U.S. Department of the Interior

U.S. Geological Survey

Circular 1386

Version 1.1, September 2013

National Assessment of Geologic Carbon Dioxide Storage 

Resources—Results

120°W 110°W 100°W 90°W 80°W 70°W

40°N

30°N

160°W 140°W

65°N

60°N

55°N

180°W

Evaluated area

Assessed area

EXPLANATION 0 250 500 750 1,000KILOMETERS

0 250 500 MILES 0 250 500 KILOMETERS

0 250 MILES

Pacific

Northwest

Rocky Mountains

and Northern

Great Plains

Western

Mid-Continent Eastern Mesozoic Rift Basins

Eastern Mid-Continent

Coastal Plains

Alaska

California

Bighorn Basin

Powder

River

Basin

Wind River Basin

Greater Green

River Basin

Hanna, 

Laramie, and 

Shirley Basins

Western

Oregon and Washington

Basins

Columbia Basin of 

Oregon, Washington, 

and Idaho

Wyoming–Idaho–Utah 

Thrust Belt

Alaska 

North Slope

Kandik 

Basin

U.S. Gulf Coast Bend Arch

and Fort

Worth Basin

Arkoma Basin

Denver 

Basin

Anadarko and Southern 

Oklahoma Basins

Eastern 

Great 

Basin

Sacramento

Basin

San 

Joaquin 

Central Basin California 

Coast Basins

Ventura 

Basin

Los Angeles 

Basin

Uinta and Piceance Basins

Paradox 

Basin

San Juan

Basin

Raton 

Basin

Williston 

Basin

Illinois 

Basin

Michigan 

Basin

South Florida 

Basin

Black 

Warrior 

Basin

Appalachian 

Basin

Kansas 

Basins

Palo Duro 

Basin

Permian Basin

Eastern 

Mesozoic 

Rift Basins

Atlantic 

Coastal Plain

Base map from Jarvis

and others (2008)

CGIAR-Consortium

for Spatial Information

SRTM 90m Database
Cover. Map of the conterminous United States and Alaska showing 8 regions (separated by bold 

dashed lines and labeled in a bold font), evaluated areas (bluish gray) that were not assessed, and 

36 areas (pattern) that were assessed by the U.S. Geological Survey for carbon dioxide storage. See 

figure 2.
National Assessment of Geologic 

Carbon Dioxide Storage Resources—

Results

By U.S. Geological Survey Geologic Carbon Dioxide Storage Resources 

Assessment Team

Circular 1386

Version 1.1, September 2013

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

Version 1.0 was released June 26, 2013

Version 1.1 was released September 2013

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Suggested citation:

U.S. Geological Survey Geologic Carbon Dioxide Storage Resources Assessment Team, 2013, National assessment of 

geologic carbon dioxide storage resources—Results (ver. 1.1, September 2013): U.S. Geological Survey Circular 1386, 

41 p., http://pubs.usgs.gov/circ/1386/. (Supersedes ver. 1.0 released June 26, 2013.)

Compact disc:

The printed U.S. Geological Survey Circular 1386 has a CD-ROM in the pocket on its inside back cover 

that contains the digital Circular plus two related reports: USGS Data Series 774 and USGS Fact Sheet 

2013–3020.

ISBN 978-1-4113-3636-0
iii

Acknowledgments

We wish to thank the following State scientific agencies and universities for contributing data 

and input that aided in this assessment: Geological Survey of Alabama; Alaska Division of 

Geological and Geophysical Surveys; Alaska Division of Oil and Gas; Arizona Geological Survey; 

California Geological Survey; Colorado Geological Survey; Florida Geological Survey; Georgia 

State University, Department of Geosciences; Idaho Geological Survey; Illinois State Geological Survey; Indiana Geological Survey; Kansas Geological Survey; Kentucky Geological Survey; 

Louisiana Geological Survey; Maine Geological Survey; Maryland Geological Survey; Western 

Michigan University, Department of Geosciences; Minnesota Geological Survey; Mississippi 

Department of Environmental Quality Office of Geology; Missouri Department of Natural 

Resources Division of Geology and Land Survey; Montana Bureau of Mines and Geology; New 

Hampshire Geological Survey; New Jersey Geological and Water Survey; New Mexico Bureau 

of Geology and Mineral Resources; New York State Geological Survey; North Carolina Geological Survey; North Dakota Geological Survey; Ohio Department of Natural Resources, Division of 

Geological Survey; Oklahoma Geological Survey; Pennsylvania Department of Conservation and 

Natural Resources, Bureau of Topographic and Geologic Survey; Tennessee Department of Environment and Conservation, Division of Geology; University of Tennessee at Knoxville, Department of Earth and Planetary Sciences; Texas Bureau of Economic Geology; University of Texas 

at Austin; Utah Geological Survey; Vermont Geological Survey; Virginia Department of Mines, 

Minerals, and Energy, Division of Geology and Mineral Resources; West Virginia Geological and 

Economic Survey; and Wisconsin Geological and Natural History Survey. We also wish to thank 

the Geological Survey of Canada for contributing data and results that aided in this assessment.

We thank all of the participants in the July 16–18, 2012, Storage Efficiency Workshop in Austin, 

Texas, particularly Susan Hovorka and the members of the Gulf Coast Carbon Center, Bureau of 

Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, for their 

help in facilitating the workshop. John Wicks and Nathanael Barta (independent geologists) 

provided valuable advice related to regional geology. We also appreciate discussions with members of the U.S. Department of Energy National Energy Technology Laboratory, particularly John 

Litynski and Angela Goodman, and with members of the U.S. Environmental Protection Agency 

Underground Injection Control Program, particularly Bruce Kobelski.

We thank the following current and former U.S. Geological Survey (USGS) employees for sharing 

their expertise and data products related to regional geology and petroleum engineering: Lawrence Anna, Emil Attanasi, Kenneth Bird, Russell Dubiel, Donald Gautier, Debra Higley, David 

Houseknecht, Alexander Karlsen, Mark Kirschbaum, Robert Milici, Philip Nelson, Ofori Pearson, 

Robert Ryder, Joseph Smoot, Sharon Swanson, and Christopher Swezey. The content and presentation of this report benefited greatly from the technical reviews by Robert Burruss, Douglas Duncan, David Houseknecht, and Leslie Ruppert. Jeannette Foltz, Elizabeth Good, Angela 

Hall, Thomas Judkins, Harry Lerch, and Katharine Schindler assisted us during the publication 

process. Project management was greatly assisted by Adrienne Bartlewitz, James Coleman, 

Douglas Duncan, Matthew Larsen, Harry Lerch, Linda McDonnell, Shirlie McManus-Hunt, and 

Brenda Pierce.
iv

Members of the U.S. Geological Survey 

Geologic Carbon Dioxide Storage Resources 

Assessment Team1

Peter D. Warwick, Project Chief

Madalyn S. Blondes

Sean T. Brennan

Marc L. Buursink

Steven M. Cahan

James L. Coleman

Troy A. Cook

Margo D. Corum

Jacob A. Covault

William H. Craddock

Christina A. DeVera

Colin Doolan

Ronald M. Drake II

Lawrence J. Drew

Joseph A. East

Philip A. Freeman

Christopher P. Garrity

Kevin J. Gooley

Mayur A. Gosai

Hossein Jahediesfanjani2

Celeste D. Lohr

John C. Mars

Matthew D. Merrill

Ricardo A. Olea

Tina L. Roberts-Ashby

William A. Rouse

Paul G. Schruben

John H. Schuenemeyer2

Ernie R. Slucher

Brian A. Varela

Mahendra K. Verma

1

All members are or were with the U.S. Geological Survey unless otherwise indicated.

2

Contractor.
v

Contents

Acknowledgments........................................................................................................................................iii

Members of the U.S. Geological Survey Geologic Carbon Dioxide Storage Resources 

Assessment Team ...........................................................................................................................iv

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Storage Assessment Units...........................................................................................................................3

Study Areas.....................................................................................................................................................3

Buoyant and Residual Trapping...................................................................................................................8

Assessment Categories................................................................................................................................9

Data Sources..................................................................................................................................................9

Assessment Process.....................................................................................................................................9

Assessment Assumptions and Constraints......................................................................................9

Resource Calculations.......................................................................................................................10

Aggregation .........................................................................................................................................11

Results of the Assessment of Technically Accessible Storage Resources.......................................12

Buoyant Trapping Storage.................................................................................................................12

Residual Trapping Storage................................................................................................................12

Petroleum Reservoirs.........................................................................................................................12

Discussion of Results..................................................................................................................................12

Comparison of Results with Findings from Previous Assessments ....................................................17

Conclusions...................................................................................................................................................17

References Cited..........................................................................................................................................18

Glossary.........................................................................................................................................................21

Figures

1. Pie charts showing mean estimates by the U.S. Geological Survey in 2012 

of technically accessible storage resources (TASR) for carbon dioxide (CO2) 

in the United States by (A) type and class and (B) region.....................................................3

2. Map of the conterminous United States and Alaska showing 8 regions 

(separated by bold dashed lines and labeled in a bold font), evaluated areas 

(bluish gray) that were not assessed, and 36 areas (pattern) that were 

assessed by the U.S. Geological Survey for carbon dioxide (CO2) storage........................4

3. Graph showing the range estimated by the U.S. Geological Survey in 2012 

for the technically accessible storage resource (TASR) for carbon dioxide (CO2) 

in each assessed basin in the United States ...........................................................................5

4. Schematic cross section through a storage assessment unit (SAU) 

illustrating the relation between buoyant and residual trapping types 

in the storage formation (SF) ......................................................................................................8

5. Flow diagram of the key steps for calculating known recovery replacement 

storage resources (KRRSR), buoyant trapping storage resources (BSR), 

residual trapping storage resources (R1SR, R2SR, R3SR), and technically 

accessible storage resources (TASR).......................................................................................11
vi

6. Graphs showing empirical cumulative distribution function (CDF) plots 

of all six categories of technically accessible storage resources (TASR) 

for carbon dioxide in the United States, exclusive of federally owned 

offshore areas .............................................................................................................................13

7. Pie charts showing mean estimates of technically accessible storage 

resources (TASR) for carbon dioxide (CO2) in selected regions of the 

United States ...............................................................................................................................14

8. Pie charts showing mean estimates of (A) buoyant trapping storage 

resources and (B) residual trapping class 2 storage resources for 

carbon dioxide (CO2) in the United States, by region............................................................16

Tables

1. Estimates by the U.S. Geological Survey in 2012 of national totals for 

technically accessible storage resources (TASR) for carbon dioxide (CO2) 

in the United States by resource type and class.....................................................................2

2. Estimates by the U.S. Geological Survey in 2012 of basin and regional totals 

for technically accessible storage resources (TASR) for carbon dioxide (CO2) 

in the United States ......................................................................................................................6

3. Estimates by the U.S. Geological Survey in 2012 of basin and storage 

assessment unit (SAU) totals for technically accessible storage 

resources (TASR) for carbon dioxide (CO2) in the United States..........................................25

4. Mean estimates by the U.S. Geological Survey in 2012 for technically 

accessible storage resources (TASR) for carbon dioxide (CO2) in deep 

storage assessment units (SAUs) in the United States........................................................17
vii

Conversion Factors

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

mile, nautical (nmi) 1.852 kilometer (km)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

Area

square inch (in2) 6.452 square centimeter (cm2)

Volume

gallon (gal) 3.785 liter (L)

barrel (bbl), (petroleum, 1 barrel 

= 42 gal)

0.1590 cubic meter (m3)

cubic foot (ft3) 0.02832 cubic meter (m3)

liter (L) 0.2642 gallon (gal)

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg)

ton, short (2,000 lb) 0.9072 megagram (Mg)

ton, long (2,240 lb) 1.016 megagram (Mg)

milligram (mg) 0.00003527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound, avoirdupois (lb)

megagram (Mg) = 1 metric ton 

(t) (1,000 kg)

1.102 ton, short (2,000 lb)

megagram (Mg) 0.9842 ton, long (2,240 lb)

million metric tons = megaton 

(Mt)

1.102 million short tons

billion metric tons = gigaton (Gt) 1.102 billion short tons

Pressure

bar 100 kilopascal (kPa)

pound-force per square inch 

(lbf/in2 or psi)

6.895 kilopascal (kPa)

kilopascal (kPa) 0.01 bar

kilopascal (kPa) 0.1450 pound-force per square inch 

(lbf/in2)

Pressure gradient

pound-force per square inch per 

foot (lbf/in2/ft or psi/ft)

22.62 kilopascal per meter (kPa/m)

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L).

Permeability is given in darcies (D) and millidarcies (mD).

1 barrel of oil equivalent (BOE) = 1 barrel of crude oil (42 gallons)

= 6,000 cubic feet of natural gas

= 1.5 barrels of natural gas liquids
viii

Abbreviations, Acronyms, and Symbols

ASF area of the storage formation within the storage assessment unit

BPV buoyant trapping pore volume

BSE buoyant trapping storage efficiency

BSR buoyant trapping storage resource

BSV buoyant trapping storage volume

bbl petroleum barrel or barrels

BOE barrel of oil equivalent

BOEM Bureau of Ocean Energy Management

CDF cumulative distribution function

CO2 carbon dioxide

D darcy

DOE U.S. Department of Energy

EPA U.S. Environmental Protection Agency

FVF formation volume factor

GOR gas:oil ratio

Gt gigaton = billion metric tons

k permeability

KRRES known recovery production volumes converted to reservoir conditions

KRRSR known recovery replacement storage resource

LCU Lower Cretaceous unconformity

mD millidarcy

Mt megaton = million metric tons

NETL National Energy Technology Laboratory

NOGA USGS National Oil and Gas Assessment

NQ nonquantitative

P5 probability percentile—5-percent probability that the true value is less than the 

given value

P50 probability percentile—50-percent probability that the true value is less than the 

given value. P50 is the median of the probability distribution.

P95 probability percentile—95-percent probability that the true value is less than the 

given value

psi pound-force per square inch
ix

RPV residual trapping pore volume

RW the area fraction of the SAU available for storage after consideration of EPA waterquality guidelines or highly fractured seals

R1PV residual trapping class 1 pore volume

R1SE residual trapping class 1 storage efficiency

R1SR residual trapping class 1 storage resource

R1SV residual trapping class 1 storage volume

R2PV residual trapping class 2 pore volume

R2SE residual trapping class 2 storage efficiency

R2SR residual trapping class 2 storage resource

R2SV residual trapping class 2 storage volume

R3PV residual trapping class 3 pore volume

R3SE residual trapping class 3 storage efficiency

R3SR residual trapping class 3 storage resource

R3SV residual trapping class 3 storage volume

Ri residual trapping injectivity classes 1, 2, or 3

RiSE residual trapping storage efficiencies for classes 1, 2, or 3

SAU storage assessment unit used in this assessment

SF storage formation

SFPV storage formation pore volume

TPI thickness of the net porous interval

TASR technically accessible storage resource

TASV technically accessible storage volume

TDS total dissolved solids

TPS total petroleum system

USDW underground source of drinking water

USGS U.S. Geological Survey

CO 2 density of carbon dioxide

 porosity

 PI porosity of the net porous interval

National Assessment of Geologic Carbon Dioxide Storage 

Resources—Results

By U.S. Geological Survey Geologic Carbon Dioxide Storage Resources Assessment Team

Abstract

In 2012, the U.S. Geological Survey (USGS) completed 

an assessment of the technically accessible storage resources 

(TASR) for carbon dioxide (CO2) in geologic formations underlying the onshore and State waters area of the United States. 

The formations assessed are at least 3,000 feet (914 meters) 

below the ground surface. The TASR is an estimate of the CO2

storage resource that may be available for CO2 injection and 

storage that is based on present-day geologic and hydrologic 

knowledge of the subsurface and current engineering practices. Individual storage assessment units (SAUs) for 36 basins 

were defined on the basis of geologic and hydrologic characteristics outlined in the assessment methodology of Brennan 

and others (2010, USGS Open-File Report 2010–1127) and 

the subsequent methodology modification and implementation 

documentation of Blondes, Brennan, and others (2013, USGS 

Open-File Report 2013–1055). The mean national TASR is 

approximately 3,000 metric gigatons (Gt). The estimate of the 

TASR includes buoyant trapping storage resources (BSR), where 

CO2 can be trapped in structural or stratigraphic closures, and 

residual trapping storage resources, where CO2 can be held in 

place by capillary pore pressures in areas outside of buoyant 

traps. The mean total national BSR is 44 Gt. The residual storage resource consists of three injectivity classes based on reservoir permeability: residual trapping class 1 storage resource 

(R1SR) represents storage in rocks with permeability greater 

than 1 darcy (D); residual trapping class 2 storage resource 

(R2SR) represents storage in rocks with moderate permeability, 

defined as permeability between 1 millidarcy (mD) and 1 D; 

and residual trapping class 3 storage resource (R3SR) represents 

storage in rocks with low permeability, defined as permeability 

less than 1 mD. The mean national storage resources for rocks 

in residual trapping classes 1, 2, and 3 are 140 Gt, 2,700 Gt, 

and 130 Gt, respectively. The known recovery replacement 

storage resource (KRRSR) is a conservative estimate that represents only the amount of CO2

 at subsurface conditions that 

could replace the volume of known hydrocarbon production. 

