National and Global Petroleum Assessment

Assessment of Tight-Gas Resources in Canyon Sandstones 

of the Val Verde Basin, Texas, 2016

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2016–3039

July 2016 Printed on recycled paper

Using a geology-based assessment methodology, the U.S. Geological Survey assessed mean resources of 5 trillion cubic feet of gas 

and 187 million barrels of natural gas liquids in tight-gas assessment units in the Canyon sandstones of the Val Verde Basin, Texas.

Canyon sandstone was not assessed in this 

study. The sandstones represent multiple 

phases of deposition in prograding slope 

channel and basin-floor submarine fan 

systems with varying directions of provenance. For example, the Ozona sandstones 

were sourced from the southwest, whereas 

the Sonora sandstones were sourced from 

the northeast (Hamlin, 2009). Maps of 

sandstone thicknesses (Hamlin and others, 

1995; Hamlin, 2009) and production data 

guided the geologic definition of the assessment units in this study.

Four assessment units (AU) were 

defined and assessed in the Ozona and 

Sonora sandstones of the Val Verde 

Basin. The four assessment units are 

contained within the Permian Basin 

Paleozoic Composite Total Petroleum 

System (TPS). Given that approximately 

15,000 wells have been drilled and tested 

in the Canyon sandstone, production 

“fairways” have come into focus through 

time that are defined by thicker sandstone 

intervals and thus denser drilling and production. These fairways were also used as 

a basis for AU definition. The production 

fairway in the Ozona sandstone is defined 

as the Ozona Sandstone Fairway Tight 

Gas AU (fig. 1), and the area surrounding the fairway is the Ozona Sandstone 

Peripheral Tight Gas AU. Likewise, 

the production fairway in the Sonora 

sandstone defined the Sonora Sandstone 

Fairway Tight Gas AU, and the surrounding area is the Sonora Sandstone 

Peripheral Tight Gas AU. The outlines of 

the peripheral AUs generally follow the 

Ozona and Sonora sandstone boundaries 

developed by Hamlin and others (1995). 

Assessment input data for the four AUs 

are summarized in table 1.

Introduction

The U.S. Geological Survey (USGS) 

recently completed a geology-based assessment of technically recoverable tight-gas 

resources in the Canyon sandstones of the 

Val Verde Basin in southwest Texas (fig. 1). 

The Val Verde Basin is the foredeep to the 

late Paleozoic, north-verging OuachitaMarathon fold and thrust belt. “Canyon 

sandstones” is a collective term for several 

sandstone intervals deposited in deep-water 

environments in the developing foredeep 

during the Late Pennsylvanian (Missourian 

to Virgilian?) and Early Permian 

(Wolfcampian) (Bebout and Garrett, 1989; 

Hamlin and others, 1995; Hamlin, 2009). 

Canyon sandstones include the lower 

Canyon sandstone, Sonora sandstone, and 

Ozona sandstone intervals (Hamlin and 

others, 1995; Hamlin, 2009). The lower 

Figure 1. Map of the Val Verde Basin, Texas. Assessment unit (AU) boundaries approximate facies maps of the various Canyon sandstones.

VAL VERDE

CROCKETT

TERRELL

EDWARDS REAL

SUTTON

Real

KIMBLE

KINNEY UVALDE

SCHLEICHER PECOS MENARD

KERR

102° 101° 100°

30°

T E X A S

UNITED STATES

MEXICO

Source: National Park Service

0 20 KILOMETERS 10

0 10 20 MILES

TEXAS

MEXICO

OKLAHOMA

NEW 

MEXICO

GULF

of

MEXICO

Area of study

Val Verde Basin

Ozona Sandstone Fairway 

 Tight Gas AU

EXPLANATION

Sonora Sandstone Fairway

 Tight Gas AU

Ozona Sandstone Peripheral 

 Tight Gas AU

Sonora Sandstone Peripheral

 Tight Gas AU

Val Verde Basin (part)
ISSN 2327-6916 (print) ISSN 2327-6932 (online) http://dx.doi.org/10.3133/fs20163039

Tight-Gas Resource Summary

The USGS assessed technically recoverable tight-gas resources in four continuous AUs in Canyon sandstones (table 2). Assessed 

mean resources are 5,004 billion cubic feet of tight gas and 187 million barrels of natural gas liquids. For the Ozona Sandstone Fairway 

Tight Gas AU, the assessed mean resource is 1,615 billion cubic feet of gas (BCFG), with an F95–F5 range from 730 to 2,683 BCFG. The 

assessed mean resource for the Ozona Sandstone Peripheral Tight Gas AU is 222 BCFG, with an F95–F5 range from 68 to 425 BCFG. 

