U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2012–3003

February 2012 Printed on recycled paper

National Assessment of Oil and Gas

Assessment of Undiscovered Oil and Gas Resources in 

Conventional and Continuous Petroleum Systems in the Upper 

Cretaceous Eagle Ford Group, U.S. Gulf Coast Region, 2011

Introduction

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

a geology-based assessment of the undiscovered, technically 

recoverable oil and gas resources in Upper Cretaceous strata 

of the U.S. Gulf Coast region, which includes parts of Texas, 

Louisiana, Arkansas, Mississippi, Alabama, and Florida (fig. 1). 

The assessed Upper Cretaceous strata in this report includes the 

Eagle Ford Group, which is interbedded with laterally equivalent sandstones of the Woodbine and Tuscaloosa Formations; 

other lateral equivalents are the Eagle Ford Shale, and, in part, 

the Tuscaloosa marine shale. Nomenclature is a combination of 

formal and informal groups, and formation and member names 

that reflect the common designation and usage in the region by 

State, industry, U.S. Geological Survey, and academic geologists. The assessment was based on the geologic elements and 

petroleum processes used to define a total petroleum system 

(TPS), which includes petroleum source rocks (source-rock 

maturation and petroleum generation and migration), reservoir 

and seal rocks (sequence stratigraphy and petrophysical properties), and petroleum traps (trap formation, timing, and seals). 

Using this petroleum-system framework, the USGS defined 

Using a geology-based assessment methodology, the U.S. Geological Survey assessed means of (1) 141 million barrels of oil 

(MMBO), 502 billion cubic feet of natural gas (BCFG), and 16 million barrels of natural gas liquids (MMBNGL) in the conventional Eagle Ford Updip Sandstone Oil and Gas Assessment Unit (AU); (2) 853 MMBO, 1,707 BCFG, and 34 MMBNGL in 

the continuous Eagle Ford Shale Oil AU; and (3) 50,219 BCFG and 2,009 MMBNGL in the continuous Eagle Ford Shale Gas 

AU in onshore lands and State waters of the Gulf Coast.

Figure 1. Map of the Gulf Coast region showing part of the Upper Jurassic–Cretaceous–Tertiary Composite Total Petroleum System 

(red line), assessment unit (AU) boundaries (blue, light blue, and orange lines), and the Lower Cretaceous shelf edge (brown line). Lower 

Cretaceous shelf edge after Martin (1980) and Ewing and Lopez (1991). 

0 100

100

200 MILES 

0 200 KILOMETERS

24°

26°

28°

30°

32°

34°

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38°

 104° 102° 100° 98° 96° 94° 92° 90° 88° 86° 84° 82° 80° 78°

TEXAS

FLORIDA

GEORGIA

OKLAHOMA

KANSAS

ALABAMA

LOUISIANA

SOUTH CAROLINA

COLORADO

MISSISSIPPI

ARKANSAS

MISSOURI

ILLINOIS INDIANA

TENNESSEE

KENTUCKY

NORTH CAROLINA

VIRGINIA

WEST

VIRGINIA

UNITED STATES

MEXICO

GULF OF MEXICO

ATLANTIC

OCEAN

Lower Cretaceous shelf edge

Upper Jurassic–Cretaceous–Tertiary

 Composite Total Petroleum System

Eagle Ford Updip Sandstone Oil and

 Gas Assessment Unit (AU)

Eagle Ford Shale Oil AU

Eagle Ford Shale Gas AU

EXPLANATION
three assessment units (AUs) for these Cenomanian−Turonian 

rocks: (1) the Eagle Ford Updip Sandstone Oil and Gas AU, 

(2) the Eagle Ford Shale Oil AU, and (3) the Eagle Ford Shale 

Gas AU (fig. 1).

Geologic Summary

The USGS defined the Upper Jurassic−Cretaceous−

Tertiary Composite TPS and three assessment units (AUs) with 

technically recoverable undiscovered conventional and continuous oil and gas resources in Upper Cretaceous strata (fig. 1). 