The mean national KRRSR, determined from production volumes rather than the geologic model of buoyant and residual 

traps that make up TASR, is 13 Gt. The estimated storage 

resources are dominated by residual trapping class 2, which 

accounts for 89 percent of the total resources. The Coastal 

Plains Region of the United States contains the largest storage 

resource of any region. Within the Coastal Plains Region, the 

resources from the U.S. Gulf Coast area represent 59 percent 

of the national CO2 storage capacity.

Introduction

Carbon dioxide (CO2) is the primary greenhouse gas 

that is contributing to recent global climate change, and fossil 

fuel combustion is a major source of CO2 emissions to the 

atmosphere (Intergovernmental Panel on Climate Change, 

2001; U.S. Environmental Protection Agency, 2013). The U.S. 

Energy Information Administration (2012a,b) estimated that 

the annual energy-related CO2 emissions in the United States 

during 2011 were 5.5 billion metric tons (gigatons, Gt) and 

projected that fossil fuel combustion will supply the dominant 

portion of total global energy demand in both industrialized 

and developing countries for the next few decades. The overall 

reduction of CO2 emissions will likely involve some combination of technologies, but for the immediate future, industrial 

capture and sequestration (storage) of CO2 in geologic reservoirs is an available technology because existing knowledge 

derived from the oil and gas production industries has helped 

to solve some of the major engineering challenges. A detailed 

estimate of the national geologic CO2 storage resources is 

required to make informed decisions about the implementation 

of geologic CO2 sequestration in the United States.

In 2007, the Energy Independence and Security Act 

(Public Law 110–140; U.S. Congress, 2007) directed the U.S. 

Geological Survey (USGS) to conduct a national assessment 

of geologic storage resources for CO2 in consultation with 

the U.S. Environmental Protection Agency (EPA), the U.S. 

Department of Energy (DOE), and State geological surveys. 

From 2008 to 2009, the USGS developed a preliminary 

methodology to estimate storage resource potential that may 

be applied uniformly to geologic formations across the United 

States (Burruss and others, 2009). This methodology was 

reviewed by the public and a panel of experts, and revisions 
2 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

were incorporated into a final assessment methodology by 

Brennan and others (2010). During the implementation phase 

of the assessment (from 2010 to 2012), several practical steps 

were added to the assessment methodology of Brennan and 

others (2010). The details of the methodology used in the 

assessment are described in Blondes, Brennan, and others 

(2013).

The purpose of this report is to present the results of the 

USGS national assessment of geologic CO2 storage resources, 

which was completed in 2012 (table 1; fig. 1A,B). The goal 

of this project was to conduct an initial assessment of storage 

capacity on a regional basis, and results are not intended for 

use in the evaluation of specific sites for potential CO2 storage. 

The national assessment is a geology-based examination of 

all sedimentary basins in the onshore and State waters area of 

the United States that contain storage assessment units (SAUs) 

that could be defined following the methodology outlined in 

Brennan and others (2010) and Blondes, Brennan, and others 

(2013) (figs. 2, 3; table 2). Although geologic storage of CO2

may be possible in some areas not assessed by the USGS, the 

SAUs identified in this assessment represent those areas within 

sedimentary basins that met the assessment criteria. A geologic 

description of each SAU was prepared during the assessment; 

descriptions of SAUs in several basins are in the basin report 

series, “Geologic Framework for the National Assessment of 

Carbon Dioxide Storage Resources,” edited by Warwick and 

Corum (2012).

Two other reports are being published with this assessment results report, and the reader should refer to them for 

additional information. The U.S. Geological Survey Geologic Carbon Dioxide Storage Resources Assessment Team’s 

(2013a) data report contains (1) individual SAU assessment 

forms with all input parameters and details on the allocation 

of the SAU surface land area by State and general landownership category; (2) figures representing the distribution 

of all storage classes for each SAU; (3) a comprehensive data 

table containing most input data and assessment result values 

for each SAU, and (4) a pairwise correlation matrix specifying 

geological and methodological dependencies between SAUs 

that are needed for aggregation of results. The U.S. Geological 

Survey Geologic Carbon Dioxide Storage Resources Assessment Team’s (2013b) Fact Sheet summarizes the final results 

of this assessment.

This assessment does not include an estimate of the CO2

storage potential in “unmineable coal seams” because no 

standard definition indicates which coal seams are unmineable 

(Brennan and others, 2010). Nor does this assessment include 

estimates of the potential for CO2 storage in unconventional or 

continuous reservoirs such as shale, low-permeability “tight” 

sandstone, or basaltic rocks. Little is known about the largescale CO2

 storage potential in these unconventional reservoirs, 

and USGS assessment methodologies still need to be developed to address these types of resources (Jones and others, 

2012).

Table 1. Estimates by the U.S. Geological Survey in 2012 of national totals for technically accessible storage resources (TASR) for 

carbon dioxide (CO2) in the United States by resource type and class.

[Estimates are in billions of metric tons (gigatons, Gt). P5, P50, and P95 are probability percentiles and represent the 5-, 50-, and 95-percent probabilities, respectively, that the true storage resource is less than the value shown. The terminology used in this report differs from that used by the petroleum industry and 

follows standard statistical practice (for example, Everitt and Skrondal, 2010), where percentiles, or fractiles, represent the value of a variable below which a 

certain proportion of observations falls. The percentiles were calculated by using the aggregation method described in the “Aggregation” section of this report 

and in Blondes, Schuenemeyer, and others (2013). Percentile values do not sum to totals because the aggregation procedure used partial dependencies between 

storage assessment units. The P50 (median) values are generally less than mean values because most output distributions are right skewed. The known recovery 

replacement storage resource (KRRSR) is listed separately as determined from petroleum production volumes; the same type of resource is also included in the 

buoyant storage type estimated from a geologic model. Mean values sum to totals but are reported to only two significant figures]

CO2 storage resource type and class P5 P50 P95 Mean

Symbol Name

Storage resource estimated from geologic models

BSR Buoyant trapping storage resource 19 31 110 44

R1SR Residual trapping class 1 storage resource 97 140 200 140

R2SR Residual trapping class 2 storage resource 2,100 2,600 3,300 2,700

R3SR Residual trapping class 3 storage resource 58 120 230 130

TASR (total) Technically accessible storage resource 2,300 3,000 3,700 3,000

Storage resource estimated from petroleum production volumes

KRRSR Known recovery replacement storage resource 11 13 15 13
Study Areas 3

Storage Assessment Units

The SAU is a mappable volume of rock that consists of 

a porous reservoir and a bounding regional sealing formation (Brennan and others, 2010). Within the SAU, the porous 

reservoir is defined as the storage formation (SF). A schematic 

cross section that extends downdip through a hypothetical 

SAU is shown in figure 4. The parts of the SF that contain 

buoyant trapping storage resources and residual trapping storage resources are shown in color (fig. 4).

The extent of the SF is defined, in part, by the physical properties of CO2

. The upper vertical limit chosen by 

Brennan and others (2010) for this assessment was 3,000 feet 

(914 meters) because CO2 at this depth is typically subjected 

to temperatures and pressures that maintain the CO2 in a supercritical state and maximize the storage resource per unit volume. Supercritical CO2

 has density values much higher than 

those of gaseous CO2 (Lemmon and others, 2009). The lower 

vertical limit for the SAU of 13,000 ft (3,962 m) is based 

on the potential CO2 injection depth at pipeline pressures 

without additional compression at the surface. The rationale 

for these limits was discussed in more detail by Burruss and 

others (2009). All SAUs between depths of 3,000 ft (914 m) 

and 13,000 ft (3,962 m) are referred to as standard SAUs. 

If reservoir rock properties suggested that a viable storage 

resource is present at depths below 13,000 ft (3,962 m), the 

assessment geologist may have added an additional deep SAU

for this deeper reservoir. The areal extent of the SAU on a map 

is defined by contours showing depths from the surface to the 

top of the SF.

Study Areas

Sedimentary rocks of deep saline formations and of existing oil and gas fields were evaluated. Specifically, 33 sedimentary basins, or combined basin areas, within 8 regions of the 

United States were assessed (fig. 1B, table 2). Numerous other 

basins (study areas shown in bluish gray in fig. 2) were evaluated but not assessed because existing geologic conditions and 

available data indicated that the areas failed to meet the minimum requirements for CO2

 storage as outlined in Brennan and 

others (2010). Within the assessed basins, a total of 202 SAUs 

(table 3, at back of report) were identified as having good storage potential because of the presence of a robust regional seal, 

adequate reservoir rock, and sufficient areas containing saline 

formation waters. Ten of the SAUs did not have sufficient data 

to build a robust geologic model to accurately estimate the 

storage resource and were designated as nonquantitative SAUs 

(table 3). No storage resources were estimated for the 10 

nonquantitative SAUs; surficial geographic boundaries were 

defined and geologic descriptions were prepared.

Figure 1. Pie charts showing mean estimates by the U.S. 

Geological Survey in 2012 of technically accessible storage 

resources (TASR) for carbon dioxide (CO2) in the United States 

by (A) type and class and (B) region. Resources were estimated 

for eight geographic regions shown in figure 2. A mean total of 

3,000 metric gigatons (Gt) of storage resources was estimated to 

exist in buoyant and residual storage types. The known recovery 

replacement storage resource (KRRSR) is not shown in part A but 

is included in the buoyant storage type. Resources in federally 

owned offshore areas were not assessed. Mean values sum to 

totals but are reported to only two significant figures. Percentages 

were calculated from unrounded resource estimates.

Buoyant storage

(44 Gt)

2%

Residual, class 2

(2,700 Gt)

89%

Residual, class 3

(130 Gt)

4%

Residual, class 1

(140 Gt)

5%

A

Alaska

(270 Gt)

9%

Pacific Northwest

(14 Gt)

<1% California

(90 Gt)

3% Western

Mid-Continent 

(150 Gt)

5%

Eastern Mesozoic

Rift Basins

(0.44 Gt)

<1%

Rocky Mountains 

and Northern 

Great Plains

(270 Gt)

9%

Eastern

Mid-Continent 

(230 Gt)

8%

Coastal Plains

(1,900 Gt)

65%

B
4 National Assessment of Geologic Carbon Dioxide Storage Resources—Results 70°W 80°W 90°W 100°W 110°W 120°W 40°N 30°N 140°W 160°W 65°N

60°N55°N

180°W

Assessed areaEvaluated area

EXPLANATION KILOMETERS 1,000 750 500 250 0

500 MILES 250 0 KILOMETERS 500 250 0

0 250 MILES

Pacific

Northwest

Rocky Mountains

and Northern

Great Plains

Western

Mid-Continent Eastern Mesozoic Rift Basins Eastern Mid-Continent

Coastal Plains

Alaska

California

Bighorn Basin

Powder

River

Basin

Wind River Basin

Greater Green

River Basin

Hanna, 

Laramie, and 

Shirley Basins

Western

Oregon and Washington

Basins

Columbia Basin of 

Oregon, Washington, 

and Idaho

Wyoming–Idaho–Utah 

Thrust Belt

Alaska 

North Slope

Kandik 

Basin

U.S. Gulf Coast

Bend Arch

and Fort

Worth Basin

Arkoma Basin

Denver 

Basin

Anadarko and Southern 

Oklahoma Basins

Eastern 

Great 

Basin

Sacramento

Basin

San 

Joaquin 

Basin Central 

California 

Coast Basins

Ventura 

Basin

Los Angeles 

Basin

Uinta and Piceance Basins

Paradox 

Basin

San Juan

Basin

Raton 

Basin

Williston 

Basin

Illinois 

Basin

Michigan 

Basin

South Florida 

Basin

Black 

Warrior 

Basin

Appalachian 

Basin

Kansas 

Basins

Palo Duro 

Basin

Permian Basin

Eastern 

Mesozoic 

Rift Basins

Atlantic 

Coastal Plain

Base map from Jarvis

and others (2008)

CGIAR-Consortium

for Spatial Information

SRTM 90m Database

Figure 2. Map of the conterminous United States and Alaska showing 8 regions (separated by bold dashed lines and labeled in a bold font), evaluated areas (bluish gray) that were not assessed, and 36 areas (pattern) that were assessed by the U.S. Geological Survey for carbon dioxide (CO2) storage. The assessed areas contain multiple storage assessment units 

(SAUs). Resources in federally owned offshore areas were not assessed, and Hawaii was considered unlikely to have significant storage resources. Regions and study areas are plotted over a shaded-relief image showing higher elevations in brown and tan and lower elevations in green.
Study Areas 

5

Figure 3. Graph showing the range estimated by the U.S. Geological Survey in 2012 for the technically accessible storage resource (TASR) for carbon dioxide (CO2) in each assessed basin in the United States. Estimates are in millions of metric tons (Mt). Each center dot represents the mean storage resource. The lower bound is the P5 percentile, representing a 

5-percent probability that the true storage resource is less than the value shown. The upper bound is the P95 percentile, representing a 95-percent probability that the true storage resource is less than the value shown. Values are presented on a logarithmic scale. Basins are shown in figure 2, and resource estimates are summarized in table 2.

Eastern Great Basin Black Warrior Basin Kansas Basins Eastern Mesozoic Rift Basins San Juan Basin Kandik Basin Bighorn Basin Hanna, Laramie, and Shirley Basins Paradox Basin Denver Basin Los Angeles Basin Uinta and Piceance Basins Ventura Basin Palo Duro Basin Wind River Basin Arkoma Basin Western Oregon and Washington Basins Atlantic Coastal Plain Bend Arch and Fort Worth Basin Powder River Basin Appalachian Basin Sacramento Basin Greater Green River Basin Wyoming-Idaho-Utah Thrust Belt San Joaquin Basin Michigan Basin Permian Basin Anadarko and Southern Oklahoma Basins Williston Basin Illinois Basin South Florida Basin Alaska North Slope U.S. Gulf Coast

TA

RS , in millions of metric tons (Mt)

10,000,000

1,000,000

100,000

10,000

1,000

100

10
6 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Table 2. Estimates by the U.S. Geological Survey in 2012 of basin and regional totals for technically accessible storage resources 

(TASR) for carbon dioxide (CO2) in the United States.

[Estimates are in millions of metric tons (megatons, Mt). P5, P50, and P95 are probability percentiles and represent the 5-, 50-, and 95-percent probabilities, 

respectively, that the true storage resource is less than the value shown. The percentiles were calculated by using the aggregation method described in the 

“Aggregation” section of this report and in Blondes, Schuenemeyer, and others (2013). Percentile values do not sum to totals because the aggregation procedure used partial dependencies between storage assessment units. Mean values sum to totals but are reported to only two significant figures if the value is 

greater than 1 Mt and are rounded to the nearest 0.1 Mt if the value is less than 1 Mt. Regions are listed from northwest to east; basins are listed alphabetically]

Basin name

KRRSR

Known recovery replacement 

storage resource

BSR

Buoyant trapping 

storage resource

R1SR

Residual trapping class 1 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean 

Alaska Region 

Alaska North Slope 700 910 1,100 910 2,400 8,600 62,000 18,000 510 770 1,100 790 

Kandik Basin 0.0 0.0 0.0 0.0 1.1 13 150 38 0.0 0.0 0.0 0.0 

Aggregated totals 700 910 1,100 910 2,400 8,600 62,000 18,000 510 770 1,100 790 

Pacific Northwest Region 

Western Oregon and Washington 

Basins 0.0 0.0 0.0 0.0 0.1 1.5 35 8.2 860 1,600 2,700 1,700 

Aggregated totals 0.0 0.0 0.0 0.0 0.1 1.5 35 8.2 860 1,600 2,700 1,700 

California Region 

Los Angeles Basin 10 13 16 13 43 75 140 81 66 130 230 130 

Sacramento Basin 34 48 67 49 42 57 180 80 460 740 1,100 760 

San Joaquin Basin 18 24 32 25 31 98 980 270 1,600 2,400 3,400 2,500 

Ventura Basin 23 32 43 32 29 52 290 93 76 160 300 170 

Aggregated totals 94 120 150 120 180 320 1,500 520 2,500 3,500 4,700 3,500 

Rocky Mountains and Northern Great Plains Region 

Bighorn Basin 75 93 110 93 89 120 290 150 0.0 0.0 0.0 0.0 

Denver Basin 76 100 130 100 110 170 850 300 35 100 250 120 

Eastern Great Basin 0.9 1.2 1.6 1.2 1.2 2.2 23 6.6 0.0 0.0 0.0 0.0 

Greater Green River Basin 380 500 650 500 440 580 1,500 740 0.0 0.0 0.0 0.0 

Hanna, Laramie, and Shirley Basins 0.9 1.1 1.4 1.1 17 74 370 120 5.2 12.0 23 12 

Paradox Basin 36 51 71 52 45 63 160 78 0.0 0.0 0.0 0.0 

Powder River Basin 96 120 150 120 120 180 710 280 0.3 1.8 4.1 2.0 

San Juan Basin 9.4 12 16 12 11 15 37 19 3.8 8.4 17 9.1 

Uinta and Piceance Basins 46 58 75 59 47 73 280 110 0.0 0.0 0.0 0.0 

Williston Basin 150 180 230 180 340 710 2,000 880 1,600 2,700 4,400 2,800 

Wind River Basin 52 66 81 66 63 86 280 130 0.6 1.4 3.3 1.6 

Wyoming-Idaho-Utah Thrust Belt 240 310 390 310 290 370 600 400 0.0 0.0 0.0 0.0 

Aggregated totals 1,300 1,500 1,800 1,500 1,800 2,700 6,300 3,200 1,700 2,900 4,600 3,000 

