National and Global Petroleum Assessment

Assessment of Undiscovered Continuous Oil and Gas Resources in 

the Wolfcamp Shale and Bone Spring Formation of the Delaware 

Basin, Permian Basin Province, New Mexico and Texas, 2018

Introduction

In 2018, the U.S. Geological Survey (USGS) completed a 

geology-based assessment of undiscovered, technically recoverable continuous oil and gas resources in the Pennsylvanian–

Permian Wolfcamp shale (informal name; age follows Hamlin 

and Baumgardner, 2012) and the early Permian Bone Spring 

Formation of the Delaware Basin in the Permian Basin Province, southeast New Mexico and west Texas (figs. 1–3). The 

Delaware Basin is the western subbasin of the Permian Basin 

Province and is separated from the eastern Midland Basin by 

the uplifted Central Basin Platform. The Delaware Basin is 

rimmed by carbonate platforms, including the Central Basin 

and Diablo Platforms and the Northwest Shelf. The Wolfcamp 

shale was deposited throughout the Permian Basin and consists 

of interbedded, organic-rich shales and carbonates in both the 

Midland and Delaware Basins; however, the Wolfcamp shale 

in the Delaware Basin is thicker, deeper, and more thermally 

mature than in the Midland Basin. The overlying Bone Spring 

consists of alternating sandstone, carbonate, and shale cycles 

and is time-equivalent to the Spraberry Formation in the 

Midland Basin. 

Recent USGS assessments of continuous oil and gas 

resources in the Permian Basin Province include the Wolfcamp 

shale (Gaswirth and others, 2016) and the Spraberry Formation 

(Marra and others, 2017) in the Midland Basin. The Bone Spring 

Formation was assessed for conventional oil and gas resources in 

2007 (Schenk and others, 2008).

This is the first USGS assessment of continuous 

resources in the Wolfcamp shale and Bone Spring Formation of the Delaware Basin. Both the Wolfcamp shale and 

the Bone Spring Formation are subdivided into stratigraphic 

units based on petrophysical log signatures and landing 

zones for horizontal wells. This assessment used data from 

the EnerdeqTM and ProdFitTM databases (IHS Markit®, 

2018a, b) for information on well landing zones, well 

production, and unit depths and thicknesses. Figure 1. Map showing the Delaware Basin, Permian Basin 

Province, New Mexico and Texas, and the extent of the two 

Wolfcamp shale-gas continuous assessment units (AUs). Province 

boundary is from Klett and others, 1997.

Base map from U.S. Department of the Interior National Park Service

Diablo Platform

Northwest Shelf

Central Basin Platform

NEW MEXICO

TEXAS

YOAKUM

LINCOLN

EDDY LEA

HUDSPETH

GAINES

ECTOR

OTERO

CHAVES

LOVING

CRANE

CULBERSON

TERRY

WARD

WINKLER

JEFF DAVIS

ANDREWS

REEVES

BREWSTER

PECOS

TERRELL

PRESIDIO

UNITED STATES

MEXICO

Permian Basin Province boundary

is shown in plum.

TX

MEXICO

NM

OK

AZ

CO KS

AR

LA

UT MO

GULF OF

MEXICO

Map

area

0 15 30 KILOMETERS

0 15 30 MILES

31°

32°

105°

33°

104° 103°

EXPLANATION

Delaware Basin Wolfcamp C Continuous 

 Gas AU

Permian Basin Province boundary (part)

Delaware Basin Wolfcamp D Continuous 

 Gas AU

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2018–3073 

December 2018

Using a geology-based assessment methodology, the U.S. Geological Survey assessed undiscovered, technically recoverable continuous mean resources of 46.3 billion barrels of oil and 281 trillion cubic feet of gas in the Wolfcamp shale and 

Bone Spring Formation of the Delaware Basin in the Permian Basin Province, southeast New Mexico and west Texas.
Figure 2. Map showing the Delaware Basin, Permian Basin 

Province, New Mexico and Texas, and the extent of the four 

Wolfcamp shale-oil continuous assessment units (AUs). Province 

boundary is from Klett and others, 1997.

