overview, in Robertson, J.M., and Broadhead, R.F., eds., Atlas of major 

Rocky Mountain gas reservoirs: New Mexico Bureau of Mines and Mineral Resources, p. 138–153.

Dutton, S.P., Kim, E.M., Broadhead, R.F., Raatz, W.D., Breton, C.L., Ruppel, S.C., and Kerans, C., 2005, Play analysis and leadingedge oil-reservoir development methods in the Permian Basin—Increased recovery through advanced technologies: American 

Association of Petroleum Geologists Bulletin, v. 89, no. 5, p. 553–576.

Permian Basin Province Assessment Team

Christopher J. Schenk, Richard M. Pollastro, Troy A. Cook, Mark J. Pawlewicz, Timothy R. Klett, Ronald R. Charpentier, and 

Harry E. Cook.