Western Mid-Continent Region 

Anadarko and Southern Oklahoma 

Basins 220 300 420 310 1,000 1,400 3,300 1,700 450 920 1,700 990 

Arkoma Basin 3.7 5.2 7.3 5.3 14 25 66 31 0.0 0.0 0.0 0.0 

Bend Arch and Fort Worth Basin 210 290 370 290 230 310 500 340 330 660 1,100 680 

Kansas Basins 4.5 5.6 6.9 5.7 4.8 6.1 9.2 0.0 0.0 0.0 0.0 0.0 

Palo Duro Basin 120 150 190 150 1.6 4.1 32 9.3 72 110 170 120 

Permian Basin 1,000 1,300 1,700 1,300 1,600 2,000 4,000 2,400 2,200 3,900 6,700 4,100 

Aggregated totals 1,700 2,100 2,500 2,100 3,100 3,800 7,800 4,500 3,600 5,700 8,900 5,900 

Eastern Mid-Continent Region 

Appalachian Basin 21 28 37 28 38 79 370 130 160 270 440 280 

Black Warrior Basin 14 23 32 23 13 17 30 19 0.0 0.0 0.0 0.0 

Illinois Basin 69 85 100 85 94 290 1,300 440 900 1,400 2,300 1,500 

Michigan Basin 140 180 220 180 190 280 790 360 2,800 4,500 6,800 4,600 

Aggregated totals 260 310 370 320 380 740 2,200 940 4,100 6,200 9,100 6,400 

Coastal Plains Region 

Atlantic Coastal Plain 0.0 0.0 0.0 0.0 39 100 270 120 2,000 3,100 4,700 3,200 

South Florida Basin 6.7 8.5 10 8.5 21 97 900 240 0.0 0.0 0.0 0.0 

U.S. Gulf Coast 6,400 8,000 9,800 8,000 7,800 11,000 39,000 16,000 75,000 120,000 170,000 120,000 

Aggregated totals 6,400 8,000 9,900 8,000 8,000 11,000 40,000 17,000 78,000 120,000 180,000 120,000 

Eastern Mesozoic Rift Basins Region 

Eastern Mesozoic Rift Basins 0.0 0.0 0.0 0.0 1.3 2.0 19 5.9 0.0 0.0 0.0 0.0 

Aggregated totals 0.0 0.0 0.0 0.0 1.3 2.0 19 5.9 0.0 0.0 0.0 0.0 
Study Areas 7

Table 2. Estimates by the U.S. Geological Survey in 2012 of basin and regional totals for technically accessible storage resources 

(TASR) for carbon dioxide (CO2) in the United States.—Continued

R2SR

Residual trapping class 2 

storage resource

R3SR

Residual trapping class 3 

storage resource

TASR

Technically accessible 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean

Alaska Region—Continued

150,000 200,000 280,000 210,000 7,600 38,000 110,000 45,000 170,000 260,000 400,000 270,000

480 1,100 2,200 1,200 22 170 630 230 570 1,400 2,700 1,500

150,000 200,000 280,000 210,000 7,700 39,000 110,000 45,000 180,000 260,000 410,000 270,000

Pacific Northwest Region—Continued

6,600 12,000 20,000 12,000 0.6 10 43 14 7,500 14,000 22,000 14,000

6,600 12,000 20,000 12,000 0.6 10 43 14 7,500 14,000 22,000 14,000

California Region—Continued

2,000 3,300 5,600 3,500 0.1 1.6 6.2 2.2 2,200 3,500 5,800 3,700

19,000 28,000 39,000 29,000 0.0 2.3 10 3.2 20,000 29,000 40,000 29,000

33,000 48,000 65,000 48,000 25 120 300 130 36,000 51,000 69,000 51,000

3,100 5,500 9,200 5,700 0.5 9.0 35 12 3,200 5,700 9,600 6,000

63,000 85,000 110,000 86,000 35 130 320 150 67,000 90,000 120,000 90,000

Rocky Mountains and Northern Great Plains Region—Continued

890 1,500 2,400 1,500 21 86 230 100 1,100 1,700 2,800 1,800

1,000 2,700 5,900 3,000 37 210 830 300 1,400 3,300 7,200 3,700

80 170 360 190 1.9 24 97 34 98 210 430 230

21,000 30,000 43,000 31,000 1,700 6,200 17,000 7,400 26,000 38,000 57,000 39,000

1,100 2,000 3,200 2,100 25 91 240 110 1,300 2,200 3,600 2,300

1,000 2,500 5,300 2,800 28 380 1,600 530 1,300 3,100 6,300 3,400

11,000 17,000 25,000 18,000 39 170 510 210 11,000 18,000 26,000 18,000

380 640 1,100 670 5.2 30 94 37 430 710 1,200 740

1,300 2,200 3,300 2,200 290 1,200 3,300 1,400 2,000 3,500 6,300 3,800

99,000 140,000 180,000 140,000 1,100 5,200 14,000 6,000 110,000 140,000 190,000 150,000

4,100 7,100 11,000 7,300 150 580 1,500 670 4,600 7,800 12,000 8,100

26,000 39,000 55,000 39,000 780 3,800 12,000 4,700 28,000 43,000 63,000 44,000

180,000 240,000 310,000 240,000 7,300 19,000 43,000 22,000 200,000 270,000 350,000 270,000

Western Mid-Continent Region—Continued

34,000 55,000 88,000 57,000 670 2,500 6,100 2,800 38,000 60,000 96,000 62,000

3,500 7,000 13,000 7,400 39 360 1,300 480 3,800 7,500 13,000 7,900

7,000 13,000 20,000 13,000 170 1,100 3,800 1,400 8,600 15,000 24,000 15,000

160 280 480 300 1.5 12 48 17 180 300 510 320

4,900 6,900 9,400 7,000 9.0 56 170 67 5,100 7,100 9,600 7,200

31,000 48,000 75,000 50,000 460 2,200 6,400 2,600 37,000 57,000 89,000 59,000

93,000 130,000 190,000 130,000 2,600 6,800 15,000 7,500 110,000 150,000 210,000 150,000

Eastern Mid-Continent Region—Continued

13,000 18,000 27,000 19,000 180 840 2,500 1,000 14,000 20,000 29,000 20,000

170 280 450 290 0.2 2.1 7.2 2.7 180 300 480 310

110,000 140,000 200,000 150,000 1,000 5,100 14,000 6,100 110,000 150,000 210,000 150,000

33,000 47,000 66,000 48,000 560 3,300 11,000 4,200 40,000 56,000 78,000 57,000

160,000 210,000 280,000 210,000 2,700 9,900 25,000 11,000 170,000 230,000 300,000 230,000

Coastal Plains Region—Continued

6,900 11,000 16,000 11,000 0.0 0.1 4.7 1.1 9,200 14,000 20,000 14,000

120,000 160,000 200,000 160,000 1,400 7,600 21,000 9,000 120,000 160,000 210,000 170,000

1,100,000 1,600,000 2,200,000 1,600,000 6,600 30,000 83,000 35,000 1,300,000 1,700,000 2,400,000 1,800,000

1,300,000 1,700,000 2,400,000 1,800,000 11,000 38,000 96,000 44,000 1,400,000 1,900,000 2,600,000 1,900,000

Eastern Mesozoic Rift Basins Region—Continued

130 280 510 290 7.6 100 410 140 180 400 830 440

130 280 510 290 7.6 100 410 140 180 400 830 440
8 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Figure 4. Schematic cross section through a storage 

assessment unit (SAU) illustrating the relation between buoyant 

and residual trapping types in the storage formation (SF). The 

SAU minimum depth limit of 3,000 feet (914 meters, or almost 1 

kilometer) ensures that carbon dioxide (CO2) is in a supercritical 

state to maximize the storage resource per unit volume. A depth of 

13,000 ft (3,962 m, or almost 4 km) is the lower limit accessible with 

average injection pressures and is the lower limit for a standard 

SAU. A deep SAU can be defined for depths greater than 13,000 ft 

(3,962 m) if favorable reservoir conditions exist. The lateral limit 

of the SAU is defined by the location where the top of the storage 

formation reaches the defined depth limit. Also shown are zones 

that may be excluded from an SAU because the regional seals are 

thin or because water in the storage formation is probably low in 

total dissolved solids (TDS less than 10,000 milligrams per liter). 

Modified from Brennan and others (2010) and Blondes, Brennan, 

and others (2013). 

Three basins (Central California Coast Basins; Columbia 

Basin of Oregon, Washington, and Idaho; and Raton Basin) 

contain only nonquantitative SAUs, bringing the total number of basins listed in table 3 and shown in figure 2 to 36. 

Because they lack resource estimates, these three basins are 

not included in table 2 or figure 3.

Areas of the Nation evaluated for CO2 storage potential 

are shown as “Evaluated areas” in figure 2, and the combined extents of the areas that were quantitatively assessed 

within each basin are shown as “Assessed areas.” USGS 

National Oil and Gas Assessment (NOGA) total petroleum 

system (TPS) boundaries (see http://energy.usgs.gov/OilGas/

AssessmentsData/NationalOilGasAssessment.aspx) were used 

as starting points for the evaluation of many specific basins. In 

some areas, the assessed storage reservoir continues beyond, 

or is smaller than, the TPS outline of that basin because SAU 

boundaries are defined differently than TPS boundaries. Additionally, some sedimentary basins were lumped into a composite-basin evaluation area because the SAUs are continuous 

throughout these areas (for example, the Hanna, Laramie, and 

Shirley Basins, fig. 2).

Buoyant and Residual Trapping

Two general storage types, buoyant and residual, were 

defined in the methodology used in this assessment (Brennan 

and others, 2010; Blondes, Brennan, and others, 2013). Carbon dioxide storage capacity was estimated for buoyant and 

residual storage traps that occur in sedimentary basins. For 

buoyant traps, CO2 can be held in place in porous formations 

by top and lateral seals. For residual traps, CO2 can be held 

in porous formations as individual droplets within pores by 

capillary forces (fig. 4). The residual storage resource consists 

of three injectivity classes based on reservoir permeability: 

residual trapping class 1 (R1SR) represents storage in rocks 

with permeability greater than 1 darcy (D); residual trapping 

class 2 (R2SR) represents storage in rocks with moderate permeability, defined as permeability between 1 millidarcy (mD) 

and 1 D; and residual trapping class 3 (R3SR) represents storage 

in rocks with low permeability, defined as permeability less 

than 1 mD.

Maximum buoyant trapping pore volume

Minimum buoyant trapping pore volume

Residual trapping pore volume

Regional seal

Storage formation

EXPLANATION

Storage Assessment Unit, Cross Section

Land surface

Probable low 

total dissolved 

solids zone Thin regional 

seal zone

Fault

3,000 ft to 13,000 ft

3,000 ft to 13,000 ft
Assessment Process 9

Assessment Categories

The six storage resource categories for the assessment are 

summarized below.

1. BSR, buoyant trapping storage resource: mass of CO2

that can be stored buoyantly beneath structural or stratigraphic traps with the potential to contain greater than 

500,000 barrels of oil equivalent (BOE).

2. R1SR, residual trapping class 1 storage resource: mass 

of CO2 that can be stored by residual trapping in rocks 

with permeability greater than 1 D.

3. R2SR, residual trapping class 2 storage resource: mass 

of CO2 that can be stored by residual trapping in rocks 

with permeability between 1 mD and 1 D.

4. R3SR, residual trapping class 3 storage resource: mass 

of CO2 that can be stored by residual trapping in rocks 

with permeability less than 1 mD.

5. TASR, technically accessible storage resource: total mass 

of CO2 that can be stored in the SAU.

6. KRRSR, known recovery replacement storage resource:

mass of CO2 that can be stored in existing hydrocarbon 

reservoirs. The KRRSR is a minimum range of values that 

represent the amount of CO2 at subsurface conditions 

that could replace the volume of known hydrocarbons in 

petroleum reservoirs. KRRSR is determined from production volumes rather than the geologic model of buoyant 

and residual resources that make up the TASR (Brennan 

and others, 2010; Blondes, Brennan, and others, 2013). 

The same type of resource is also included in the buoyant 

storage type estimated from a geologic model.

Data Sources

Several publicly available data sources and proprietary 

databases were used for this assessment. Lists of the data 

sources used in assessing SAUs in several basins are available 

in the basin-specific geologic framework publication series 

(Warwick and Corum, 2012). A general list of data sources 

used in the resource and allocation calculation processes 

is included in the companion assessment data publication 

(U.S. Geological Survey Geologic Carbon Dioxide Storage 

Resources Assessment Team, 2013a).

USGS National Oil and Gas Assessment publications 

were a significant source of reservoir characteristics and other 

geologic input parameters (see http://energy.usgs.gov/OilGas/

AssessmentsData/NationalOilGasAssessment.aspx). Datasharing agreements with numerous State geological surveys 

and universities (see “Acknowledgments” for the names of 

the organizations), many of which are members of the DOE 

National Energy Technology Laboratory (NETL) Regional 

Carbon Sequestration Partnerships, provided assessment 

geologists with reports, maps, and ancillary displays, as well 

as digital databases that were integral to the success of the 

project. In addition, peer-reviewed publications from the 

petroleum and carbon sequestration literature provided access 

to other interpretations and datasets.

Two principal proprietary petroleum databases were 

mined for a substantial proportion of the data used in the 

assessments; these are the “Significant Oil and Gas Fields 

of the United States Database” from Nehring Associates, 

Inc. (2010), and the databases of individual well information 

from IHS Inc. (2010, 2011a,b). Water-quality data from Breit 

(2002), Blondes and Gosai (2011), and the National Energy 

Technology Laboratory (NETL) Brine Database (Hovorka and 

others, 2000), amongst others, and other datasets available 

from State sources were used to determine the potential status 

of SAUs in regard to the EPA underground source of drinking 

water (USDW) regulations (U.S. Environmental Protection 

Agency, 2008, 2009, 2010).

Assessment Process

Assessment Assumptions and Constraints

Several assumptions were implemented to complete 

the assessment within the timeframe specified by the Energy 

Independence and Security Act (Public Law 110–140; U.S. 

Congress, 2007). The methodology of Brennan and others (2010) and Blondes, Brennan, and others (2013) does 

not factor in engineering issues such as injection rate or 

time-dependent variables to determine the storage potential 

of SAUs. Additionally, the methodology does not identify 

locations within individual SAUs where the storage resources 

would be most accessible or favorable. Also, the resources 

were estimated without consideration either of accessibility due to land-management or regulatory restrictions or of 

economic viability. Thus, if storage of CO2 within a formation 

is feasible with current technology, it was considered for this 

report. Because the legislation that mandated this assessment 

(Public Law 110–140) required that the assessment incorporate USDW regulations of the EPA (U.S Environmental 

Protection Agency, 2008, 2009, 2010), a substantial percentage of a potential storage formation containing water with 

less than 10,000 milligrams per liter (mg/L) of total dissolved 

solids (TDS) (considered freshwater for the purpose of this 

assessment) would be disqualified as a protected underground 

source of potential drinking water. As discussed in Blondes, 

Brennan, and others (2013), if a potential SAU contains both 

saline water and freshwater, the area of the SAU considered 

for the estimate was reduced to account for the estimated fraction of freshwater thought to be present. A potential exception 

may be granted by the EPA (or by States to whom the EPA 

has delegated responsibilities) for areas of current petroleum 

production with freshwater and for areas where waivers may 
10 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

be obtained for CO2 storage. These areas were considered 

for buoyant storage (Blondes, Brennan, and others, 2013). 

Additionally, all CO2 storage formations must be overlain by a 

low-permeability robust sealing formation having a minimum 

thickness of about 75 ft (23 m) depending on the seal lithology (Blondes, Brennan, and others, 2013). These constraints 

are illustrated in figure 4 and discussed further in Brennan and 

others (2010) and Blondes, Brennan, and others (2013). Federally owned offshore areas were not assessed because resource 

assessments in these areas are typically done by the Bureau of 

Ocean Energy Management (BOEM).

Besides the SAU depth constraints described by Brennan and others (2010), some additional assumptions were 

made to identify SFs technically feasible for geologic storage 

of CO2. One major assumption was that increases in pressure 

within the reservoir during CO2 injection could be mitigated 

by pressure management, for example by water production 

from the SF. Such pressure management should be used to 

avoid complications associated with reservoir or seal rock 

integrity, induced seismicity, or potential leakage from the 

storage formation. Therefore, failure of reservoir or seal rock 

integrity caused by injection site operations and the consequential potential for CO2

 leakage along faults and fractures, 

or by updip migration, were constraints not taken into account 

in this assessment.

Resource Calculations

The probabilistic methodology used in this assessment 

follows that described by Brennan and others (2010) and 

Blondes, Brennan, and others (2013). The calculation for 

the total technically accessible storage resource, TASR (see 

“Assessment Categories” section above), can be summarized 

with the following equation (Blondes, Brennan, and others, 

2013), which adds the buoyant trapping storage resource to the 

sum of the residual trapping storage resources:

TA B B A T B R Ri Ri SR CO PV SE

i

= + CO ( ) SF PI PI − PV W SE 

  =

ρ ρ ∑ φ 2 2

1

3

, (1)

where

• The buoyant trapping storage resource, BSR is equivalent to the first term on the right side of the equation 

(BSR = CO2

B B PV SE).

• Each of the three terms in the summation is a residual 

trapping storage resource output: R1SR, R2SR, or R3SR.

• CO2 is the density of CO2 and is determined from subsurface geothermal and pressure gradient data for each 

basin, from comparisons with analog basins, or from 

published gradients.

