U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2010–3043

June 2010

Assessment of Undiscovered Natural Gas Resources of the 

Arkoma Basin Province and Geologically Related Areas

Printed on recycled paper

Introduction

The U.S. Geological Survey (USGS) in 2010 completed 

an assessment of the undiscovered, technically recoverable 

petroleum resources of the Arkoma Basin Province, which 

includes the Arkoma Basin and Ouachita Thrust Belt, and two 

adjacent areas. The principle focus of this assessment is the 

Arkoma Basin of central Arkansas and east-central Oklahoma 

Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean volumes of 38 trillion cubic feet (TCF) of undiscovered natural gas, 159 million barrels of natural gas liquid (MMBNGL), and no oil in accumulations of 0.5 million barrels (MMBO) or larger in 

the Arkoma Basin Province and related areas. More than 97 percent of the undiscovered gas occurs in continuous accumulations — 70 percent in 

shale gas formations, 18 percent in a basin-centered accumulation with tight sandstone reservoirs, and 9 percent in coal beds. Less than 3 percent 

of the natural gas occurs in conventional accumulations.

and the Ouachita Thrust Belt of southeast Oklahoma, southcentral Arkansas, and west-central Mississippi (fig. 1). Other 

areas assessed include (1) the Post-Ouachita Successor Basin 

of northeast Texas, south Arkansas, and north and northwest 

Louisiana; and (2) part of the Reelfoot Rift in northeast Arkansas and southeast Missouri (fig. 1).

ARKANSAS

LOUISIANA

MISSISSIPPI

OKLAHOMA

TENNESSEE

TEXAS

MISSOURI

96°W 95°W 94°W 93°W 92°W 91°W 90°W 89°W

36°N

35°N

34°N

33°N

32°N

31°N

Cretaceous Overlap

Tulsa

Memphis

Dallas

Jackson

Shreveport

Little Rock

0 50 100 MILES

0 50 100 KILOMETERS

MAP LOCATION

Arkoma Basin

Ouachita Thrust Belt

Reelfoot Rift

Assessment Units

Arkoma Coalbed Gas

Arkoma Shelf

Arkoma Shale Gas (subdivided; fig. 2)

Arkoma Deep Basin Conventional

Arkoma-Ouachita Foredeep Continuous 

Ouachita Thrust Belt

Post-Ouachita Successor Basin

Elvins Shale Gas

Figure 2

EXPLANATION

Figure 1. Arkoma Basin Province showing assessment unit (AU) boundaries as well as generalized areas of Arkoma Basin, 

Ouachita Thrust Belt, and Reelfoot Rift. The area identified as “Arkoma Shale Gas” includes six AUs, which are delineated in 

figure 2. Note that the Arkoma Deep Basin Conventional and Arkoma-Ouachita Foredeep Continuous AUs share a common 

boundary but are separated stratigraphically (vertically). Black dashed rectangle is area shown in figure 2.

National Oil and Gas Assessment Project
The USGS assessment is based on geologic elements of 

a total petroleum system (TPS) that include (1) source-rock 

distribution, thickness, organic richness, thermal maturation, 

and petroleum generation and migration; (2) reservoir-rock 

type (conventional or continuous), distribution, and quality; 

and (3) character of traps and time of trap formation relative 

to petroleum generation and migration. Consideration of these 

TPS elements within a context of the reconstructed geologic 

history of each area, combined with analysis of historical 

petroleum exploration and production data, was used to estimate 

undiscovered, technically recoverable petroleum resources. 

This approach resulted in the definition of 5 TPSs containing 13 assessment units (AU, fig. 1). Undiscovered petroleum 

resources were estimated quantitatively for 10 of the AUs; 

no quantitative assessment was conducted for 3 of the AUs 

(table 1).

