U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2006–3146

February 2007

National Assessment of Oil and Gas Fact Sheet

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

Printed on recycled paper

Introduction

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

assessment of the undiscovered natural gas resources of the Upper 

Cretaceous Tuscaloosa and Woodbine Formations in the downdip 

trend of Louisiana and Texas, which is located in the Western Gulf 

Province of the Gulf Coast region (fig. 1). The downdip trend, as 

defined for this assessment, is bounded on the north by the Lower 

Cretaceous shelf edge, and the southern limit is drawn where 

depths to the top of the two formations are at about 25,000 ft. Laterally, the trend extends along the shelf edge eastward into Federal 

waters of southeast Louisiana and westward to Dewitt County, 

Texas, where it pinches out (fig. 1). The assessment of undiscovered gas resources within the trend 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 and timing). Using this petroleum-system framework, the USGS defined the Upper Cretaceous 

Tuscaloosa-Woodbine TPS and two assessment units (AU): the 

Tuscaloosa Downdip Gas AU and the Woodbine Downdip Gas AU.

Figure 1. Map of the Western Gulf Province of the Gulf Coast region showing distribution of the Tuscaloosa Downdip Gas and 

Woodbine Downdip Gas Assessment Units (AU) in the Upper Cretaceous Tuscaloosa-Woodbine Total Petroleum System.

Using a geology-based assessment 

methodology, the U.S. Geological 

Survey estimated a mean of 20.8 

trillion cubic feet of undiscovered 

natural gas and a mean of 0.60 

billion barrels of undiscovered 

natural gas liquids in the Western 

Gulf Province of the Gulf Coast 

Region, Louisiana and Texas.

0 100 MILES

EXPLANATION

Tuscaloosa Downdip Gas AU (Louisiana)

Woodbine Downdip Gas AU (Texas)

Western Gulf Province

TX

OK AR

MS AL

LA

MEXICO

GULF

OF

MEXICO

Gulf of Mexico

Waco

Dallas

Houston

Jackson

Shreveport

New Orleans

Baton Rouge

35

45

10

55

59

20

49

LOUISIANA

MISSISSIPPI

TEXAS

POLK

COUNTY TYLER

COUNTY

DEWITT

COUNTY

96° 94° 92° 90°

28°

30°

32°
Geologic Model

The downdip Tuscaloosa Formation in Louisiana and the Woodbine Formation in Texas are laterally equivalent units composed of interbedded conglomerate, sandstone, and shale. In Louisiana, coarse clastics form the lower part of the Tuscaloosa, and the upper part is a marine 

shale that correlates with marine shales of the Eagle Ford Group that overlies the Woodbine in Texas. Major production of natural gas in the 

Tuscaloosa and Woodbine Formations is from gas fields localized in two areas: one near Baton Rouge, La. and the other in Polk and Tyler 

Counties, Texas (fig. 1). Large areas extending downdip from the known fields, as well as both east and west of the two producing areas, have 

few well penetrations and are considered to be underexplored.

In the Upper Cretaceous Tuscaloosa-Woodbine TPS, gas is produced from overpressured sandstone reservoirs that were deposited 

in deltas and prograding shelf-margin complexes basinward (southward) of the Lower Cretaceous shelf edge. Jurassic Louann Salt underlies a thick Lower Cretaceous carbonate section that is subjacent to the Tuscaloosa and Woodbine, and deformation of the salt into ridges 

and diapirs influenced where sediment accumulated in the trend. In areas of salt withdrawal between ridges, greater sediment deposition 

led to syndepositional growth faulting and the formation of rollover anticlines. The major traps that have been explored are growth faults 

associated with these anticlines and diapirs. In producing areas, the bulk of the gas in Tuscaloosa and Woodbine reservoirs formed in 

shales within these formations, and the gas migrated vertically into sandstone reservoirs where it accumulated adjacent to sealing (lowpermeability) shales and growth faults. Geologic and petroleum-system models indicate that the controls on sediment deposition and on gas 

generation, migration, and accumulation may be similar in underexplored areas of the downdip trend. Thus large volumes of gas likely are 

present downdip as well as along strike of known producing areas, assuming the presence of adequate reservoirs, seals, and traps.