• BPV is the geologically determined pore volume that 

can store CO2 by buoyant trapping. It is estimated on 

the basis of hydrocarbon production, undiscovered 

resources, and volume calculations of geologic traps.

• BSE and RiSE are the buoyant and residual trapping storage efficiencies, respectively, defined as the fraction 

of accessible pore volume that will be occupied by 

injected CO2. These are determined from estimates of 

subsurface geothermal and pressure gradients, multiphase flow parameters, and fluid chemistry.

• ASF is the area of the storage formation within the SAU 

and is constrained by using structure maps or data at 

the relevant depth ranges for the storage formation.

• TPI is the thickness of the net porous interval and is 

generally calculated by using net thickness:gross thickness assumptions applied to the total SAU thickness.

•  PI is the porosity of the net porous interval, obtained 

from measurements of porosity in the interval or analog rock porosity data.

• RW is the area fraction of the SAU available for storage 

after consideration of EPA water-quality guidelines or 

highly fractured seals.

• i = 1, 2, or 3; the numbers refer to the names of the 

residual trapping injectivity classes.

• Ri can represent injectivity class fractions 1, 2, or 3, 

which are determined from a probabilistic distribution 

of rock permeability data.

Equation 1 sums the first five assessment results in the 

“Assessment Categories” section above. The sixth assessment 

result, KRRSR, is nongeologic and was calculated separately by 

using known recovery production volumes, buoyant trapping 

storage efficiency factors, and CO2 . To help define the input 

parameters for TASR and KRRSR, additional parameters were 

estimated by the assessment geologist or the assessment team. 

Formation volume factors (FVF) for oil, gas, and natural gas 

liquids were used to convert surface production volumes to 

equivalent volumes at depth. These were calculated from basin 

subsurface geothermal gradients and reservoir characteristics. The depth range was determined for each SAU and was 

important for the density, storage efficiency, and FVF calculations (Blondes, Brennan, and others, 2013).

During the assessment, the USGS geologist specified a 

minimum, most likely, and maximum estimate range about the 

mean of each input parameter. The three estimates for each 

parameter were used to define continuous distributions, such 

as a lognormal or a Beta-PERT distribution (Blondes, Brennan, and others, 2013). The calculation procedure is outlined 

in figure 5 and is described in detail in Blondes, Brennan, 

and others (2013). For simplicity, the storage formation 

pore volume (SFPV) at the top of figure 5 is equivalent to the 

A T SF PI PI term in equation 1, whereas all other equation 1 

variables are shown. Storage resources were calculated with 
Assessment Process 11

correctly propagated uncertainty (or propagation of error) by 

using a Monte Carlo method in which each input distribution 

was sampled 10,000 times. Assessment results for all SAUs 

include a mean, P5, P50 (median), and P95 for each of the six 

reported storage resource assessment categories (tables 1, 2, 

and 3). The terminology used in this report differs from that 

used by the petroleum industry and follows standard statistical practice (for example, Everitt and Skrondal, 2010) where 

a percentile represents the probability that the true storage 

resource is less than the value reported. For example, if the 

P95 for TASR is 1 Gt, there is a 95-percent probability that the 

true TASR value is less than 1 Gt. This is considered the high 

estimate.

An in-depth discussion and an explanation of the resource 

calculation methodology are in Blondes, Brennan, and others 

(2013). Input data for each SAU are contained in the companion assessment data publication (U.S. Geological Survey 

Geologic Carbon Dioxide Storage Resources Assessment 

Team, 2013a).

Aggregation

The calculated CO2 storage resources for each SAU are 

reported in the form of a probabilistic distribution, reported 

as the P5, P50, P95, and mean, although the modeling was done 

for the entire distribution. The assessment then combined 

the six resource results for an SAU (listed above) to basin, 

regional, and national scales using probabilistic aggregation 

to appropriately propagate uncertainty. Because USGS oil and 

Technically accessible 

storage resource 

(TASR)

(ρCO2

)

Technically accessible 

storage volume 

(TASV)

R3SR R2SR R1SR

(ρCO2)

R3SV R2SV R1SV

R3SE R2SE R1SE

R3PV R2PV R1PV

Injectivity classes 

allotment 

(R1, R2, R3)

Area fraction 

(RW)

Residual trapping 

pore volume 

(RPV)

Storage resource

Density (ρ)

Storage volume

Storage efficiency

Pore volume

Water-quality factor

Storage formation 

pore volume 

(SFPV)

Buoyant trapping 

storage resource 

(BSR)

(ρCO2

)

Buoyant trapping 

storage volume 

(BSV)

Buoyant trapping 

storage efficiency 

(BSE)

Buoyant trapping 

pore volume 

(BPV)

Known recovery replacement 

storage resource 

(KRRSR)

(ρCO2

)

Buoyant trapping 

storage efficiency 

(BSE)

Known recovery 

production volumes 

(KRRES)

Residual trapping 

resource calculation

Buoyant trapping 

resource calculation

Known recovery replacement 

resource calculation

Figure 5. Flow diagram of the key steps for calculating known 

recovery replacement storage resources (KRRSR), buoyant 

trapping storage resources (BSR), residual trapping storage 

resources (R1SR, R2SR, R3SR), and technically accessible storage 

resources (TASR). Residual trapping injectivity categories are 

represented as class 1 (R1), class 2 (R2), and class 3 (R3). 

Also included are steps for calculating water quality, storage 

efficiency, and carbon dioxide density ( CO2 ). Modified from 

Brennan and others (2010) and Blondes, Brennan, and others 

(2013).
12 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

gas resource assessments have shown that geologic dependencies exist between assessment units, the aggregation procedure required estimating the dependencies, or correlations, 

between individual units (Schuenemeyer and Gautier, 2010). 

This aggregation procedure, which incorporated estimates 

of correlation among all SAUs (see U.S. Geological Survey 

Geologic Carbon Dioxide Storage Resources Assessment 

Team, 2013a, table 2), was necessary for the rigorous estimation of resource percentile at the basin, regional, and national 

scales. All assessments were conducted by USGS employees 

for process consistency. The aggregation procedure used in 

this study is discussed in detail in Blondes, Schuenemeyer, and 

others (2013).

Results of the Assessment of 

Technically Accessible Storage 

Resources

The results for the six CO2 storage resource categories 

are summarized below and illustrated in tables 1–3. Table 

1 summarizes the national results, and table 2 contains the 

assessment results aggregated by region and basin. Table 3 

presents the results by basin and individual SAU. Most results 

are rounded to two significant figures.

Brennan and others (2010) suggested that existing 

technology, or that which is based on present-day geoscience 

knowledge and existing engineering capabilities, would be 

used to store CO2; estimates made on that basis indicate that 

the technically accessible storage resource (TASR) beneath U.S. 

onshore areas and State waters ranges from approximately 

2,300 Gt at the P5 percentile to as much as 3,700 Gt at the P95

percentile, with a mean of 3,000 Gt (table 1). The estimated 

range of uncertainty about the mean for the TASR is illustrated 

in figure 6. A complete set of results for each SAU, along 

with plots of the empirical cumulative distribution functions 

(CDFs) for each SAU, is available in the companion data 

report (U.S. Geological Survey Geologic Carbon Dioxide 

Storage Resources Assessment Team, 2013a). The TASR was 

estimated for eight regions of the United States (figs. 1B and 

2). The Coastal Plains Region accounts for 65 percent of the 

TASR (fig. 1B), and its U.S. Gulf Coast area accounts for the 

majority of the resources (59 percent). The Alaska, Rocky 

Mountains and Northern Great Plains, and Eastern Mid-Continent Regions contain the next largest storage resources, with 

each containing 9, 9, and 8 percent of the total, respectively. 

All other regions contain 5 percent or less of the total storage 

resources. The distributions of the TASR for regions with multiple basins are illustrated in figure 7A–F. The Pacific Northwest 

Region and Eastern Mesozoic Rift Basins Region contain only 

one assessment unit each, and so a distribution illustration is 

not presented for these regions.

Buoyant Trapping Storage

The mean technically accessible storage resource available for buoyant trapping storage of CO2

 in the United States 

is equivalent to approximately 44 Gt (P5 = 19 Gt, and P95 = 

110 Gt) of CO2 (tables 1–3, figs. 1A and 8A). The national 

buoyant storage resource constitutes approximately 2 percent 

of the TASR (fig. 1A). The assessment regions that contain significant buoyant storage resources include the Coastal Plains 

(primarily U.S. Gulf Coast), Alaska, Western Mid-Continent, 

and Rocky Mountains and Northern Great Plains (fig. 8A).

Residual Trapping Storage

The mean estimated storage capacities for the three 

residual trapping storage classes are summarized here: residual 

trapping class 1 has 140 Gt (P5 = 97 Gt, and P95 = 200 Gt), 

or approximately 5 percent of the mean TASR; residual trapping class 2 has 2,700 Gt (P5

 = 2,100 Gt, and P95 = 3,300 Gt), 

or approximately 89 percent of the mean TASR; and residual 

trapping class 3 has 130 Gt (P5 = 58 Gt, and P95 = 230 Gt), 

or approximately 4 percent of the mean TASR (table 1; fig 

1A). Residual trapping class 2 contains the most significant 

resources of the three residual storage classes and of the TASR

(fig. 1A). The regional distribution of residual trapping class 2 

storage resources is illustrated in figure 8B, with the primary 

regions being the Coastal Plains (especially the U.S. Gulf 

Coast area), Alaska, Eastern Mid-Continent, and Rocky Mountains and Northern Great Plains.

Petroleum Reservoirs

Known hydrocarbon recovery volumes indicate that the 

CO2 storage resources (KRRSR) available in petroleum reservoirs within the assessed areas range from approximately 11 

Gt at the P5 probability percentile to as much as 15 Gt at the 

P95 probability percentile, with a mean of 13 Gt. This value 

indicates that approximately 30 percent of the mean buoyant 

storage resources reported above is in petroleum reservoirs.

Discussion of Results

The numerical results of the assessment reveal important 

aspects of the distribution of potential CO2 storage resources 

in the United States. The following list has some of the key 

findings of this assessment.

1. Most (89 percent) of the TASR is in the residual trapping 

class 2 storage resource category (mean estimate of 2,700 

Gt; fig. 1A). Residual trapping classes 1 and 3 account for 

5 and 4 percent of the TASR, respectively (fig. 1A). These 

resources occur in all assessed basins and need to be better defined by site characterization studies prior to their 

utilization for CO2 storage.
Discussion of Results 13

Figure 6. Graphs showing empirical cumulative distribution function 

(CDF) plots of all six categories of technically accessible storage 

resources (TASR) for carbon dioxide in the United States, exclusive 

of federally owned offshore areas. The cumulative probability for 

a given percentile represents the probability that the true storage 

resource is less than the value shown. All values are rounded to two 

significant figures. Data are listed in table 1 and are given in billions 

of metric tons (gigatons, Gt). Where the mean and P50 values are the 

same within rounding to two significant figures, their respective dots 

on the curve may be slightly offset and reflect the unrounded values.

100 200 300 400

0.0

0.2

0.4

0.6

0.8

1.0

Residual trapping class 3 storage resource (Gt)

Cumulative probability

●

●

●

●

P5 = 58

P50 = 120

Mean = 130

P95 = 230

10 12 14 16 18

0.0

0.2

0.4

0.6

0.8

1.0

Known recovery replacement storage resource (Gt)

Cumulative probability

●

●

●

●

P5 = 11

P50 = 13

Mean = 13

P95 = 15

1,500 2,000 2,500 3,000 3,500 4,000 4,500

0.0

0.2

0.4

0.6

0.8

1.0

Residual trapping class 2 storage resource (Gt)

Cumulative probability

●

●

●

●

P5 = 2,100

P50 = 2,600

Mean = 2,700

P95 = 3,300

100 200 300 400 500 600

0.0

0.2

0.4

0.6

0.8

1.0

Buoyant trapping storage resource (Gt)

Cumulative probability

●

●

●

●

P5 = 19

P50 = 31

Mean = 44

P95 = 110

200 400 600 800

0.0

0.2

0.4

0.6

0.8

1.0

Residual trapping class 1 storage resource (Gt)

Cumulative probability

●

●

●

●

P5 = 97

P50 = 140

Mean = 140

P95 = 200

2,000 3,000 4,000 5,000

0.0

0.2

0.4

0.6

0.8

1.0

Technically accessible storage resource (Gt)

Cumulative probability

●

●

●

●

P5 = 2,300

P50 = 3,000

Mean = 3,000

P95 = 3,700
14 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Kandik Basin

(1.5 Gt)

1%

Alaska North Slope

(270 Gt)

99%

F. Alaska Region, TASR = 270 Gt

U.S. Gulf Coast

(1,800 Gt)

91%

South Florida Basin

(170 Gt)

8%

Atlantic Coastal Plain

(14 Gt)

1%

E. Coastal Plains Region, TASR = 1,900 Gt

Michigan Basin

(57 Gt)

25%

Appalachian

Basin

(20 Gt)

9%

Black Warrior

Basin

(0.31 Gt)

<1%

Illinois Basin

(150 Gt)

66%

D. Eastern Mid-Continent Region, TASR = 230 Gt

Arkoma Basin

(7.9 Gt)

5%

Bend Arch and

Fort Worth Basin

(15 Gt)

10% 

Kansas Basins

(0.32 Gt)

<1%

Palo Duro Basin

(7.2 Gt)

5%

Permian Basin

(59 Gt)

39%

Anadarko and 

Southern Oklahoma

Basins

(62 Gt)

41%

C. Western Mid-Continent Region, TASR = 150 Gt

Denver Basin

(3.7 Gt)

1%

Wind River Basin

(8.1 Gt)

3%

Wyoming-Idaho-Utah Thrust Belt

(44 Gt)

16%

Eastern Great

Basin

(0.23 Gt)

<1%

Bighorn Basin

(1.8 Gt)

1%

Williston Basin

(150 Gt)

54%

Greater Green

River Basin

(39 Gt)

15% 

Hanna, Laramie,

and

Shirley Basins

(2.3 Gt)

1%

Paradox Basin (3.4 Gt)

1%

Powder River Basin (18 Gt)

7%

San Juan Basin

(0.74 Gt)

<1%

Uinta and Piceance Basins

(3.8 Gt)

1% 

B. Rocky Mountains and Northern Great Plains Region, TASR = 270 Gt

Ventura Basin

(6.0 Gt)

7% Los Angeles Basin

(3.7 Gt)

4%

Sacramento Basin

(29 Gt)

33%

San Joaquin Basin (51 Gt)

56%

A. California Region, TASR = 90 Gt
Discussion of Results 15

2. The 44 Gt (mean estimate) of buoyant trapping storage 

resources includes non-hydrocarbon-bearing reservoir 

formations, but most of the resources are well defined by 

hydrocarbon exploration data. Existing oil in hydrocarbon 

reservoirs may be produced in the near future by using 

enhanced-oil-recovery technology that utilizes anthropogenic CO2

, and then the reservoirs could be used for 

CO2 storage. Because of the depth of knowledge about 

the hydrocarbon reservoirs, buoyant trapping storage 

resources in these reservoirs may be more attractive for 

storage of CO2 than residual trapping storage resources.

3. The regions with the largest technically accessible storage resources (fig. 7A–F) are the Coastal Plains Region 

(mean estimate of 1,900 Gt, of which about 1,800 Gt, 

or 91 percent, is in the U.S. Gulf Coast) and the Alaska 

Region (mean estimate of 270 Gt), where the resource is 

almost entirely in the Alaska North Slope (tables 2 and 3). 

Storage resources in the U.S. Gulf Coast are near major 

population centers and industrial CO2 sources and will 

likely be utilized for CO2 storage in subsurface formations 

in the near future. The CO2 storage resources in Alaska 

are in remote areas in the northern part of the State and 

may not be readily utilized for anthropogenic CO2 storage. However, the Alaska North Slope petroleum industry 

may utilize these subsurface reservoirs for storage of CO2

that is coproduced with hydrocarbons or stored during the 

enhanced-oil-recovery process using CO2.

4. Available water-quality databases indicate that many 

basins in the Western United States contain variable 

amounts of freshwater (<10,000 mg/L TDS), which, 

according to EPA regulations incorporated in the Energy 

Independence and Security Act of 2007, will restrict the 

use of the CO2 storage resource capacity in these basins. 

Among the basins in the Rocky Mountains and Northern 

Great Plains Region (fig. 2), the Williston Basin, which 

contains predominantly saline water, has the most available storage resource (mean estimate of 150 Gt; fig. 7B). 

Please refer to Blondes, Brennan, and others (2013) and 

U.S. Geological Survey Geologic Carbon Dioxide Storage Resources Assessment Team (2013a) for a detailed 

accounting of how water quality affected the delineation 

of the SAU areas within individual basins.

5. Forty-six deep SAUs (at depths greater than 13,000 ft; 

3,962 m) in 13 basins were quantitatively assessed (tables 

3 and 4). The deep SAUs account for 470 Gt, or 16 percent of the total TASR. In addition, deep SAUs account for 

6 percent of the total BSR. Any potential developer of the 

deep SAUs has to consider the increased operational pressures needed to inject CO2

 at depths greater than 13,000 ft 

(3,962 m).

