National Assessment of Oil and Gas Fact Sheet

2003 Assessment of Undiscovered Oil and Gas Resources in 

Upper Cretaceous Navarro and Taylor Groups,

Western Gulf Province, Gulf Coast Region, Texas

Application of a 

geology-based 

assessment 

methodology by the 

U.S. Geological Survey 

resulted in estimated 

means of 1,682.8 billion cubic feet of 

undiscovered natural 

gas, 33.2 million barrels of undiscovered 

oil, and 34.3 million 

barrels of undiscovered 

natural gas liquids in 

the Upper Cretaceous 

Navarro and Taylor 

Groups in the Western 

Gulf Province of the 

Gulf Coast Region, 

Texas.

Introduction

The U.S. Geological Survey (USGS) recently completed an assessment of the undiscovered 

oil and gas potential of the Upper Cretaceous Navarro and Taylor Groups in the Western Gulf 

Province of the Gulf Coast Region (fig. 1) as part of a national oil and gas assessment effort.

The assessment of the petroleum potential of the Navarro and Taylor Groups was based on the 

general geologic elements used to define a total petroleum system (TPS)— hydrocarbon source 

rocks (source rock maturation, hydrocarbon generation and migration), reservoir rocks (sequence 

stratigraphy and petrophysical properties), and hydrocarbon traps (trap formation and timing). 

Using this geologic framework, the USGS defined five assessment units (AU) in the Navarro

and Taylor Groups as parts of a single TPS, the Smackover–Austin–Eagle Ford Composite TPS: 

Travis Volcanic Mounds Oil AU, Uvalde Volcanic Mounds Gas and Oil AU, Navarro-Taylor 

Updip Oil and Gas AU, Navarro-Taylor Downdip Gas and Oil AU, and Navarro-Taylor SlopeBasin Gas AU (table 1).

Resource Summary

The USGS assessed undiscovered conventional oil and gas for each of the AUs, resulting 

in estimated means of 1,682.8 billion cubic feet of nonassociated gas and associated gas 

in oil fields, 33.22 million barrels of oil, and 34.26 million barrels of natural gas liquids in 

the Smackover–Austin–Eagle Ford Composite TPS (table 1). All of the undiscovered gas 

is conventional. The Navarro-Taylor Slope-Basin Gas AU contains an estimated mean of 

924.96 billion cubic feet of gas, representing about 55 percent of the total mean undiscovered gas 

resource (1,682.8 billion cubic feet) for the Navarro and Taylor Groups in the province.

Figure 1. Map of the western part 

of the Western Gulf Province 5047 

of the Gulf Coast Region (outlined in 

red), showing geographic distribution 

of assessment units in the Navarro 

and Taylor Groups of the Smackover–

Austin–Eagle Ford Composite Total 

Petroleum System.

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U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet FS-2004-3114

November 2004 Printed on recycled paper

Printed on recycled paper
For Further Information

Geologic studies of total petroleum systems and assessment units and reports on the methodology used in assessing 

resources in the Navarro and Taylor Groups in the Western Gulf Province of the Gulf Coast Region are available at the 

USGS Central Energy Team Web site: http://energy.cr.usgs.gov/oilgas/noga/

Navarro and Taylor Groups Assessment Team

T.S. Dyman (Task Leader: dyman@usgs.gov), S.M. Condon, R.R. Charpentier, T.A. Cook, T.R. Klett, M.D. Lewan, 

M.J. Pawlewicz, R.M. Pollastro, and C.J. Schenk.

Code and

accumulation

type

MAS

Resources

Prob.

(0-1)

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

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

504702 Total: Conventional undiscovered resources in the Smackover–Austin–Eagle Ford Composite Total Petroleum System

Oil Accums. 0.5

1.00

11.21 30.51 64.41 33.22 28.45 90.09 227.55 103.99 0.82 2.69 7.27 3.20

Gas Accums. 3.0 472.79 1,497.75 2,938.92 1,578.81 8.64 28.55 62.04 31.07

Total 1.00 11.21 30.51 64.41 33.22 501.24 1,587.84 3,166.47 1,682.80 9.45 31.25 69.31 34.26

50470201 Travis Volcanic Mounds Oil Assessment Unit

Oil Accums. 0.5

1.00

1.25 2.73 4.81 2.85 0.28 0.66 1.30 0.71 0.01 0.03 0.07 0.04

Gas Accums. 3.0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Total 1.00 1.25 2.73 4.81 2.85 0.28 0.66 1.30 0.71 0.01 0.03 0.07 0.04

50470202 Uvalde Volcanic Mounds Gas and Oil Assessment Unit

Oil Accums. 0.5

1.00

1.27 2.41 3.97 2.48 1.29 2.83 5.20 2.97 0.06 0.14 0.28 0.15

Gas Accums. 3.0 14.33 35.40 61.71 36.38 0.20 0.52 1.00 0.55

Total 1.00 1.27 2.41 3.97 2.48 15.62 38.23 66.91 39.35 0.25 0.65 1.28 0.69

50470203 Navarro-Taylor Updip Oil and Gas Assessment Unit

Oil Accums. 0.5

1.00

6.78 19.41 40.58 21.02 9.43 28.37 64.58 31.58 0.26 0.83 2.02 0.95

Gas Accums. 3.0 60.96 167.86 342.17 180.56 1.01 2.93 6.57 3.25

Total 1.00 6.78 19.41 40.58 21.02 70.38 196.23 406.75 212.14 1.27 3.76 8.60 4.20

50470204 Navarro-Taylor Downdip Gas and Oil Assessment Unit

Oil Accums. 0.5

1.00

1.91 5.95 15.06 6.88 17.44 58.22 156.48 68.72 0.48 1.70 4.90 2.06

Gas Accums. 3.0 158.43 425.92 749.36 436.91 2.95 8.26 16.30 8.76

Total 1.00 1.91 5.95 15.06 6.88 175.88 484.14 905.84 505.63 3.44 9.96 21.20 10.82

50470205 Navarro-Taylor Slope-Basin Gas Assessment Unit

Oil Accums. 0.5

1.00

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Gas Accums. 3.0 239.07 868.58 1,785.68 924.96 4.48 16.84 38.16 18.52

Total 1.00 0.00 0.00 0.00 0.00 239.07 868.58 1,785.68 924.96 4.48 16.84 38.16 18.52

Table 1. Smackover–Austin–Eagle Ford Composite Total Petroleum System, 504702 Assessment Results Summary

[MMBO, million barrels of oil. BCFG, billion cubic feet of gas. MMBNGL, million barrels of natural gas liquids. MAS, minimum accumulation 

size assessed (MMBO or BCFG). Prob., probability (including both geologic and accessibility probabilities) of at least one accumulation equal to or 

greater than the MAS or, for continuous-type resources, at least one additional cell of equal to or greater than the minimum estimated ultimate recovery. 

Accum., accumulation. Results shown are fully risked estimates. For gas accumulations, all liquids are included as natural gas liquids (NGL). 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]