Resource Summary

The USGS assessed undiscovered conventional gas resources 

in the Tuscaloosa Downdip Gas and Woodbine Downdip Gas 

AUs, exclusive of reserve growth, resulting in combined mean 

estimates of 20.8 trillion cubic feet of non-associated gas (TCFG) 

and 0.60 billion barrels of natural gas liquids (table 1). The Tuscaloosa Downdip Gas AU contains approximately 16.2 TCFG, 

representing about 78 percent of the total mean undiscovered 

nonassociated gas resource. The remaining 4.6 TCFG is in the 

Woodbine Downdip Gas AU. The assessment was based on 2000 

IHS well and production data (IHS Energy Group, 2001a, b) and 

1998 Nehring field data (NRG Associates, 2000). A reevaluation 

using 2003 IHS (IHS Energy Group, 2004a, b) and 2003 Nehring 

(NRG Associates, 2005) data indicates that 53 wells were drilled 

since 2000 and no new fields have been discovered since 1998; 

thus there is no change in the assessed resources of the trend.

References

IHS Energy Group, 2001a, PI/Dwights PLUS U.S. production data: 

Englewood, Colo., IHS Energy Group; database available from 

IHS Energy Group, 15 Inverness Way East, D205, Englewood, 

CO 80112, U.S.A.

IHS Energy Group, 2001b, PI/Dwights PLUS U.S. well data: 

Englewood, Colo., IHS Energy Group; database available from 

IHS Energy Group, 15 Inverness Way East, D205, Englewood, 

CO 80112, U.S.A.

IHS Energy Group, 2004a, PI/Dwights PLUS U.S. production data: 

Englewood, Colo., IHS Energy Group; database available from 

IHS Energy Group, 15 Inverness Way East, D205, Englewood, 

CO 80112, U.S.A.

IHS Energy Group, 2004b, PI/Dwights PLUS U.S. well data: Englewood, Colo., IHS Energy Group; database available from IHS 

Energy Group, 15 Inverness Way East, D205, Englewood, CO 

80112, U.S.A.

NRG Associates, 2000, The significant oil and gas fields of the 

United States: Colorado Springs, Colo., NRG Associates, Inc.; 

database available from NRG Associates, Inc., P.O. Box 1955, 

Colorado Springs, CO 80901, U.S.A.

NRG Associates, 2005, The significant oil and gas fields of the 

United States: Colorado Springs, Colo., NRG Associates, Inc.; 

database available from NRG Associates, Inc., P.O. Box 1955, 

Colorado Springs, CO 80901, U.S.A.

For Further Information

Reports on geologic studies of the total petroleum system 

and assessment unit and the methodology used in the TuscaloosaWoodbine assessment are in progress. Assessment results are available at the USGS Central Energy Team website: http://energy.cr.usgs.

gov/oilgas/noga/

Assessment Team

Janet K. Pitman (Task Leader; jpitman@usgs.gov), Russell F. 

Dubiel, Philip H. Nelson, Joyce Kibler, Ronald R. Charpentier, Troy A. 

Cook, Timothy R. Klett, Richard Pollastro, and Christopher J. Schenk.

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

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

Gas 8,117 15,405 26,659 16,164 197 407 776 437

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

Gas 1,640 4,261 8,771 4,622 54 149 336 166

0 0 0 0 9,757 19,666 35,431 20,786 251 556 1,112 603

Total Conventional

Resources

Upper Cretaceous TuscaloosaWoodbine TPS

Total undiscovered resources

Gas (BCFG)

Tuscaloosa Downdip Gas AU

Woodbine Downdip Gas AU

NGL (MMBNGL) Field

type

Total Petroleum System

(TPS)

and Assessment Units (AU)

Oil (MMBO)

Conventional Oil 

and Gas Resources

Table 1. Upper Cretaceous Tuscaloosa-Woodbine Total Petroleum System assessment results.

[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 fields, all

liquids are included under the NGL (natural gas liquids) category. F95 denotes a 95-percent chance of at least the amount tabulated. Other fractiles are defined similarly.

Fractiles are additive, assuming perfect positive correlation. Totals reflect rounding to nearest whole number. Gray shading indicates not applicable]