6. Of the 10 SAUs having the largest storage capacity (table 

3), 8 are near population centers and may be utilized for 

geologic storage of anthropogenic CO2; the two exceptions are in the Alaska North Slope and the Williston 

Basin. These 10 SAUs, ranked in decreasing order of 

mean estimates of TASR, are listed below:

1. Sligo and Hosston Formations and Cotton Valley 

Group (610 Gt), U.S. Gulf Coast

2. Sligo and Hosston Formations and Cotton Valley 

Group Deep (220 Gt), U.S. Gulf Coast

3. Carrizo Sand and Wilcox Group (220 Gt), U.S. 

Gulf Coast

4. Frio and Vicksburg Formations (170 Gt), U.S. 

Gulf Coast

5. Lower Torok Formation (140 Gt), Alaska North 

Slope

6. Pre-Punta Gorda (110 Gt), South Florida Basin

7. Mount Simon Sandstone (94 Gt), Illinois Basin

8. Tuscaloosa and Woodbine Formations (85 Gt), 

U.S. Gulf Coast

9. Yegua and Cockfield Formations (62 Gt), U.S. 

Gulf Coast

10. Winnipegosis Formation, Interlake Formation, 

and Bighorn Group (61 Gt), Williston Basin

7. The total geologic storage resources for CO2 in the United 

States are large, and both types will probably be needed. 

The U.S. Energy Information Administration (2012b) 

estimated that the 2011 national energy-related CO2 emissions were 5.5 Gt. The mean estimate by the USGS of the 

technically accessible geologic storage resource (TASR) for 

CO2 in the United States is 3,000 Gt, which is more than 

500 times the annual energy-related CO2 emissions. However, the mean buoyant trapping storage resource (BSR) 

of 44 Gt is approximately eight times the annual energyrelated CO2

 emissions. The BSR estimate indicates that the 

use of residual trapping storage resources for CO2 will be 

required to significantly reduce anthropogenic CO2 emissions into the atmosphere during the next few decades.

Figure 7 (facing page). Pie charts showing mean estimates 

of technically accessible storage resources (TASR) for carbon 

dioxide (CO2) in selected regions of the United States. Resources 

in federally owned offshore areas were not assessed. Resource 

estimates are illustrated for six of the eight regions shown in 

figure 2: A, California Region; B, Rocky Mountains and Northern 

Great Plains Region; C, Western Mid-Continent Region; D, Eastern 

Mid-Continent Region; E, Coastal Plains Region; and F, Alaska 

Region. The Pacific Northwest Region and Eastern Mesozoic Rift 

Basins Region contain only one quantitatively assessed storage 

assessment unit each and are therefore not presented in this 

figure. Mean values sum to totals but are reported to only two 

significant figures. Gt, gigatons.
16 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Figure 8. Pie charts showing 

mean estimates of (A) buoyant 

trapping storage resources and 

(B) residual trapping class 2 

storage resources for carbon 

dioxide (CO2) in the United 

States, by region. Resources in 

federally owned offshore areas 

were not assessed. Mean 

values sum to totals but are 

reported to only two significant 

figures. Gt, gigatons.

Coastal Plains

(1,800 Gt)

66%

Alaska

(210 Gt)

8%

Pacific Northwest

(12 Gt)

<1% California

(86 Gt)

3%

Western Mid-Continent

(130 Gt)

5%

Eastern Mesozoic Rift Basins

(0.29 Gt)

<1% 

Rocky Mountains and

Northern Great Plains

(240 Gt)

9%

Eastern Mid-Continent

(210 Gt)

8%

B. Residual trapping class 2 storage resource by region, total = 2,700 Gt

Pacific Northwest

(<0.01 Gt)

<1%

California

(0.52 Gt)

1%

Western

Mid-Continent

(4.5 Gt)

11%

Eastern Mesozoic Rift Basins

(<0.01 Gt)

<1% 

Rocky Mountains and

Northern Great Plains

(3.2 Gt)

7%

Eastern Mid-Continent

(0.94 Gt)

2%

Coastal Plains

(17 Gt)

38%

Alaska

(18 Gt)

41%

A. Buoyant trapping storage resource by region, total = 44 Gt
Conclusions 17

Comparison of Results with Findings 

from Previous Assessments

These USGS basin-scale assessment results are comparable with findings from other assessments of geologic CO2

 storage capacities of the United States and North America. Most 

notable are the DOE NETL Regional Carbon Sequestration 

Partnerships assessments and carbon sequestration atlases of 

the U.S. Department of Energy, National Energy Technology 

Laboratory (2008, 2010, 2012) and the North American Carbon Atlas Partnership (2012). For a review of the USGS, DOE 

NETL, and other CO2 storage assessment methodologies, see 

Spencer and others (2011), Popova and others (2012), Prelicz 

and others (2012), and U.S. Department of Energy, National 

Energy Technology Laboratory (2012). The USGS assessment 

methodology (Brennan and others, 2010; Blondes, Brennan, 

and others, 2013) and assessment results are unique among 

the various assessments mentioned above, because the USGS 

methodology is fully probabilistic and better accounts for the 

range of uncertainties found in geologic settings. Another key 

difference between the USGS and previous assessments is that 

the USGS assessment reports resources for individual SAUs 

located within defined basins of the United States. In addition, 

unlike the other assessments, the USGS only assessed buoyant traps that meet the minimum depth criteria of 3,000 ft (914 

m) and that have an overlying regional seal as described in 

Brennan and others (2010) and Blondes, Brennan, and others 

(2013). Also, the USGS assessment results are statistically 

aggregated at the basin, region, and national scales. Results 

reported by the previous U.S. Department of Energy, National 

Energy Technology Laboratory (2008, 2010, 2012) assessments are regional and include regional results from areas 

within Canada. The North American Carbon Atlas Partnership 

(2012) reports CO2 storage resources for Canada, Mexico, and 

the United States. Although the USGS and DOE NETL assessment methodologies and implementations are different, both 

USGS and DOE assessment efforts have identified geologic 

storage resources on the order of thousands of gigatons of CO2

within the United States.

Conclusions

The U.S. Geological Survey recently completed an 

evaluation of the TASR for CO2 for 36 sedimentary basins in the 

onshore areas and State waters of the United States. The TASR

is an estimate of the geologic storage resource that may be 

available for CO2 injection and storage and is based on current 

geologic and hydrologic knowledge of the subsurface and current engineering practices. Following the assessment methodology of Brennan and others (2010) and Blondes, Brennan, 

and others (2013), the assessment team members obtained a 

mean estimate of approximately 3,000 gigatons (Gt) of subsurface CO2

 storage capacity that is technically accessible in 

onshore areas and State waters; this amount is more than 500 

times the 2011 annual U.S. energy-related CO2 emissions of 

5.5 Gt (U.S. Energy Information Administration, 2012b).

Table 4. Mean estimates by the U.S. Geological Survey in 2012 for technically accessible storage 

resources (TASR) for carbon dioxide (CO2) in deep storage assessment units (SAUs) in the United 

States.

[Estimates are in millions of metric tons (megatons, Mt). Mean values sum to totals but are reported to only two significant figures. Deep SAUs are at depths greater than 13,000 feet (3,962 meters). The 46 deep SAUs are in 13 basins]

Basin name

TASR

in deep SAUs 

(Mt)

Percent of 

basin TASR

Percent of 

national TASR

Alaska North Slope 56,000 21 2

Anadarko and Southern Oklahoma Basins 25,000 40 1

Bighorn Basin 350 20 0

Greater Green River Basin 20,000 52 1

Hanna, Laramie, and Shirley Basins 730 32 0

Los Angeles Basin 740 20 0

Permian Basin 19,000 31 1

San Joaquin Basin 1,400 3 0

Uinta and Piceance Basins 710 19 0

U.S. Gulf Coast 310,000 18 11

Williston Basin 11,000 7 0

Wind River Basin 1,400 17 0

Wyoming-Idaho-Utah Thrust Belt 24,000 54 1

Total 470,000 16
18 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

The estimate of the TASR includes buoyant trapping storage and three classes of residual trapping storage. Buoyant 

trapping storage of CO2 can occur in structural or stratigraphic 

closures, for which the USGS team obtained a mean estimate 

of 44 Gt of storage; that amount is approximately eight times 

the annual energy-related CO2 emissions that were estimated 

by the U.S. Energy Information Administration (2012b), and 

this assessment indicates that the use of residual trapping storage resources for CO2

 will be required to significantly reduce 

anthropogenic CO2 emissions into the atmosphere during the 

next few decades. Known hydrocarbon recovery volumes 

indicate that the CO2 storage resources (KRRSR) available in 

petroleum reservoirs within the assessed areas range from 

approximately 11 Gt at the P5 probability percentile to as much 

as 15 Gt at the P95 probability percentile, with a mean of 13 Gt. 

For CO2 that is held in place by capillary pore pressures (residual trapping) in areas outside of buoyant traps, three injectivity 

classes were defined on the basis of reservoir permeability. 

These classes include (1) residual trapping class 1 for rocks 

with very high permeability, defined as permeability greater 

than 1 D; (2) residual trapping class 2 for rocks with moderate permeability, defined as permeability between 1 mD and 1 

D; and (3) residual trapping class 3 for the remainder of rocks 

in the storage formation that have low permeability, defined 

as permeability less than 1 mD. The mean estimated storage 

capacities for the three residual storage classes follow: residual 

trapping class 1 has 140 Gt; residual trapping class 2 has 2,700 

Gt; and residual trapping class 3 has 130 Gt.

References Cited

Blondes, M.S., Brennan, S.T., Merrill, M.D., Buursink, M.L., 

Warwick, P.D., Cahan, S.M., Cook, T.A., Corum, M.D., 

Craddock, W.H., DeVera, C.A., Drake, R.M., II, Drew, L.J., 

Freeman, P.A., Lohr, C.D., Olea, R.A., Roberts-Ashby, T.L., 

Slucher, E.R., and Varela, B.A., 2013, National assessment 

of geologic carbon dioxide storage resources—Methodology implementation: U.S. Geological Survey Open-File 

Report 2013–1055, 26 p., accessed May 10, 2013, at 

http://pubs.usgs.gov/of/2013/1055/.

Blondes, M.S., and Gosai, M.A., 2011, An expanded Wyoming water quality database [abs.]: American Association of Petroleum Geologists Rocky Mountain Section, 

Annual Meeting, Cheyenne, Wyo., June 25–29, 2011, 

Abstracts, 1 p., accessed March 10, 2013, at http://www.

searchanddiscovery.com/abstracts/pdf/2011/rocky/abstracts/

ndx_blondes.pdf.

Blondes, M.S., Schuenemeyer, J.H., Olea, R.A., and Drew, 

L.J., 2013, Aggregation of carbon dioxide sequestration storage assessment units: Stochastic Environmental 

Research and Risk Assessment, DOI:10.1007/s00477-

013-0718-x, 21 p., accessed May 31, 2013, at http://link.

springer.com/article/10.1007%2Fs00477-013-0718-x.

Breit, G.N., comp., 2002, Produced waters database: U.S. 

Geological Survey database, accessed November 8, 2012, at 

http://energy.cr.usgs.gov/prov/prodwat/.

Brennan, S.T., Burruss, R.C., Merrill, M.D., Freeman, P.A., 

and Ruppert, L.F., 2010, A probabilistic assessment methodology for the evaluation of geologic carbon dioxide storage: 

U.S. Geological Survey Open-File Report 2010–1127, 31 

p., accessed September 19, 2012, at http://pubs.usgs.gov/

of/2010/1127.

Burruss, R.C., Brennan, S.T., Freeman, P.A., Merrill, M.D., 

Ruppert, L.F., Becker, M.F., Herkelrath, W.N., Kharaka, 

Y.K., Neuzil, C.E., Swanson, S.M., Cook, T.A., Klett, T.R., 

Nelson, P.H., and Schenk, C.J., 2009, Development of a 

probabilistic assessment methodology for evaluation of 

carbon dioxide storage: U.S. Geological Survey Open-File 

Report 2009–1035, 81 p., accessed September 19, 2012, at 

http://pubs.usgs.gov/of/2009/1035/.

Everitt, B.S., and Skrondal, Anders, 2010, The Cambridge 

dictionary of statistics (4th ed.): Cambridge, England, Cambridge University Press, 478 p.

Hovorka, S.D., Romero, M.L., Treviño, R.H., Warne, A.G., 

Ambrose, W.A., Knox, P.R., and Tremblay, T.A., 2000, 

Project evaluation, Phase II; Optimal geological environments for carbon dioxide disposal in brine-bearing formations (aquifers) in the United States: The University of 

Texas at Austin, Bureau of Economic Geology, final report 

prepared for U.S. Department of Energy, National Energy 

Technology Laboratory, under contract no. DE–AC26–

98FT40417, 232 p. (GCCC [Gulf Coast Carbon Center] 

Digital Publication Series 00–01, available at http://www.

beg.utexas.edu/gccc/bookshelf/Final%20Papers/00-01-

Final.pdf.)

IHS Inc., 2010, PIDM [Petroleum Information Data Model] 

relational U.S. well data [data current as of December 23, 

2009]: Englewood, Colo., IHS Inc., database.

IHS Inc., 2011a, Enerdeq U.S. well data: Englewood, Colo., 

IHS Inc., database, accessed January 20–26, 2011, at http://

energy.ihs.com/.

IHS Inc., 2011b, IHS interpreted formation tops and online 

structure maps [data current as of 2011]: Englewood, Colo., 

IHS Inc., database.

Intergovernmental Panel on Climate Change, 2001, Climate 

change 2001—The scientific basis, Contribution of Working 

Group I to the third assessment report of the Intergovernmental Panel on Climate Change (Houghton, J.T., Ding, 

Y., Griggs, D.J., Noguer, M., van der Linden, P.J., Dai, X., 
References Cited 19

Maskell, K., and Johnson, C.A., eds.): Cambridge, U.K., 

Cambridge University Press, 881 p., accessed February 25, 

2013, at http://www.grida.no/publications/other/ipcc_tar/.

Jarvis, A., Reuter, H.I., Nelson, Andrew, and Guevara, 

Edward, 2008, Hole-filled SRTM [Shuttle Radar Topographic Mission] for the globe, version 4: available from 

the CGIAR [Consultative Group for International Agricultural Research]-Consortium for Spatial Information SRTM 

90m Database; accessed January 15, 2012, at http://www.

cgiar-csi.org/data/srtm-90m-digital-elevation-database-v4-

1#acknowledgements.

Jones, K.B., Corum, M.D., and Blondes, M.S., 2012, USGS 

workshop on CO2 sequestration in unconventional reservoirs: Greenhouse News, no. 106, June 2012, p. 16–18, 

accessed December 7, 2012, at http://www.ieaghg.org/

index.php?/Greenhouse-News/.

Klett, T.R., Schmoker, J.W., Charpentier, R.R., Ahlbrandt, 

T.S., and Ulmishek, G.F., 2005, Glossary, chap. 25 of

U.S. Geological Survey Southwestern Wyoming Province 

Assessment Team, Petroleum systems and geologic assessment of oil and gas in the Southwestern Wyoming Province, 

Wyoming, Colorado, and Utah: U.S. Geological Survey 

Digital Data Series DDS–69–D, 3 p., on CD–ROM. (Also 

available at http://pubs.usgs.gov/dds/dds-069/dds-069-d/.)

Lemmon, E.W., McLinden, M.O., and Friend, D.G., 2009, 

Thermophysical properties of fluid systems, in Linstrom, 

P.J., and Mallard, W.G., eds., NIST chemistry WebBook: 

National Institute of Standards and Technology (NIST) 

Standard Reference Database Number 69, accessed December 10, 2012, at http://webbook.nist.gov/chemistry.

MacMinn, C.W., Szulczewski, M.L., and Juanes, Ruben, 2010, 

CO2 migration in saline aquifers. Part 1, Capillary trapping under slope and groundwater flow: Journal of Fluid 

Mechanics, v. 662, p. 329–351.

Nehring Associates, Inc., 2010, Significant oil and gas fields 

of the United States database [data current as of December 

2008]: Colorado Springs, Colo., Nehring Associates, Inc.

North American Carbon Atlas Partnership, 2012, The North 

American carbon storage atlas (1st ed.): U.S. Department 

of Energy, National Energy Technology Laboratory, 52 p., 

accessed November 6, 2012, at http://www.netl.doe.gov/

technologies/carbon_seq/refshelf/NACSA2012.pdf.

Popova, O.H., Small, M.J., McCoy, S.T., Thomas, A.C., 

Karimi, Bobak, Goodman, Angela, and Carter, K.M., 2012, 

Comparative analysis of carbon dioxide storage resource 

assessment methodologies: Environmental Geosciences, v. 

19, no. 3 p. 105–124, DOI:10.1306/eg.06011212002.

Prelicz, R.M., Mackie, E.A.V., and Otto, C.J., 2012, Methodologies for CO2

 storage capacity estimation—Review and 

evaluation of CO2 storage atlases: First Break, v. 30, no. 2, 

p. 71–76.

Schlumberger, 2011, Injectivity test, [entry] in Schlumberger 

oilfield glossary: Schlumberger Web site, accessed December 20, 2012, at http://www.glossary.oilfield.slb.com/

Display.cfm?Term=injectivity%20test.

Schmoker, J.W., and Klett, T.R., 2005, U.S. Geological Survey 

assessment concepts for conventional petroleum accumulations, chap. 19 of U.S. Geological Survey Southwestern 

Wyoming Province Assessment Team, Petroleum systems 

and geologic assessment of oil and gas in the Southwestern 

Wyoming Province, Wyoming, Colorado, and Utah: U.S. 

Geological Survey Digital Data Series, DDS–69–D, 6 p., 

accessed February 20, 2013, at http://pubs.usgs.gov/dds/

dds-069/dds-069-d/REPORTS/69_D_CH_19.pdf.