Figure 3. Map showing the Delaware Basin, Permian Basin 

Province, New Mexico and Texas, and the extent of the five Bone 

Spring Formation continuous assessment units (AUs). The Third, 

Second, and First Bone Spring AUs have the same extent. Province 

boundary is from Klett and others, 1997.

Definition of Assessment Units

Eleven continuous assessment units (AUs) were defined 

and quantitatively assessed in the Wolfcamp shale and the Bone 

Spring Formation of the Delaware Basin in the Permian Basin 

Province, southeast New Mexico and west Texas. Six are in the 

Pennsylvanian–Permian Wolfcamp shale, and five are in the Permian Bone Spring Formation. The AUs are all within the Permian 

Basin Paleozoic Composite Total Petroleum System (Schenk 

and others, 2008) and are as follows, from oldest to youngest in 

age: (1) Delaware Basin Wolfcamp D Continuous Gas AU, (2) 

Delaware Basin Wolfcamp C Continuous Gas AU, (3) Delaware 

Basin Wolfcamp C Continuous Oil AU, (4) Delaware Basin Wolfcamp B Lower Continuous Oil AU, (5) Delaware Basin Wolfcamp 

B Upper Continuous Oil AU, (6) Delaware Basin Wolfcamp A 

Continuous Oil AU, (7) Third Bone Spring Continuous Oil AU, 

(8) Second Bone Spring Continuous Oil AU, (9) First Bone Spring 

Continuous Oil AU, (10) Lower Avalon Shale Continuous Oil AU, 

and (11) Upper Avalon Shale Continuous Oil AU.

Assessment unit boundaries are constrained by the 

Delaware Basin boundary, as defined by Dutton and others 

(2005) and Hamlin and Baumgardner (2012); extent of basinal 

facies; thermal maturation data (Pawlewicz and others, 2005); 

one-dimensional burial history modeling; isopach thickness of 

individual units; and structural top data (IHS Markit, 2018b). 

Assessment input data for the 11 AUs are summarized in table 1. 

Undiscovered Resources Summary

The USGS quantitatively assessed undiscovered, technically recoverable continuous oil and gas resources for 

six AUs in the Wolfcamp shale and five AUs in the Bone 

Spring Formation (table 2) of the Delaware Basin of the 

Permian Basin Province. Estimated mean resources are 

46,271 million barrels of oil (MMBO), or 46.3 billion barrels 

of oil, with an F95–F5 range from 26,729 to 71,075 MMBO; 

280,630 billion cubic feet of gas (BCFG), or 281 trillion cubic 

feet of associated gas, with an F95–F5 range from 108,583 

to 490,074 BCFG; and 19,917 million barrels of natural gas 

liquids (MMBNGL) with an F95–F5 range from 7,417 to 

37,349 MMBNGL (table 2).

Base map from U.S. Department of the Interior National Park Service

Diablo Platform

Northwest Shelf

Central Basin Platform

NEW MEXICO

TEXAS

YOAKUM

LINCOLN

EDDY LEA

HUDSPETH

GAINES

ECTOR

OTERO

CHAVES

LOVING

CRANE

CULBERSON

TERRY

WARD

WINKLER

JEFF DAVIS

ANDREWS

REEVES

BREWSTER

PECOS

PRESIDIO

UNITED STATES

MEXICO

TERRELL

31°

32°

105°

33°

104° 103°

EXPLANATION

Delaware Basin Wolfcamp B Lower Continuous 

 Oil AU

Delaware Basin Wolfcamp B Upper Continuous 

 Oil AU

Delaware Basin Wolfcamp C Continuous Oil AU

Permian Basin Province boundary (part)

Delaware Basin Wolfcamp A Continuous Oil AU

Permian Basin Province boundary

is shown in plum.