For the Sonora Sandstone Fairway Tight Gas AU, the assessed mean resource is 2,779 BCFG, with an F95–F5 range from 1,223 to 

4,677 BCFG. The assessed mean resource for the Sonora Sandstone Peripheral Tight Gas AU is 388 BCFG, with an F95–F5 range from 

117 to 735 BCFG. For the four tight-gas AUs, the assessed mean resource for natural gas liquids is 187 million barrels of natural gas 

liquids (MMBNGL), with an F95–F5 range from 74 to 338 MMBNGL. More than half (56 percent or 2,779 BCFG) of the total assessed 

mean tight-gas resource is in the Sonora Sandstone Fairway Tight Gas AU.

Assessment input data

Ozona Sandstone Fairway Tight Gas AU Ozona Sandstone Peripheral Tight Gas AU

Minimum Mode Maximum Calculated

mean Minimum Mode Maximum Calculatedmean

Potential production area of AU (acres) 40,000 180,000 270,000 163,333 10,000 400,000 586,000 332,000

Average drainage area of wells (acres) 10 20 30 20 40 80 120 80

Percentage of area untested in AU 50 60 70 60 64 76 88 76

Success ratios (%) 85 90 95 90 50 60 70 60

Average EUR (BCFG) 0.3 0.35 0.4 0.352 0.08 0.1 0.4 0.116

AU probability 1.0 1.0

Assessment input data

Sonora Sandstone Fairway Tight Gas AU Sonora Sandstone Peripheral Tight Gas AU

Minimum Mode Maximum Calculated

mean Minimum Mode Maximum Calculatedmean

Potential production area of AU (acres) 60,000 287,000 431,000 259,333 10,000 900,000 1,197,000 702,333

Average drainage area of wells (acres) 10 20 30 20 40 80 120 80

Percentage of area untested in AU 50 65 80 65 68 72 86 75

Success ratios (%) 85 90 95 95 40 50 60 50

Average EUR (BCFG) 0.3 0.35 0.4 0.352 0.08 0.1 0.4 0.116

AU probability 1.0 1.0

Table 1. Key assessment input data for the four continuous assessment units in the Canyon sandstones of the Val Verde Basin, Texas.

[AU, assessment unit; %, percent; EUR, estimated ultimate recovery per well; BCFG, billion cubic feet of gas. The EUR, well drainage area, and success ratios are 

taken from U.S. shale-gas analogs. The average EUR input is the minimum, median, and calculated mean. Shading indicates not applicable]

Total petroleum system (TPS) 

and assessment unit (AU)

AU 

probability

Accumulation 

type

Total undiscovered resources

Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean

Permian Basin Paleozoic Composite TPS

Ozona Sandstone Fairway Tight Gas AU 1.0 Gas 730 1,562 2,683 1,615 8 18 35 19

Ozona Sandstone Peripheral Tight Gas AU 1.0 Gas 68 208 425 222 4 12 27 13

Sonora Sandstone Fairway Tight Gas AU 1.0 Gas 1,223 2,681 4,677 2,779 58 131 245 139

Sonora Sandstone Peripheral Tight Gas AU 1.0 Gas 117 365 735 388 4 14 31 16

Total undiscovered unconventional resources 2,138 4,816 8,520 5,004 74 175 338 187

Table 2. Assessment results for the four continuous assessment units in the Canyon sandstones of the Val Verde Basin, Texas.

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

all liquids are included under the NGL category. 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]

References Cited

Bebout, D.G., and Garrett, Jr., C.M., 1989, PN–5: Upper Pennsylvanian and 

Lower Permian slope and basinal sandstone, in Kosters, E.C., Bebout, D.G., 

Seni, S.J., Garrett, Jr., C.M., Brown, Jr., L.F., Hamlin, H.S., Dutton, S.P., 

Ruppel, S.C., Finley, R.J., and Tyler, Noel, Atlas of major Texas gas reservoirs: Austin, Texas, Bureau of Economic Geology, p. 116–118.

Hamlin, H.S., 2009, Ozona sandstone, Val Verde Basin, Texas—Synorogenic 

stratigraphy and depositional history in a Permian foredeep basin: American 

Association of Petroleum Geologists Bulletin, v. 93, no. 5, p. 573–594.

Hamlin, H.S., Clift, S.J., Dutton, S.P., Hentz, T.F., and Laubach, S.E., 1995, 

Canyon sandstones—A geologically complex natural gas play in slope and 

basin facies, Val Verde Basin, southwest Texas: Bureau of Economic Geology, 

University of Texas at Austin, Report of Investigations no. 232, 74 p.

Canyon Sandstones Assessment Team

Christopher J. Schenk, Marilyn E. 

Tennyson, Timothy R. Klett, Tracey J. Mercier, 

Michael E. Brownfield, Stephanie B. Gaswirth, 

Sarah J. Hawkins, Heidi M. Leathers-Miller, 

Kristen R. Marra, Thomas M. Finn, and 

Janet K. Pitman

For More Information

Assessment results are available at the 

USGS Energy Resources Program Web site at 

http://energy.usgs.gov.