Schuenemeyer, J.H., and Gautier, D.L., 2010, Aggregation 

methodology for the Circum-Arctic Resource Appraisal: 

Mathematical Geosciences, v. 42, no. 5, p. 583–594, 

DOI:10.1007/s11004-010-9274-9.

Spencer, L.K., Bradshaw, John, Bradshaw, B.E., Lahtinen, 

A.-L., and Chirinos, Alfredo, 2011, Regional storage capacity estimates—Prospectivity not statistics: Energy Procedia, 

v. 4, p. 4857–4864, DOI:10.1016/j.egypro.2011.02.453.

Thormahlen, L.F., 1999, Boundary development on the outer 

continental shelf: Minerals Management Service Mapping 

and Boundary Branch, OCS report MMS 99–0006, 12 p., 

accessed February 21, 2013, at http://www.boem.gov/BOEMNewsroom/Library/Publications/1999/99-0006-pdf.aspx.

U.S. Congress, 2007, Energy Independence and Security Act 

of 2007—Public Law 110–140: U.S. Government Printing Office, 311 p., accessed October 30, 2012, at http://

frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=110_

cong_public_laws&docid=f:publ140.110.pdf.

U.S. Department of Energy, National Energy Technology 

Laboratory, 2008, Carbon sequestration atlas of the United 

States and Canada (2d ed.; Atlas II): 142 p. (No longer 

accessible; see http://www.netl.doe.gov/technologies/

carbon_seq/refshelf/atlasII/.) (Superseded by U.S. Department of Energy, National Energy Technology Laboratory, 

2010 and 2012, cited below.)

U.S. Department of Energy, National Energy Technology 

Laboratory, 2010, Carbon sequestration atlas of the United 

States and Canada (3d ed.; Atlas III): 162 p., accessed 

April 21, 2011, at http://www.netl.doe.gov/technologies/

carbon_seq/refshelf//atlasIII/. (On January 16, 2013, Atlas 

III was at http://www.netl.doe.gov/technologies/carbon_seq/

refshelf/refshelf.html.) (Superseded by U.S. Department 
20 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

of Energy, National Energy Technology Laboratory, 2012, 

cited below.)

U.S. Department of Energy, National Energy Technology Laboratory, 2012, The United States 2012 carbon utilization and 

storage atlas (4th ed.; Atlas IV) (DOE/NETL-2012/1589): 

130 p., accessed December 20, 2012, at http://www.netl.doe.

gov/technologies/carbon_seq/refshelf/atlasIV/index.html.

U.S. Energy Information Administration, 2012a, Annual 

energy outlook 2012 with projections to 2035: U.S. Energy 

Information Administration [Report] DOE/EIA-0383(2012), 

239 p., accessed September 10, 2012, at http://www.eia.gov/

forecasts/aeo/pdf/0383(2012).pdf.

U.S. Energy Information Administration, 2012b, U.S. energyrelated carbon dioxide emissions, 2011: U.S. Energy 

Information Administration Web site, accessed December 

20, 2012, at http://www.eia.gov/environment/emissions/

carbon/.

U.S. Environmental Protection Agency, 2008, Federal requirements under the underground injection control (UIC) 

program for carbon dioxide (CO2) geologic sequestration 

(GS) wells: Washington, D.C., U.S. Environmental Protection Agency, proposed rule, accessed January 14, 2009, 

at http://www.epa.gov/fedrgstr/EPA-WATER/2008/July/

Day-25/w16626.htm.

U.S. Environmental Protection Agency, 2009, Safe Drinking 

Water Act (SDWA): Washington, D.C., U.S. Environmental 

Protection Agency Web site, accessed October 15, 2012, at 

http://www.epa.gov/ogwdw/sdwa/index.html.

U.S. Environmental Protection Agency, 2010, Final rule for 

Federal requirements under the underground injection 

control (UIC) program for carbon dioxide (CO2) geologic 

sequestration (GS) wells): Washington, D.C., U.S. Environmental Protection Agency Web site, accessed October 15, 

2012, at http://water.epa.gov/type/groundwater/uic/class6/

gsregulations.cfm.

U.S. Environmental Protection Agency, 2013, Causes of 

climate change: Washington, D.C., U.S. Environmental 

Protection Agency Web site, accessed February 22, 2013, at 

http://www.epa.gov/climatechange/science/causes.html.

U.S. Geological Survey Geologic Carbon Dioxide Storage 

Resources Assessment Team, 2013a, National assessment of 

geologic carbon dioxide storage resources—Data (ver. 1.1, 

September 2013): U.S. Geological Survey Data Series 774, 

13 p., plus 2 appendixes and 2 large tables in separate files, 

http://pubs.usgs.gov/ds/774/. (Supersedes ver. 1.0 released 

June 26, 2013.)

U.S. Geological Survey Geologic Carbon Dioxide Storage 

Resources Assessment Team, 2013b, National assessment 

of geologic carbon dioxide storage resources—Summary 

(ver. 1.1, September 2013): U.S. Geological Survey Fact 

Sheet 2013–3020, 6 p., http://pubs.usgs.gov/fs/2013/3020/. 

(Supersedes ver. 1.0 released June 26, 2013.)

Warwick, P.D., and Corum, M.D., eds., 2012, Geologic framework for the national assessment of carbon dioxide storage resources: U.S. Geological Survey Open-File Report 

2012–1024, accessed February 21, 2013, at http://pubs.usgs.

gov/of/2012/1024/. (Chapters A–C were posted by November 1, 2012.)
Glossary 21

The following definitions are modified from Brennan and 

others (2010) and other sources indicated.

barrels of oil equivalent (BOE) A unit of petroleum volume in which the gas part is expressed in terms of its energy 

equivalent in barrels of oil. For this assessment, the energy 

equivalent (not the volume equivalent) of 6,000 cubic feet of 

natural gas equals 1 barrel of oil equivalent (Klett and others, 

2005).

buoyancy Upward force on one phase (for example, a fluid) 

produced by the surrounding fluid (for example, a liquid or a 

gas) in which it is fully or partially immersed, caused by differences in density.

buoyant trapping A trapping mechanism by which CO2 is 

held in place by a top and lateral seal (either a sealing formation or a sealing fault), creating a column of CO2

 in communication across pore space.

buoyant trapping pore volume (BPV) A geologically determined, probabilistic distribution of the volume fraction of the 

storage formation (SF) that can store CO2 by buoyant trapping. 

This distribution minimum is typically defined by existing plus 

forecast undiscovered oil and gas production volumes. The 

maximum is probabilistically calculated from distributions of 

geologic parameters describing the known trapping structures 

within the storage formation.

buoyant trapping storage efficiency (BSE) A distribution of 

efficiency values that describe the fraction of buoyant trapping 

that can occur within a volume of porous media. The values 

used in the methodology for this assessment (0.2 min, 0.3 

most likely, and 0.4 max) are discussed in Blondes, Brennan, 

and others (2013).

buoyant trapping storage resource (BSR) The mass of CO2

retained in the storage formation by buoyant trapping.

buoyant trapping storage volume (BSV) The volume of CO2

retained in the storage formation by buoyant trapping.

carbon sequestration Both natural and deliberate processes 

by which CO2 is either removed from the atmosphere or 

diverted from emission sources and stored in the ocean, terrestrial environments (vegetation, soils, and sediment), and 

geologic formations.

enhanced oil recovery Injection of steam, gas, or other 

chemical compounds into hydrocarbon reservoirs to stimulate 

the production of usable oil beyond what is possible through 

natural pressure, water injection, and pumping at the wellhead.

federally owned offshore areas Federal jurisdiction begins 

at 3 geographic (nautical) miles from the established baseline 

for the coast and extends to an outer limit of 200 nautical 

miles. However, there are special cases. Because of claims 

existing at the dates of statehood, Texas and the Gulf Coast of 

Florida have proprietary interest in a submerged belt of land, 

9 geographic miles wide, extending seaward along the coast 

(Thormahlen, 1999). Resource assessments in federally owned 

offshore areas are typically done by the Bureau of Ocean 

Energy Management (BOEM).

gas:oil ratio (GOR) Ratio of gas to oil (in cubic feet per 

barrel) in a hydrocarbon accumulation. GOR is calculated by 

using volumes of gas and oil at surface conditions.

gas reservoir A subsurface accumulation of hydrocarbons 

primarily in the gas phase that is contained in porous or 

fractured rock formations. A gas accumulation is defined by 

the USGS (Klett and others, 2005) as having a gas:oil ratio of 

20,000 cubic feet per barrel or greater.

geologic storage of CO2 A type of carbon sequestration that 

utilizes the long-term retention of carbon dioxide in subsurface 

geologic formations.

injectivity The “Schlumberger Oilfield Glossary” (Schlumberger, 2011) defines an injectivity test as a procedure that is 

used to determine “the rate and pressure at which fluids can be 

pumped into the treatment target without fracturing the formation.” Although injectivity is typically reported as a rate, the 

methodology used in this assessment addresses this requirement by using permeability values to divide the residual 

storage component of the storage formation into three classes; 

see residual trapping classes 1, 2, and 3. The permeability is a 

proxy for injectivity because actual CO2 injection rate data are 

generally limited to enhanced-oil-recovery operations using 

CO2 and are not available for various reservoir types.

known recovery production volumes The cumulative petroleum production and proved reserves for a given reservoir.

known recovery replacement storage resource (KRRSR) The 

storage resource calculated from known recovery production 

volumes.

minimum size The lower limit for inclusion of oil and gas 

field information in assessment calculations. Following USGS 

oil and gas assessment methodology (Schmoker and Klett, 

2005), volumetric data from accumulations with less than 

0.5 million barrels of oil equivalent total production were not 

included in any of the calculations in the methodology used 

for this assessment.

National Oil and Gas Assessment (NOGA) U.S. Geological Survey National Oil and Gas Assessment, described 

at http://energy.usgs.gov/OilGas/AssessmentsData/

NationalOilGasAssessment.aspx.

Glossary
22 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

oil reservoir A subsurface accumulation of hydrocarbons 

composed primarily of oil that is contained in porous or fractured rock formations. An oil accumulation is defined by the 

USGS (Klett and others, 2005) as having a gas:oil ratio less 

than 20,000 cubic feet per barrel.

percentile In values sorted by increasing magnitude, any 

of the 99 dividers that produce exactly 100 groups with equal 

number of values (Everitt and Skrondal, 2010). The dividers 

are used to denote the proportion of values above and below 

them. The dividers are sequential integer numbers starting 

from the one between the two groups with the lowest values. 

For example, in the modeling of sequestration capacity, a 95th 

percentile of 10 Gt denotes that 10 Gt divides all likely values 

into 95 percent of them below 10 Gt and 5 percent above it.

permeability (k) A measure of the ability of a rock to permit 

fluids to be transmitted through it; it is controlled by pore size, 

pore throat geometry, and pore connectivity. Permeability is 

typically reported in darcies.

porosity (f ) The part of a rock that is occupied by voids 

or pores. Pores can be connected by passages called pore 

throats, which allow for fluid flow, or pores can be isolated 

and inaccessible to fluid flow. Porosity is typically reported as 

a volume, fraction, or percentage of the rock.

porosity of the net porous interval (fPI) For this assessment, 

three values (minimum, most likely, and maximum) were 

estimated for the mean porosity of each net porous interval. 

The determination by the assessment geologist of how much 

porosity was sufficient to allow storage of CO2 was dependent 

on the geology of the storage formation, and this dependence 

did not allow for a fixed threshold.

pressure gradient The change in pore pressure per unit 

depth, typically in units of pound-force per square inch per 

foot (psi/ft), kilopascals per meter (kPa/m), or bars per meter 

(bar/m).

residual trapping A mechanism by which CO2 is trapped 

as discrete droplets, blobs, or ganglia of CO2 as a nonwetting 

phase, essentially immiscible with the wetting fluid, within 

individual pores where the capillary forces overcome the 

buoyant forces.

residual trapping class 1 (R1) Storage formation rock with 

permeability greater than 1 darcy that is available for residual 

trapping.

residual trapping class 2 (R2) Storage formation rock with 

permeability ranging from 1 millidarcy to 1 darcy that is available for residual trapping.

residual trapping class 3 (R3) Storage formation rock 

with permeability less than 1 millidarcy that is available for 

residual trapping.

residual trapping pore volume (RPV) A calculated value equal 

to the storage formation pore volume (SFPV) minus the buoyant trapping pore volume (BPV). The value represents the pore 

volume within the storage formation that can be used to store 

CO2 by residual trapping; it is calculated during iterations of 

the Monte Carlo simulator after a value from the buoyant trapping pore volume distribution is randomly chosen by the simulator program (@RISK; version 5.7 is commercially available 

from Palisade Corporation: http://www.palisade.com/risk/). 

Calculations were made for the three residual trapping classes 

R1, R2, and R3 to obtain R1PV, R2PV, and R3PV.

residual trapping storage efficiency (RSE) A distribution of 

efficiency values that describes the fraction of residual trapping that can occur within a volume of porous media. The 

values used in the methodology for this assessment to define 

the distribution were calculated for each storage assessment 

unit by using equations from MacMinn and others (2010) and 

regional pressure and temperature data (Blondes, Brennan, and 

others, 2013). Calculations were made for the three residual 

trapping classes R1, R2, and R3 to obtain R1SE, R2SE, and R3SE.

residual trapping storage resource (RSR) The mass of CO2

retained in the storage formation by residual trapping. Calculations were made for the three residual trapping classes R1, R2, 

and R3 to obtain R1SR, R2SR, and R3SR.

residual trapping storage volume (RSV) The volume of CO2

retained in the storage formation by residual trapping. Calculations were made for the three residual trapping classes R1, R2, 

and R3 to obtain R1SV, R2SV, and R3SV.

seal A geologic feature that inhibits the mixing or migration 

of fluids and gases between adjacent geologic units. A seal is 

typically a rock unit or a fault; it can be a top seal, inhibiting 

upward flow of buoyant fluids, or a lateral seal, inhibiting the 

lateral flow of buoyant fluids.

seal formation The confining rock unit within the storage 

assessment unit. The seal formation is a rock unit that sufficiently overlies the storage formation and where managed 

properly has a capillary entrance pressure low enough to effectively inhibit the upward buoyant flow of CO2

.

State waters State jurisdiction begins at the established 

baseline for the coast and extends 3 geographic (nautical) 

miles. However, there are special cases. Because of claims 

existing at the dates of statehood, Texas and the Gulf Coast of 

Florida have proprietary interest in a submerged belt of land, 

9 geographic miles wide, extending seaward along the coast 

(Thormahlen, 1999).

storage assessment unit (SAU) A mappable volume of rock 

that includes two main components: (1) the storage formation 

(SF), which is a reservoir for CO2 storage, and (2) a regional 

seal formation.

storage assessment unit code For each storage assessment unit, the nine-digit code (shown in table 3) identifies the 

USGS-specific storage assessment unit. The preceding letter 

“C” refers to a carbon dioxide storage assessment unit and 

distinguishes it from USGS National Oil and Gas Assessment 

(NOGA) Project assessment units that may have similar numbers. The first digit after “C” of the code denotes the world 

region number (5), the following three digits (034) denote the 

North America NOGA province number, the following two 
Glossary 23

digits (C5034xx) denote the basin number (always 01 unless 

there is more than one basin in each province). The last two 

digits (C503401xx) denote the storage assessment unit number 

of that particular basin. In this report, the NOGA province and 

basin names are the same.

storage efficiency factor (BSE and RSE) Values representing the fraction of the total available pore space that will be 

occupied by free-phase CO2. Ranges of storage efficiency are 

specific to trapping types. The two used in this assessment 

were buoyant trapping storage efficiency (BSE) and residual 

trapping storage efficiency (RSE).

storage formation (SF) The reservoir of the storage assessment unit. The storage formation consist of sedimentary rock 

layers that are saturated with formation water having total 

dissolved solids (TDS) greater than 10,000 mg/L. In the CO2

assessment methodology, the storage formation resource 

calculation is the main resource calculation and consists of 

two parts: a buoyant trapping resource and a residual trapping 

resource.

storage formation pore volume (SFPV) The available pore 

space in the storage formation calculated from the area of 

the storage formation within the SAU and the thickness and 

porosity of the net porous interval. This value was used in the 

calculation of the residual trapping pore volume (RPV).

technically accessible storage resource (TASR) The mass 

of CO2 that may be injected and stored using present-day 

geologic and hydrologic knowledge of the subsurface and 

engineering practices. This term is analogous to the term 

“technically recoverable resource” used in USGS oil and gas 

assessments.

technically accessible storage volume (TASV) The volume 

of CO2 that may be injected and stored using present-day 

geologic and hydrologic knowledge of the subsurface and 

engineering practices.

thickness of the net porous interval (TPI) Defined in the 

methodology for this assessment as the mean net stratigraphic 

thickness of the portion of the storage formation that the 

assessment geologist determined contained an appropriate 

lithology with sufficient porosity to store CO2. Three values 

(minimum, most likely, and maximum) were estimated for the 

mean thickness of each net porous interval.

total dissolved solids (TDS) The quantity of dissolved material in a sample of water, usually expressed in milligrams per 

liter (mg/L).

total petroleum system (TPS) A total petroleum system 

consists of all genetically related petroleum generated by a 

pod or closely related pods of mature source rocks. Particular 

emphasis is placed on similarities of the fluids of petroleum 

accumulations (Schmoker and Klett, 2005).

trapping The physical and geochemical processes by which 

injected CO2 is retained in the subsurface.