TX

MEXICO

NM

OK

AZ

CO KS

AR

LA

UT MO

GULF OF

MEXICO

Map

area

0 15 30 KILOMETERS

0 15 30 MILES

Base map from U.S. Department of the Interior National Park Service

Diablo Platform

Northwest Shelf

Central Basin Platform NEW MEXICO TEXAS YOAKUM

LINCOLN

EDDY LEA

HUDSPETH

GAINES

ECTOR

OTERO

CHAVES

LOVING

CRANE

CULBERSON

TERRY

WARD

WINKLER

JEFF DAVIS

ANDREWS

REEVES

BREWSTER

PECOS

PRESIDIO

UNITED STATES

MEXICO

TERRELL

32°

105°

33°

104° 103°

31°

EXPLANATION

Second Bone Spring Continuous 

 Oil AU

Third Bone Spring Continuous 

 Oil AU

Permian Basin Province 

 boundary (part)

First Bone Spring Continuous 

 Oil AU

Lower Avalon Shale Continuous 

 Oil AU

Upper Avalon Shale Continuous 

 Oil AU
Table 1. Key input data for 11 continuous assessment units (AUs) in the Wolfcamp shale and Bone Spring Formation of the Delaware Basin, 

Permian Basin Province, New Mexico and Texas. 

[AU, assessment unit; %, percent; EUR, estimated ultimate recovery per well; MMBO, million barrels of oil; BCFG, billion cubic feet of gas. Well drainage area, success ratio, and EUR are defined partly using U.S. shale-gas and shale-oil analogs. The average EUR input is the minimum, median, maximum, and calculated mean. 

Shading indicates not applicable]

Assessment input data—

Continuous AUs

Delaware Basin Wolfcamp D Continuous Gas AU Delaware Basin Wolfcamp C Continuous Gas AU

Minimum Mode Maximum Calculated 

mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 2,000 5,100,000 7,100,000 4,067,333 1,500 3,000,000 4,400,000 2,467,167

Average drainage area of wells (acres) 80 100 160 113.3 80 100 160 113.3

Area untested in AU (%) 97 98 99 98 95 98 99 97.3

Success ratio (%) 70 80 90 80.0 50 70 90 70

Average EUR (BCFG) 1.0 2.5 4.5 2.579 1.0 2.5 4.5 2.579

AU probability 1.0 1.0

Assessment input data—

Continuous AU

Delaware Basin Wolfcamp C Continuous Oil AU Delaware Basin Wolfcamp B Lower Continuous Oil AU

Minimum Mode Maximum Calculated 

mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 1,000 2,500,000 3,300,000 1,933,667 1,000,000 3,800,000 4,500,000 3,100,000

Average drainage area of wells (acres) 60 80 160 100 60 80 160 100

Area untested in AU (%) 100 100 100 100 91 97 98 95.3

Success ratio (%) 10 50 90 50 90 95 99 94.7

Average EUR (MMBO) 0.01 0.16 0.35 0.167 0.1 0.18 0.4 0.191

AU probability 1.0 1.0

Assessment input data—

Continuous AU

Delaware Basin Wolfcamp B Upper Continuous Oil AU Delaware Basin Wolfcamp A Continuous Oil AU

Minimum Mode Maximum Calculated 

mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 1,800,000 5,600,000 7,750,000 5,050,000 4,000,000 5,600,000 7,600,000 5,733,333

Average drainage area of wells (acres) 60 80 160 100 60 80 160 100

Area untested in AU (%) 95 98 99 97.3 92 95 96 94.3

Success ratio (%) 90 95 99 94.7 90 95 99 94.7

Average EUR (MMBO) 0.12 0.18 0.4 0.192 0.14 0.24 0.5 0.253

AU probability 1.0 1.0

Assessment input data—

Continuous AU

Third Bone Spring Continuous Oil AU Second Bone Spring Continuous Oil AU

Minimum Mode Maximum Calculated 

mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 4,000,000 5,000,000 5,600,000 4,866,667 3,600,000 5,000,000 5,600,000 4,733,333