Total Undiscovered Resources

Gas (BCFG) NGL (MMBNGL)

Total Petroleum System (TPS) and 

Assessment Unit (AU)

Field 

Type

F95 F50 F5 Mean F95 F50 F5 Mean

Woodford - Chattanooga TPS

Woodford Shale Gas AU Gas 6,065 10,165 17,036 10,678 34 111 356 142

Chattanooga Shale Gas AU Gas 800 1,502 2,821 1,617 0 0 0 0

Fayetteville - Caney TPS

Fayetteville Shale Gas - Mississippi 

Embayment AU Not assessed quantitatively

Fayetteville Shale Gas - High GammaRay Depocenter AU

Gas 6,202 8,859 12,656 9,070 0 0 0 0

Fayetteville Shale Gas - Western 

Arkansas Basin Margin AU

Gas 2,260 3,939 6,865 4,170 0 0 0 0

Caney Shale Gas AU Gas 566 1,056 1,971 1,135 2 6 19 8

Elvins Shale TPS

Elvins Shale Gas AU Not assessed quantitatively

Arkoma - Ouachita Paleozoic 

Composite TPS

Arkoma - Ouachita Foredeep 

Continuous AU

Gas 3,189 6,246 12,233 6,790 0 0 0 0

Arkoma Coalbed Gas TPS

Arkoma Coalbed Gas AU CBG 2,197 3,391 5,234 3,511 0 0 0 0

Total Continuous Resources 36,971 150

Arkoma - Ouachita Paleozoic 

Composite TPS

Arkoma Shelf AU Gas 17 43 80 45 0 1 2 1

Arkoma Deep Basin Conventional AU Gas 46 213 589 252 0 0 0 0

Ouachita Thrust Belt AU Gas 104 659 1,720 753 1 6 18 8

Post-Ouachita Successor Basin AU Not assessed quantitatively

Total Conventional Resources 1,050 9

Total Undiscovered Gas Resources 38,021 159

Continuous Gas Resources Conventional Gas

Resources Continuous Gas Resources

Table 1. Arkoma Basin Province assessment results, including estimated volumes of undiscovered, technically recoverable gas and 

natural gas liquids. Oil results are not shown because all estimated values in accumulations of 0.5 MMBO and larger are zero.

[BCFG, billion cubic feet of gas; NGL, natural gas liquids; MMBNGL, million barrels of natural gas liquids; TPS, total petroleum system; AU, assessment unit. 

Results shown are fully risked estimates. F95 represents a 95 percent chance of at least the amount tabulated; other fractiles are defined similarly]

Resource Summary

The USGS estimated mean values of 38,021 billion cubic 

feet of gas (BCFG) and 159 million barrels of natural gas 

liquids (MMBNGL) for undiscovered continuous and conventional resources in the Arkoma Basin and Ouachita Thrust Belt 

(table 1). No oil was estimated to occur in accumulations of 0.5 

million barrels (MMBO) or larger.

More than 26 trillion cubic feet of gas (TCFG), 70 percent 

of the total undiscovered gas, occurs in shale-gas AUs defined 

within two formations. The Devonian-Mississippian Woodford 

Shale, from which more than 700 BCFG has been produced, 

is estimated to contain 10.7 TCFG in Oklahoma and western 

Arkansas (fig. 2A). The laterally equivalent Chattanooga Shale, 

which has not been a focus of historical exploration activity, 

is estimated to contain 1.6 TCFG in Arkansas (fig. 2A). The 

younger, Mississippian Fayetteville Shale, from which more 

than 700 BCFG has been produced, is estimated to contain 
13.2 TCFG in two AUs in Arkansas (fig. 2B). The laterally 

equivalent Caney Shale, which has been a minor focus of 

historical exploration activity, is estimated to contain 1.1 TCFG 

in Oklahoma (fig. 2B).

The deep basin that straddles the boundary between the 

Arkoma Basin and the Ouachita Thrust Belt (fig. 1) has been 

interpreted to hold a basin-centered, continuous gas accumulation with tight-sandstone reservoirs of Pennsylvanian age. This 

Arkoma-Ouachita Foredeep Continuous AU is estimated to 

contain 6.8 TCFG, 18 percent of the total undiscovered gas. The 

Arkoma Coalbed Gas AU is estimated to contain 3.5 TCFG, 

9 percent of the total undiscovered gas, in coals of 

Pennsylvanian age.