Table 3. Estimates by the U.S. Geological 

Survey in 2012 of basin and storage assessment 

unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide 

(CO2) in the United States

Estimates are in millions of metric tons (megatons, Mt). P5, P50, and P95 are probability percentiles and represent the 5-, 50-, and 95-percent probabilities, respectively, that the true storage 

resource is less than the value shown. The percentiles were calculated by using the aggregation 

method described in the “Aggregation” section of this report and in Blondes, Schuenemeyer, and 

others (2013). Percentile values do not sum to totals because the aggregation procedure used 

partial dependencies between storage assessment units. Mean values sum to totals but are 

reported to only two significant figures if the value is greater than 1 Mt and are rounded to the 

nearest 0.1 Mt if the value is less than 1 Mt. For each storage assessment unit, the nine-digit 

code identifies the USGS-specific SAU. Components of the code are explained in the “Glossary.” 

A complete set of input parameters and results for each SAU, along with plots of the probability 

distributions for each SAU, is available in the companion assessment data publication (U.S. Geological Survey Geologic Carbon Dioxide Storage Resources Assessment Team, 2013a). Basins 

are listed alphabetically. NQ, nonquantitative SAU.
26 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.

SAU code SAU name

KRRSR

Known recovery replacement 

storage resource

BSR

Buoyant trapping 

storage resource

R1SR

Residual trapping class 1 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean 

Alaska North Slope (C5001) 

C50010101 Endicott Group - LCU 

Truncation 16 20 25 20 17 23 52 28 33 45 58 45 

C50010102 Endicott Group - Kayak 

Shale 9.4 12 15 12 10 14 37 18 2.2 5.0 7.3 4.9 

C50010103 Lower Ellesmerian 0.0 0.0 0.0 0.0 0.6 21 720 180 0.0 0.0 0.0 0.0 

C50010104 Lower Ellesmerian Deep 13 16 20 16 23 150 2,800 680 0.0 0.0 0.0 0.0 

C50010105 Lower Ellesmerian - 

LCU Truncation 0.0 0.0 0.0 0.0 0.1 1.8 47 11 0.0 0.0 0.0 0.0 

C50010106 Beaufortian and Upper 

Ellesmerian 660 860 1,100 860 910 1,200 2,400 1,400 0.0 0.0 0.0 0.0 

C50010107 Lower Torok Formation 0.1 0.1 0.2 0.1 550 4,600 52,000 13,000 0.0 0.0 0.0 0.0 

C50010108 Upper Torok Formation 0.0 0.0 0.0 0.0 110 430 4,400 1,100 0.0 0.0 0.0 0.0 

C50010109 Nanushuk Formation 0.0 0.0 0.0 0.0 33 140 2,000 510 0.0 0.0 0.0 0.0 

C50010110 Tuluvak Formation 0.0 0.0 0.0 0.0 21 71 430 130 0.0 0.0 0.0 0.0 

C50010111 Lower Seabee 

Formation 0.0 0.0 0.0 0.0 9.1 27 110 40 0.0 0.0 0.0 0.0 

C50010112 Middle Schrader Bluff 

Formation 0.0 0.0 0.0 0.0 8.8 31 160 51 19 32 48 32 

C50010113 Canning Formation 0.0 0.0 0.0 0.0 25 34 46 35 0.0 0.0 0.0 0.0 

C50010114 Staines Tongue 0.0 0.0 0.0 0.0 14 160 1,800 460 440 690 1,000 700 

Aggregated totals 700 910 1,100 910 2,400 8,600 62,000 18,000 510 770 1,100 760 

Anadarko and Southern Oklahoma Basins (C5058) 

C50580101 Lower Paleozoic 

Composite 21 30 41 30 25 38 230 79 450 920 1,700 990 

C50580102 Lower Paleozoic 

Composite Deep 3.1 4.4 6.0 4.4 4.0 7.2 48 15 0.0 0.0 0.0 0.0 

C50580103 Hunton Group and 

Misener Sandstone 8.0 12 17 12 10 16 57 23 0.0 0.0 0.0 0.0 

C50580104 Hunton Group and 

Misener Sandstone 

Deep 27 38 50 38 31 42 100 53 0.0 0.0 0.0 0.0 

C50580105 Mississippian 

Composite 110 180 270 180 730 1,000 2,200 1,300 0.0 0.0 0.0 0.0 

C50580106 Mississippian 

Composite Deep 18 24 30 24 140 210 530 260 0.0 0.0 0.0 0.0 

C50580107 Lower Virgilian 0.0 0.0 0.0 0.0 0.0 0.5 24 6.4 0.0 0.0 0.0 0.0 

C50580108 Chase and Council 

Grove Groups 12 16 21 16 13 18 110 45 0.0 0.0 0.0 0.0 

Aggregated totals 220 300 420 310 1,000 1,400 3,300 1,700 450 920 1,700 990 

Appalachian Basin (C5067) 

C50670101 Ordovician and 

Cambrian Composite 12 17 24 18 17 28 150 50 160 270 440 280 

C50670102 Clinton, Medina, 

and Tuscarora 

Formations 0.7 1.0 1.5 1.1 2.6 15 110 31 0.0 0.0 0.0 0.0 

C50670103 McKenzie, Lockport, 

and Newburg 

Formations 0.2 0.2 0.3 0.2 0.4 2.1 17 4.6 0.0 0.0 0.0 0.0 

C50670104 Oriskany Sandstone 6.4 8.9 12 9.1 11 18 130 40 0.0 0.0 0.0 0.0 

Aggregated totals 21 28 37 28 38 79 370 130 160 270 440 280 

Arkoma Basin (C5062) 

C50620101 Ordovician Composite 3.7 5.2 7.3 5.3 4.4 6.4 26 11 0.0 0.0 0.0 0.0 

C50620102 Hunton Group 0.0 0.0 0.0 0.0 3.0 9.8 32 13 0.0 0.0 0.0 0.0 

C50620103 Batesville Sandstone 

and Wedington 

Sandstone Member 0.0 0.0 0.0 0.0 4.1 7.8 15 8.3 0.0 0.0 0.0 0.0 

Aggregated totals 3.7 5.2 7.3 5.3 14 25 66 31 0.0 0.0 0.0 0.0 
Table 3 27

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.—Continued

R2SR

Residual trapping class 2 

storage resource

R3SR

Residual trapping class 3 

storage resource

TASR

Technically accessible 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean

Alaska North Slope (C5001)—Continued

160 210 260 210 0.1 1.6 5.8 2.1 210 280 370 280

350 480 650 490 0.8 9.5 35 13 370 510 710 520

7,700 13,000 21,000 13,000 210 2,600 10,000 3,500 9,300 16,000 28,000 17,000

25,000 39,000 57,000 40,000 900 12,000 44,000 16,000 30,000 52,000 93,000 56,000

1,900 2,800 4,000 2,900 0.8 13 51 18 1,900 2,800 4,100 2,900

13,000 21,000 33,000 22,000 12 160 620 220 15,000 23,000 35,000 24,000

65,000 100,000 150,000 100,000 1,300 17,000 65,000 23,000 77,000 130,000 240,000 140,000

5,700 9,200 14,000 9,400 120 1,500 5,700 2,000 6,800 12,000 21,000 13,000

1,100 1,800 2,800 1,900 6.2 82 310 110 1,200 2,200 4,600 2,500

460 640 860 650 7.9 100 370 130 560 860 1,500 910

120 150 180 150 2.5 31 110 41 150 220 350 230

280 450 660 460 0.6 7.2 27 9.6 330 530 850 550

81 110 150 110 1.8 24 87 31 120 170 250 180

6,900 10,000 14,000 10,000 11 150 550 200 7,600 11,000 17,000 12,000

150,000 200,000 280,000 210,000 7,600 38,000 110,000 45,000 170,000 260,000 400,000 270,000

Anadarko and Southern Oklahoma Basins (C5058)—Continued

2,500 5,300 9,800 5,600 0.0 0.0 0.0 0.0 3,200 6,300 11,000 6,600

8,400 15,000 25,000 15,000 16 220 860 300 8,600 15,000 26,000 16,000

760 1,700 3,500 1,900 0.8 11 42 15 780 1,800 3,600 1,900

2,800 4,400 6,800 4,500 53 670 2,500 890 3,300 5,300 8,400 5,500

7,200 18,000 42,000 21,000 23 300 1,200 420 8,400 20,000 44,000 22,000

2,100 3,100 4,500 3,100 36 470 1,700 620 2,500 3,900 6,100 4,000

1,600 2,900 4,800 3,000 0.0 0.0 0.0 0.0 1,600 2,900 4,800 3,000

1,900 2,600 3,600 2,700 33 430 1,600 570 2,200 3,200 4,700 3,300

34,000 55,000 88,000 57,000 670 2,500 6,100 2,800 38,000 60,000 96,000 62,000

Appalachian Basin (C5067)—Continued

3,000 4,800 7,700 5,000 38 490 1,900 660 3,500 5,700 9,300 6,000

7,200 11,000 18,000 12,000 14 190 700 250 7,300 12,000 18,000 12,000

1,000 1,600 2,400 1,600 0.0 0.2 0.9 0.3 1,000 1,600 2,400 1,600

250 550 1,000 580 6.4 87 360 120 300 680 1,400 740

13,000 18,000 27,000 19,000 180 840 2,500 1,000 14,000 20,000 29,000 20,000

Arkoma Basin (C5062)—Continued

3,100 6,500 12,000 6,900 25 330 1,200 440 3,400 6,900 13,000 7,400

190 400 730 420 1.9 24 89 32 220 440 800 460

30 66 130 71 0.1 1.1 4.2 1.5 37 75 140 80

3,500 7,000 13,000 7,400 39 360 1,300 480 3,800 7,500 13,000 7,900
28 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.

SAU code SAU name

KRRSR

Known recovery replacement 

storage resource

BSR

Buoyant trapping 

storage resource

R1SR

Residual trapping class 1 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean 

Atlantic Coastal Plain (C5070) 

C50700101 Lower Cretaceous 

Composite 0.0 0.0 0.0 0.0 39 100 270 120 1,800 2,900 4,500 3,000 

C50700102 Upper Cretaceous 

Composite 0.0 0.0 0.0 0.0 0.0 0.0 0.7 0.2 130 180 240 190 

Aggregated totals 0.0 0.0 0.0 0.0 39 100 270 120 2,000 3,100 4,700 3,200 

Bend Arch and Fort Worth Basin (C5045) 

C50450101 Chappel Limestone and 

Ellenburger Group 3.2 4.3 5.8 4.4 4.4 8.2 43 14 0.0 0.0 0.0 0.0 

C50450102 Bend Group and Comyn 

Formation 210 280 370 280 220 290 460 330 330 660 1,100 680 

Aggregated totals 210 290 370 290 230 310 500 340 330 660 1,100 680 

Bighorn Basin (C5034) 

C50340101 Tensleep Sandstone 30 40 53 41 34 44 56 45 0.0 0.0 0.0 0.0 

C50340102 Tensleep Sandstone 

Deep 0.0 0.0 0.0 0.0 0.2 0.6 1.7 0.7 0.0 0.0 0.0 0.0 

C50340103 Ervay Member 17 23 31 24 20 26 50 30 0.0 0.0 0.0 0.0 

C50340104 Ervay Member Deep 0.0 0.0 0.0 0.0 0.1 0.8 9.0 2.2 0.0 0.0 0.0 0.0 

C50340105 Crow Mountain 

Sandstone 0.0 0.0 0.0 0.0 0.3 2.0 12 3.6 0.0 0.0 0.0 0.0 

C50340106 Crow Mountain 

Sandstone Deep 0.0 0.0 0.0 0.0 0.1 0.8 4.2 1.3 0.0 0.0 0.0 0.0 

C50340107 Cloverly Formation 0.4 0.6 0.8 0.6 0.5 1.1 52 17 0.0 0.0 0.0 0.0 

C50340108 Cloverly Formation 

Deep 0.0 0.0 0.0 0.0 0.0 0.1 6.6 1.8 0.0 0.0 0.0 0.0 

C50340109 Muddy Sandstone 6.3 8.9 12 9.0 7.4 9.8 23 12 0.0 0.0 0.0 0.0 

C50340110 Muddy Sandstone Deep 0.1 0.1 0.1 0.1 0.1 0.2 1.3 0.4 0.0 0.0 0.0 0.0 

C50340111 Frontier Sandstone 14 19 25 19 16 23 71 32 0.0 0.0 0.0 0.0 

C50340112 Frontier Sandstone Deep 0.0 0.0 0.0 0.0 0.2 1.6 14 3.6 0.0 0.0 0.0 0.0 

Aggregated totals 75 93 110 93 89 120 290 150 0.0 0.0 0.0 0.0 

Black Warrior Basin (C5065) 

C50650101 Lewis Sandstone 0.0 0.1 0.1 0.1 0.1 0.3 1.4 0.5 0.0 0.0 0.0 0.0 

C50650102 Parkwood Formation 14 22 32 23 13 17 29 19 0.0 0.0 0.0 0.0 

Aggregated totals 14 23 32 23 13 17 30 19 0.0 0.0 0.0 0.0 

Central California Coast Basins (C5011) 

C50110101 Vaqueros Sandstone 

(NQ) -- -- -- -- -- -- -- -- -- -- -- -- 

Aggregated totals -- -- -- -- -- -- -- -- -- -- -- -- 

Columbia Basin of Oregon, Washington, and Idaho (C5005) 

C50050101 Eocene-Oligocene 

Composite (NQ) -- -- -- -- -- -- -- -- -- -- -- -- 

C50050102 Eocene-Oligocene 

Composite Deep 

(NQ) -- -- -- -- -- -- -- -- -- -- -- -- 

Aggregated totals -- -- -- -- -- -- -- -- -- -- -- -- 

Denver Basin (C5039) 

C50390101 Plainview and Lytle 

Formations 0.2 0.3 0.4 0.3 1.9 29 480 120 0.0 0.0 0.0 0.0 

C50390102 Muddy Sandstone 68 91 120 93 73 98 230 130 35 100 250 120 

C50390103 Greenhorn Limestone 0.0 0.0 0.0 0.0 0.0 0.3 5.2 1.3 0.0 0.0 0.0 0.0 

C50390104 Niobrara Formation and 

Codell Sandstone 0.1 0.1 0.1 0.1 16 26 87 36 0.0 0.0 0.0 0.0 

C50390105 Terry and Hygiene 

Sandstone Members 6.4 8.5 11 8.6 7.1 9.6 21 11 0.0 0.0 0.0 0.0 

Aggregated totals 76 100 130 100 110 170 850 300 35 100 250 120 
Table 3 29

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.—Continued

R2SR

Residual trapping class 2 

storage resource

R3SR

Residual trapping class 3 

storage resource

TASR

Technically accessible 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean

Atlantic Coastal Plain (C5070)—Continued

6,600 10,000 16,000 11,000 0.0 0.1 4.7 1.1 8,800 13,000 20,000 14,000

200 270 340 270 0.0 0.0 0.0 0.0 350 450 570 450

6,900 11,000 16,000 11,000 0.0 0.1 4.7 1.1 9,200 14,000 20,000 14,000

Bend Arch and Fort Worth Basin (C5045)—Continued

1,200 2,700 5,800 3,000 50 650 2,600 900 1,500 3,500 7,500 3,900

5,300 9,700 16,000 10,000 30 400 1,500 540 6,500 11,000 18,000 12,000

7,000 13,000 20,000 13,000 170 1,100 3,800 1,400 8,600 15,000 24,000 15,000

Bighorn Basin (C5034)—Continued

1.7 23 93 32 0.0 0.1 0.7 0.2 43 68 140 77

0.1 1.3 5.2 1.8 0.0 1.2 10 2.6 0.7 3.5 16 5.2

94 170 290 180 0.2 2.6 11 3.6 120 200 340 210

29 52 93 56 0.6 8.0 32 11 34 64 120 69

160 250 360 250 0.4 4.7 17 6.2 160 260 380 260

27 45 72 47 0.6 7.4 28 10 32 56 94 58

39 260 860 330 0.1 1.5 10 2.8 44 270 910 350

2.2 29 100 37 0.2 7.1 54 15 3.5 40 150 54

8.2 42 120 50 0.0 0.4 2.6 0.8 18 54 140 63

0.1 1.8 6.7 2.4 0.0 0.9 7.1 1.8 0.4 3.3 14 4.6

240 410 710 440 0.2 3.3 13 4.7 260 450 770 470

76 110 160 110 2.5 32 120 43 92 150 260 160

890 1,500 2,400 1,500 21 86 230 100 1,100 1,700 2,800 1,800

Black Warrior Basin (C5065)—Continued

43 76 120 79 0.0 0.6 2.3 0.8 43 77 130 80

120 200 340 210 0.1 1.4 5.4 1.9 130 220 370 230

170 280 450 290 0.2 2.1 7.2 2.7 180 300 480 310

Central California Coast Basins (C5011)—Continued

-- -- -- -- -- -- -- -- -- -- -- --

-- -- -- -- -- -- -- -- -- -- -- --

Columbia Basin of Oregon, Washington, and Idaho (C5005)—Continued

-- -- -- -- -- -- -- -- -- -- -- --

-- -- -- -- -- -- -- -- -- -- -- --

-- -- -- -- -- -- -- -- -- -- -- --

Denver Basin (C5039)—Continued

180 510 1,100 570 12 160 740 240 280 790 2,000 930

730 2,100 4,900 2,300 0.5 6.8 32 10 880 2,300 5,300 2,600

3.3 7.8 17 8.6 0.9 11 48 16 6.8 21 63 26

5.0 12 26 13 1.2 16 67 23 29 59 150 72

16 33 63 35 0.3 4.6 18 6.4 27 49 90 53

1,000 2,700 5,900 3,000 37 210 830 300 1,400 3,300 7,200 3,700
30 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.