Average drainage area of wells (acres) 120 160 180 153.3 120 160 180 153.3

Area untested in AU (%) 96 97 98 97 95 96 97 96

Success ratio (%) 90 95 99 94.7 90 95 99 94.7

Average EUR (MMBO) 0.14 0.22 0.45 0.232 0.1 0.18 0.3 0.185

AU probability 1.0 1.0

Assessment input data—

Continuous AU

First Bone Spring Continuous Oil AU Lower Avalon Shale Continuous Oil AU

Minimum Mode Maximum Calculated 

mean Minimum Mode Maximum Calculated mean

Potential production area of AU (acres) 2,000 3,500,000 5,600,000 3,034,000 400,000 1,400,000 3,000,000 1,600,000

Average drainage area of wells (acres) 120 160 180 153.3 80 120 160 120

Area untested in AU (%) 97 98 99 98 91 95 97 94.3

Success ratio (%) 70 80 90 80 70 80 90 80

Average EUR (MMBO) 0.1 0.13 0.25 0.137 0.05 0.11 0.2 0.114

AU probability 1.0 1.0

Assessment input data—

Continuous AU

Upper Avalon Shale Continuous Oil AU

Minimum Mode Maximum Calculated 

mean

Potential production area of AU (acres) 500,000 2,500,000 3,600,000 2,200,000

Average drainage area of wells (acres) 80 120 160 120

Area untested in AU (%) 93 96 97 95.3

Success ratio (%) 70 80 90 80

Average EUR (MMBO) 0.05 0.11 0.2 0.114

AU probability 1.0
For More Information

Assessment results are also available at the USGS Energy Resources Program website at https://energy.usgs.gov.

Delaware Basin Continuous Resources Assessment Team

Stephanie B. Gaswirth, Katherine L. French, Janet K. Pitman, Kristen R. Marra, Tracey J. Mercier, Heidi M. Leathers-Miller, 

Christopher J. Schenk, Marilyn E. Tennyson, Cheryl A. Woodall, Michael E. Brownfield, Thomas M. Finn, and Phuong A. Le

References Cited

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 

leading-edge 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.

Gaswirth, S.B., Marra, K.R., Lillis, P.G., Mercier, T.J., LeathersMiller, H.M., Schenk, C.J., Klett, T.R., Le, P.A., Tennyson, M.E., 

Hawkins, S.J., Brownfield, M.E., Pitman, J.K., and Finn, T.M., 

2016, Assessment of undiscovered continuous oil resources in the 

Wolfcamp shale of the Midland Basin, Permian Basin Province, 

Texas, 2016: U.S. Geological Survey Fact Sheet 2016–3092, 4 p.

Hamlin, H.S., and Baumgardner, R.W., 2012, Wolfberry 

(Wolfcampian-Leonardian) deep-water depositional systems 

in the Midland Basin—Stratigraphy, lithofacies, reservoirs, 

and source rocks: The University of Texas at Austin, Bureau of 

Economic Geology, Report of Investigations No. 277, 61 p.

IHS Markit®, 2018a, EnerdeqTM US well history and production 

database: Englewood, Colo., IHS Markit, accessed April 2018 

at http://www.ihsenergy.com. [Available from IHS Markit, 

15 Inverness Way East, Englewood, CO 80112.]

IHS Markit®, 2018b, PRODFitTM database: Englewood, Colo., IHS 

Markit, accessed May 2018 at http://www.ihsenergy.com. [Available 

from IHS Markit, 15 Inverness Way East, Englewood, CO 80112.]

Klett, T.R., Ahlbrandt, T.S., Schmoker, J.W., and Dolton, G.L., 1997, 

Ranking of the world’s oil and gas provinces by known petroleum volumes: U.S. Geological Survey Open-File Report 97–463, 

1 CD–ROM. [Also available at https://pubs.usgs.gov/of/1997/

ofr-97-463/97463.html.]