Conventional gas resources were assessed in three AUs 

containing reservoirs that range from Cambrian to Pennsylvanian age. The Arkoma Shelf, Arkoma Deep Basin Conventional, 

and Ouachita Thrust Belt AUs are estimated to contain 45 

BCFG, 252 BCFG, and 753 BCFG, respectively (table 1). The 

96°W 95°W 94°W 93°W 92°W 91°W

36°N

35°N

36°N

35°N

Caney Shale Gas

Fayetteville 

Shale Gas - 

High 

Gamma-Ray 

Fayetteville

Shale Gas -

Mississippi

Embayment

Fayetteville Shale

Gas - Western

Arkansas Basin

Margin

Woodford Shale Gas

Cretaceous Overlap

Cretaceous Overlap

ARKANSAS

OKLAHOMA

ARKANSAS

OKLAHOMA

Tulsa

Little Rock

Tulsa

Little Rock

0 50 100 MILES

0 50 100 KILOMETERS

A

B

Chattanooga Shale Gas

Figure 2. Specific boundaries for Arkoma Shale Gas assessment units (AU). (A) Two AUs in 

the Woodford and Chattanooga Shales, defined based on maps of high gamma-ray response 

in wireline logs. (B) Four AUs in the Fayetteville and Caney Shales, defined based on maps of 

high gamma-ray response in wireline logs and of thermal maturity. Results for all these AUs are 

shown in table 1. Area of map shown by dashed, black rectangle in figure 1.

sum of 1 TCFG for these three AUs represents 3 percent of the 

total undiscovered gas.

Natural gas liquids were assessed in two shale-gas and two 

conventional AUs (table 1) and their presence is limited to the 

westernmost parts of the Arkoma Basin and Ouachita Thrust 

Belt, areas characterized by low thermal maturity (<1 percent 

vitrinite reflectance).

Three additional assessment units were defined 

and analyzed but not assessed quantitatively. These include 

the (1) Fayetteville Shale Gas – Mississippi Embayment AU 

(fig. 2B), (2) Elvins Shale Gas AU (Cambrian shale in the 

Reelfoot Rift, fig. 1), and (3) Post-Ouachita Successor Basin 

AU (Pennsylvanian-Permian strata; fig. 1). Each of these areas 

has been tested by a small number of exploration wells, some of 

which have yielded shows of petroleum but none of which has 

sustained production. These exploration histories, together with 

a paucity of geologic data to constrain a detailed analysis, led to 

the conclusion that insufficient information exists to warrant a 

quantitative assessment (table 1).
For Further Information

Supporting geologic reports on the Arkoma 

Basin assessment are in preparation. These reports 

will be available as completed at the USGS Web site 

at: http://energy.cr.usgs.gov/oilgas/noga

Arkoma Basin Province Assessment Team:

David W. Houseknecht (Task Leader; dhouse@

usgs.gov), James L. Coleman, Robert C. Milici, 

Christopher P. Garrity, William A. Rouse, Bryant 

R. Fulk, Stanley T. Paxton, Marvin M. Abbott, John 

C. Mars, Troy A. Cook, Christopher J. Schenk, 

Ronald R. Charpentier, Timothy R. Klett, Richard M. 

Pollastro, and Geoffrey S. Ellis.

Photograph above: Exposure near Marshall, Arkansas of interfingering contact between the dark gray Fayetteville Shale and the overlying, buff 

colored Pitkin Limestone, both of Mississippian age. Elsewhere in the Arkoma Basin, the Fayetteville Shale is both the source and reservoir for a 

large continuous gas accumulation and the Pitkin Limestone locally is a reservoir for conventional gas accumulations. White object at lower-left is 

1 foot long. Photograph by Stanley T. Paxton, U.S. Geological Survey.

Photograph above: Exposure of the Devonian-Mississippian Arkansas Novaculite near 

Atoka, Oklahoma. The formation consists of thin interbeds of chert (blocky, resistant beds) 

and black, organic shale (recessive beds) and at this exposure is folded and faulted. The 

Arkansas Novaculite is a potential source and reservoir for conventional gas accumulations 

in the Ouachita Thrust Belt. Hammer with 1 foot handle near center of photograph for scale. 

Photograph by David W. Houseknecht, U.S. Geological Survey

Photograph left: Exposure of the Pennsylvanian 

Atoka Formation near Blue Mountain, Arkansas. 

The dark-colored mudstone on the left was 

deposited on a marine slope and deformed by 

gravity slumping. The light-colored sandstone on 

the right was deposited by turbidity currents that 

incised an erosional channel into the underlying 

mudstone. Sandstone such as this constitutes the 

main reservoirs in the Arkoma-Ouachita foredeep 

continuous gas accumulation. Geologist for 

scale. Photograph by David W. Houseknecht, U.S. 

Geological Survey.