The assessed conventional oil and gas undiscovered resources 

are in sandstone reservoirs in the Tuscaloosa and Woodbine 

Formations in Louisiana and Texas, respectively, whereas the 

continuous oil and continuous gas resources reside in the Eagle 

Ford Shale in Texas and the Tuscaloosa marine shale in Louisiana. Conventional resources in the Tuscaloosa and Woodbine 

are included in the Eagle Ford Updip Sandstone Oil and Gas 

AU, which encompasses an area where the Eagle Ford Shale 

and Tuscaloosa marine shale display vitrinite reflectance (Ro) 

values <0.6 percent. The conventional gas resources in the socalled “downdip” Tuscaloosa and Woodbine shelf-margin deltas 

previously were assessed and published in 2007 (Pitman and 

others, 2007). The continuous Eagle Ford Shale Oil AU lies 

beneath part of the conventional Eagle Ford Updip Sandstone 

Oil and Gas AU, immediately updip of the Lower Cretaceous 

shelf edge, and is defined by thermal maturity values within the 

Eagle Ford Shale and the Tuscaloosa marine shale that range 

from 0.6 to 1.2 percent Ro. Similarly, the continuous Eagle 

Ford Shale Gas AU is defined primarily downdip of the shelf 

edge where the source rocks have Ro values greater than 1.2 

percent.

Resource Summary

The USGS assessed undiscovered, technically recoverable 

oil and gas resources in the three assessment units (table 1). The 

assessed means are (1) 141 million barrels of oil (MMBO), 502 

billion cubic feet of natural gas (BCFG), and 16 million barrels 

of natural gas liquids (MMBNGL) in the conventional Eagle 

Ford Updip Sandstone Oil and Gas AU; (2) 853 MMBO, 1,707 

BCFG, and 34 MMBNGL in the continuous Eagle Ford Shale 

Oil AU; and (3) 50,219 BCFG and 2,009 MMBNGL in the 

continuous Eagle Ford Shale Gas AU.

For Further Information

Supporting geologic studies and the methodology used in 

the 2010 Jurassic and Cretaceous Gulf Coast Assessment are in 

progress. Assessment results are available at the USGS Central 

Energy Resources Science Center website: http://energy.cr.usgs.

gov/oilgas/noga.

References Cited

Martin, R.G., 1980, Distribution of salt structures, Gulf of Mexico: 

U.S. Geological Survey Miscellaneous Field Studies Map MF-1213, 

scale 1:2,500,000.

Ewing, T.E., and Lopez, R.F., 1991, Principal structural features, in

Salvador, A., ed., The Gulf of Mexico Basin: The Geological Society of America, The Geology of North America, v. J, plate 2.

Pitman, J.K., Dubiel, R.F., Nelson, P.H., Kibler, Joyce, Charpentier, 

R.R., Cook, T.A., Klett, T.R., Pollastro, Richard, and Schenk, C.J., 

2007, Assessment of undiscovered gas resources in the Upper 

Cretaceous Tuscaloosa and Woodbine Formations, Western Gulf 

Province of the Gulf Coast region, Louisiana and Texas, 2007: U.S. 

Geological Survey Fact Sheet 2006−3146.

Assessment Team

Russell F. Dubiel (rdubiel@usgs.gov), Janet K. Pitman, Ofori 

N. Pearson, Krystal Pearson, Scott A. Kinney, Michael D. 

Lewan, Lauri Burke, Laura R.H. Biewick, Ronald R. Charpentier, Troy A. Cook, Timothy R. Klett, Richard M. Pollastro, and 

Christopher J. Schenk.

Total Petroleum Systems 

(TPS) 

and Assessment Units (AU)

Field

type 

Total undiscovered resources

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

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

Upper Jurassic–Cretaceous–Tertiary Composite TPS (504901)

Eagle Ford Updip Sandstone Oil 

and Gas AU (50490128)

Oil 41 136 253 141 53 184 381 197 1 4 8 4

Gas 86 289 571 305 3 11 24 12

Total conventional

 resources 41 136 253 141 139 473 952 502 4 15 32 16

Eagle Ford Shale Oil AU 

(50490170) Oil 341 758 1,687 853 625 1,486 3,533 1,707 12 29 74 34

Eagle Ford Shale Gas AU 

(50490167) Gas 23,470 46,150 90,747 50,219 851 1,809 3,842 2,009

Total continuous

 resources 341 758 1,687 853 24,095 47,636 94,280 51,926 863 1,838 3,916 2,043

Total undiscovered

oil and gas resources 382 894 1,940 994 24,234 48,109 95,232 52,428 867 1,853 3,948 2,059

[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. Fractiles are additive under the 

assumption of perfect positive correlation. TPS, total petroleum system; AU, assessment unit. Gray shading indicates not applicable]

Table 1. Eagle Ford assessment results.