Marra, K.R., Gaswirth, S.B., Schenk, C.J., Leathers-Miller, H.M., 

Klett, T.R., Mercier, T.J., Le, P.A., Tennyson, M.E., Finn, T.M., 

Hawkins, S.J., and Brownfield, M.E., 2017, Assessment of 

undiscovered oil and gas resources in the Spraberry Formation of 

the Midland Basin, Permian Basin Province, Texas, 2017: U.S. 

Geological Survey Fact Sheet 2017–3029, 2 p.

Pawlewicz, M., Barker, C.E., and McDonald, S., 2005, Vitrinite reflectance data for the Permian Basin, west Texas and southeast New 

Mexico: U.S. Geological Survey Open-File Report 2005–1171, 25 p.

Schenk, C.J., Pollastro, R.M., Cook, T.A., Pawlewicz, M.J., Klett, 

T.R., Charpentier, R.R., and Cook, H.E., 2008, Assessment of 

undiscovered oil and gas resources of the Permian Basin Province 

of west Texas and southeast New Mexico, 2007: U.S. Geological 

Survey Fact Sheet 2007–3115, 4 p.

Table 2. Results for 11 continuous assessment units (AUs) in the Wolfcamp shale and Bone Spring Formation of the Delaware Basin, 

Permian Basin Province, New Mexico and Texas.

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

risked estimates. F95 represents a 95-percent chance of at least the amount tabulated; other fractiles are defined similarly. Fractiles are additive under the assumption 

of perfect positive correlation. Shading indicates not applicable]

Total petroleum system 

and assessment units (AUs)

AU

probability

Accumulation 

type

Total undiscovered resources

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

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

Permian Basin Paleozoic Composite Total Petroleum System

Delaware Basin Wolfcamp D Continuous 

Gas AU 1.0 Gas 22,718 72,821 124,966 72,920 850 2,794 5,405 2,917

Delaware Basin Wolfcamp C Continuous 

Gas AU 1.0 Gas 11,757 37,793 67,845 38,510 438 1,455 2,924 1,539

Delaware Basin Wolfcamp C Continuous 

Oil AU 1.0 Oil 382 1,467 3,477 1,635 5,585 21,685 52,927 24,486 404 1,667 4,517 1,961

Delaware Basin Wolfcamp B Lower

Continuous Oil AU 1.0 Oil 2,642 5,297 8,838 5,458 9,519 20,616 38,280 21,815 869 2,011 4,078 2,181

Delaware Basin Wolfcamp B Upper 

Continuous Oil AU 1.0 Oil 4,606 8,861 14,657 9,154 16,524 34,608 63,189 36,601 1,486 3,382 6,799 3,661

Delaware Basin Wolfcamp A Continuous 

Oil AU 1.0 Oil 8,406 12,791 19,556 13,229 14,297 25,219 42,988 26,492 1,259 2,476 4,626 2,648

Third Bone Spring Continuous Oil AU 1.0 Oil 4,941 6,468 9,521 6,739 7,906 12,975 20,851 13,485 501 896 1,551 943

Second Bone Spring Continuous Oil AU 1.0 Oil 3,869 5,096 6,878 5,191 6,201 10,120 15,435 10,370 391 696 1,158 725

First Bone Spring Continuous Oil AU 1.0 Oil 658 2,113 3,588 2,113 2,492 8,119 15,564 8,451 165 555 1,147 592

Lower Avalon Shale Continuous Oil AU 1.0 Oil 507 1,096 1,984 1,153 4,810 10,790 20,864 11,527 440 1,053 2,210 1,151

Upper Avalon Shale Continuous Oil AU 1.0 Oil 718 1,573 2,576 1,599 6,774 15,379 27,165 15,973 614 1,496 2,934 1,599

Total undiscovered continuous resources 26,729 44,762 71,075 46,271 108,583 270,125 490,074 280,630 7,417 18,481 37,349 19,917

ISSN 2327-6916 (print) ISSN 2327-6932 (online) https://doi.org/10.3133/fs20183073