SAU code SAU name

KRRSR

Known recovery replacement 

storage resource

BSR

Buoyant trapping 

storage resource

R1SR

Residual trapping class 1 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean 

Eastern Great Basin (C5019) 

C50190101 Joana Limestone (NQ) -- -- -- -- -- -- -- -- -- -- -- -- 

C50190102 Navajo Sandstone 0.9 1.2 1.6 1.2 1.2 2.2 23 6.6 0.0 0.0 0.0 0.0 

Aggregated totals 0.9 1.2 1.6 1.2 1.2 2.2 23 6.6 0.0 0.0 0.0 0.0 

Eastern Mesozoic Rift Basins (C5068) 

C50680101 Stockton Formation 0.0 0.0 0.0 0.0 1.3 2.0 19 5.9 0.0 0.0 0.0 0.0 

C50680201 New Oxford Formation 

(NQ) -- -- -- -- -- -- -- -- -- -- -- -- 

C50680301 Manassas Sandstone 

(NQ) -- -- -- -- -- -- -- -- -- -- -- -- 

Aggregated totals 0.0 0.0 0.0 0.0 1.3 2.0 19 5.9 0.0 0.0 0.0 0.0 

Greater Green River Basin (C5037) 

C50370101 Paleozoic Composite 12 16 21 16 14 21 51 25 0.0 0.0 0.0 0.0 

C50370102 Paleozoic Composite 

Deep 9.1 12 15 12 11 24 450 120 0.0 0.0 0.0 0.0 

C50370103 Nugget Sandstone 0.4 0.7 0.9 0.7 1.1 3.1 13 4.6 0.0 0.0 0.0 0.0 

C50370104 Nugget Sandstone Deep 1.4 1.8 2.3 1.8 2.1 8.2 170 42 0.0 0.0 0.0 0.0 

C50370105 Muddy Sandstone and 

Cloverly Formation 81 120 160 120 93 120 160 120 0.0 0.0 0.0 0.0 

C50370106 Muddy Sandstone and 

Cloverly Formation 

Deep 4.6 6.0 7.4 6.0 5.2 7.1 21 9.7 0.0 0.0 0.0 0.0 

C50370107 Frontier Sandstone 190 260 380 270 210 270 380 290 0.0 0.0 0.0 0.0 

C50370108 Frontier Sandstone Deep 0.3 0.4 0.5 0.4 0.5 2.2 27 6.8 0.0 0.0 0.0 0.0 

C50370109 Hilliard, Baxter, and 

Mancos Shales 2.2 3.2 4.6 3.3 2.6 3.8 28 9.9 0.0 0.0 0.0 0.0 

C50370110 Hilliard, Baxter, and 

Mancos Shales Deep 0.0 0.0 0.0 0.0 0.0 0.0 2.1 0.6 0.0 0.0 0.0 0.0 

C50370111 Mesaverde Group 21 30 42 30 23 31 89 47 0.0 0.0 0.0 0.0 

C50370112 Mesaverde Group Deep 0.0 0.0 0.0 0.0 0.0 0.7 28 7.1 0.0 0.0 0.0 0.0 

C50370113 Dad Member 31 44 64 45 35 47 75 50 0.0 0.0 0.0 0.0 

C50370114 Dad Member Deep 0.1 0.1 0.1 0.1 0.1 0.2 2.1 0.6 0.0 0.0 0.0 0.0 

Aggregated totals 380 500 650 500 440 580 1,500 740 0.0 0.0 0.0 0.0 

Hanna, Laramie, and Shirley Basins (C5030) 

C50300101 Paleozoic Composite 0.4 0.6 0.8 0.6 0.7 2.2 23 6.1 5.2 12 23 12 

C50300102 Paleozoic Composite 

Deep 0.0 0.0 0.0 0.0 0.0 0.3 3.2 0.8 0.0 0.0 0.0 0.0 

C50300103 Muddy Sandstone and 

Cloverly Formation 0.4 0.5 0.7 0.5 0.4 0.6 17 5.8 0.0 0.0 0.0 0.0 

C50300104 Muddy Sandstone and 

Cloverly Formation 

Deep 0.0 0.0 0.0 0.0 0.0 0.0 2.5 0.7 0.0 0.0 0.0 0.0 

C50300105 Frontier Sandstone 0.0 0.0 0.0 0.0 0.0 0.1 0.7 0.2 0.0 0.0 0.0 0.0 

C50300106 Frontier Sandstone Deep 0.0 0.0 0.0 0.0 0.0 0.1 0.2 0.1 0.0 0.0 0.0 0.0 

C50300107 Shannon Sandstone 

Member 0.0 0.0 0.0 0.0 0.1 0.3 1.3 0.5 0.0 0.0 0.0 0.0 

C50300108 Shannon Sandstone 

Member Deep 0.0 0.0 0.0 0.0 0.1 0.2 0.4 0.2 0.0 0.0 0.0 0.0 

C50300109 Mesaverde Formation 0.0 0.0 0.0 0.0 4.6 34 240 68 0.0 0.0 0.0 0.0 

C50300110 Mesaverde Formation 

Deep 0.0 0.0 0.0 0.0 0.3 3.4 35 9.0 0.0 0.0 0.0 0.0 

C50300111 Dad Member 0.0 0.0 0.0 0.0 3.0 15 79 25 0.0 0.0 0.0 0.0 

C50300112 Dad Member Deep 0.0 0.0 0.0 0.0 0.3 1.7 12 3.3 0.0 0.0 0.0 0.0 

Aggregated totals 0.9 1.1 1.4 1.1 17 74 370 120 5.2 12 23 12 
Table 3 31

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.—Continued

R2SR

Residual trapping class 2 

storage resource

R3SR

Residual trapping class 3 

storage resource

TASR

Technically accessible 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean

Eastern Great Basin (C5019)—Continued

-- -- -- -- -- -- -- -- -- -- -- --

80 170 360 190 1.9 24 97 34 98 210 430 230

80 170 360 190 1.9 24 97 34 98 210 430 230

Eastern Mesozoic Rift Basins (C5068)—Continued

130 280 510 290 7.6 100 410 140 180 400 830 440

-- -- -- -- -- -- -- -- -- -- -- --

-- -- -- -- -- -- -- -- -- -- -- --

130 280 510 290 7.6 100 410 140 180 400 830 440

Greater Green River Basin (C5037)—Continued

760 1,500 2,900 1,600 17 230 890 310 930 1,800 3,400 1,900

3,700 7,000 12,000 7,400 180 2,300 9,500 3,300 4,900 9,900 20,000 11,000

200 420 770 440 0.7 9.5 37 13 210 440 790 460

4,300 6,000 8,500 6,200 71 910 3,300 1,200 4,800 7,200 11,000 7,400

170 740 1,800 820 1.7 28 150 45 300 900 2,000 990

330 720 1,500 790 0.5 6.7 30 9.8 340 740 1,500 810

110 280 670 320 3.3 45 210 68 380 620 1,200 680

0.0 0.0 0.0 0.0 6.3 92 470 150 9.4 98 490 150

2,400 4,300 7,300 4,500 51 650 2,500 870 2,900 5,200 8,700 5,400

140 280 440 290 16 210 840 290 220 500 1,200 580

4,200 7,100 11,000 7,300 45 580 2,200 780 4,700 7,900 12,000 8,100

170 280 430 290 13 170 660 230 230 470 1,000 530

460 920 1,700 970 4.7 62 250 86 550 1,000 1,900 1,100

17 58 120 62 2.0 30 150 47 25 95 250 110

21,000 30,000 43,000 31,000 1,700 6,200 17,000 7,400 26,000 38,000 57,000 39,000

Hanna, Laramie, and Shirley Basins (C5030)—Continued

180 370 710 400 0.1 0.9 3.6 1.2 190 390 750 420

16 79 200 90 0.6 11 60 18 20 95 250 110

5.3 70 270 95 0.0 0.6 4.5 1.2 6.9 75 290 100

0.7 8.6 32 12 0.1 2.0 16 4.2 1.0 12 47 16

65 130 230 130 0.1 1.8 7.3 2.5 67 130 230 140

10 16 23 16 0.8 10 37 14 14 27 56 30

16 77 200 89 0.3 4.4 25 7.5 17 84 220 97

4.0 14 30 15 0.5 7.9 39 12 6.6 24 63 28

170 560 1,200 610 0.3 4.9 23 7.4 210 630 1,400 690

290 480 680 480 1.6 21 77 28 310 510 740 520

27 89 190 96 0.1 0.8 3.6 1.2 40 110 240 120

12 21 32 21 0.5 7.0 27 9.5 16 31 60 34

1,100 2,000 3,200 2,100 25 91 240 110 1,300 2,200 3,600 2,300
32 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.

SAU code SAU name

KRRSR

Known recovery replacement 

storage resource

BSR

Buoyant trapping 

storage resource

R1SR

Residual trapping class 1 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean 

Illinois Basin (C5064) 

C50640101 Mount Simon Sandstone 0.0 0.0 0.0 0.0 53 230 1,100 370 840 1,400 2,200 1,400 

C50640102 Ordovician Composite 26 33 41 33 27 37 120 55 0.0 0.0 0.0 0.0 

C50640103 Devonian and Silurian 

Composite 41 52 65 52 5.0 6.9 15 8.0 37 72 110 72 

Aggregated totals 69 85 100 85 94 290 1,300 440 900 1,400 2,300 1,500 

Kandik Basin (C5002) 

C50020101 Nation River Formation 0.0 0.0 0.0 0.0 0.3 4.3 59 14 0.0 0.0 0.0 0.0 

C50020102 Step Conglomerate and 

Tahkandit Limestone 0.0 0.0 0.0 0.0 0.3 5.3 97 23 0.0 0.0 0.0 0.0 

Aggregated totals 0.0 0.0 0.0 0.0 1.1 13 150 38 0.0 0.0 0.0 0.0 

Kansas Basins (C5056) 

C50560101 Lower Paleozoic 

Composite 3.8 4.9 6.0 4.9 3.9 5.2 8.2 5.5 0.0 0.0 0.0 0.0 

C50560102 Hunton Group 0.6 0.8 1.0 0.8 0.7 0.9 1.4 0.9 0.0 0.0 0.0 0.0 

Aggregated totals 4.5 5.6 6.9 5.7 4.8 6.1 9.2 6.5 0.0 0.0 0.0 0.0 

Los Angeles Basin (C5014) 

C50140101 Repetto and Puente 

Formations 9.7 13 16 13 42 73 130 79 66 130 230 130 

C50140102 Repetto and Puente 

Formations Deep 0.0 0.0 0.0 0.0 0.5 1.6 5.1 2.0 0.0 0.0 0.0 0.0 

Aggregated totals 10 13 16 13 43 75 140 81 66 130 230 130 

Michigan Basin (C5063) 

C50630101 Ordovician and 

Cambrian Composite 41 55 71 55 55 95 420 150 2,700 4,500 6,800 4,600 

C50630102 Salina Group and 

Middle Silurian 

Composite 83 110 140 110 110 150 410 190 0.0 0.0 0.0 0.0 

C50630103 Sylvania and Bois Blanc 

Formations and Bass 

Islands Dolomite 

(NQ) -- -- -- -- -- -- -- -- -- -- -- -- 

C50630104 Dundee Formation 9.8 12 15 12 10 13 29 16 29 38 51 39 

Aggregated totals 140 180 220 180 190 280 790 360 2,800 4,500 6,800 4,600 

Palo Duro Basin (C5043) 

C50430101 Basin Center Paleozoic 

Composite 1.0 1.4 1.7 1.4 1.2 1.8 9.9 3.6 29 55 95 57 

C50430102 Basin Flank Paleozoic 

Composite 58 77 99 78 0.1 0.8 8.5 2.2 38 57 80 58 

C50430103 Basin Center Permian 56 74 96 75 0.0 0.5 15 3.6 0.0 0.0 0.0 0.0 

Aggregated totals 120 150 190 150 1.6 4.1 32 9.3 72 110 170 120 

Paradox Basin (C5021) 

C50210101 Paleozoic Composite 36 51 71 52 45 63 160 78 0.0 0.0 0.0 0.0 

Aggregated totals 36 51 71 52 45 63 160 78 0.0 0.0 0.0 0.0 

Permian Basin (C5044) 

C50440101 Lower Paleozoic 

Composite 470 680 960 690 640 860 1,800 1,100 1,400 2,800 5,300 3,000 

C50440102 Lower Paleozoic 

Composite Deep 330 430 550 440 440 570 860 620 610 1,000 1,600 1,000 

C50440103 Permian Composite 160 210 270 210 420 560 1,200 680 39 75 130 77 

Aggregated totals 1,000 1,300 1,700 1,300 1,600 2,000 4,000 2,400 2,200 3,900 6,700 4,100 
Table 3 33

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.—Continued

R2SR

Residual trapping class 2 

storage resource

R3SR

Residual trapping class 3 

storage resource

TASR

Technically accessible 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean

Illinois Basin (C5064)—Continued

59,000 86,000 130,000 88,000 190 2,500 8,900 3,200 62,000 91,000 130,000 94,000

37,000 53,000 74,000 53,000 150 1,900 7,000 2,500 38,000 55,000 77,000 56,000

2,300 3,600 5,200 3,600 16 210 790 280 2,500 3,900 5,800 4,000

110,000 140,000 200,000 150,000 1,000 5,100 14,000 6,100 110,000 150,000 210,000 150,000

Kandik Basin (C5002)—Continued

200 580 1,200 620 5.0 74 350 110 240 690 1,400 740

180 530 1,200 580 5.4 77 350 120 220 660 1,500 720

480 1,100 2,200 1,200 22 170 630 230 570 1,400 2,700 1,500

Kansas Basins (C5056)—Continued

130 240 420 250 0.9 11 47 16 140 260 450 270

25 44 75 46 0.1 0.7 2.9 1.0 26 46 77 48

160 280 480 300 1.5 12 48 17 180 300 510 320

Los Angeles Basin (C5014)—Continued

1,400 2,600 4,700 2,800 0.0 0.1 0.7 0.2 1,600 2,800 5,000 3,000

580 730 910 740 0.1 1.4 5.6 2.0 580 740 920 740

2,000 3,300 5,600 3,500 0.1 1.6 6.2 2.2 2,200 3,500 5,800 3,700

Michigan Basin (C5063)—Continued

19,000 29,000 43,000 30,000 210 2,600 9,500 3,400 24,000 37,000 54,000 38,000

11,000 17,000 26,000 17,000 40 520 1,900 700 12,000 18,000 27,000 18,000

-- -- -- -- -- -- -- -- -- -- -- --

360 480 620 480 2.6 34 120 44 430 570 760 580

33,000 47,000 66,000 48,000 560 3,300 11,000 4,200 40,000 56,000 78,000 57,000

Palo Duro Basin (C5043)—Continued

1,000 1,800 3,100 1,900 0.4 6.1 24 8.4 1,000 1,900 3,200 2,000

1,200 1,700 2,200 1,700 0.6 8.6 31 11 1,300 1,700 2,300 1,800

2,200 3,300 4,800 3,400 2.7 35 130 48 2,200 3,300 4,900 3,400

4,900 6,900 9,400 7,000 9.0 56 170 67 5,100 7,100 9,600 7,200

Paradox Basin (C5021)—Continued

1,000 2,500 5,300 2,800 28 380 1,600 530 1,300 3,100 6,300 3,400

1,000 2,500 5,300 2,800 28 380 1,600 530 1,300 3,100 6,300 3,400

Permian Basin (C5044)—Continued

12,000 24,000 45,000 26,000 63 850 3,400 1,200 16,000 29,000 53,000 31,000

10,000 16,000 23,000 16,000 53 690 2,500 910 12,000 18,000 27,000 19,000

4,700 8,000 13,000 8,300 30 400 1,600 550 5,500 9,200 15,000 9,600

31,000 48,000 75,000 50,000 460 2,200 6,400 2,600 37,000 57,000 89,000 59,000
34 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.

SAU code SAU name

KRRSR

Known recovery replacement 

storage resource

BSR

Buoyant trapping 

storage resource

R1SR

Residual trapping class 1 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean 

Powder River Basin (C5033) 

C50330101 Minnelusa and Tensleep 

Sandstones 32 43 57 43 35 48 130 64 0.0 0.0 0.0 0.0 

C50330102 Crow Mountain 

Sandstone 0.0 0.0 0.0 0.0 0.0 0.3 3.1 0.8 0.0 0.0 0.0 0.0 

C50330103 Lower Sundance 

Formation 1.2 1.6 2.1 1.6 1.3 1.7 5.0 2.5 0.0 0.0 0.0 0.0 

C50330104 Fall River and Lakota 

Formations 7.8 11 14 11 13 33 170 56 0.0 0.0 0.0 0.0 

C50330105 Muddy Sandstone 27 37 50 38 33 48 220 81 0.3 1.8 4.1 2.0 

C50330106 Frontier Sandstone 

and Turner Sandy 

Member 6.4 8.8 12 8.9 7.2 10 37 16 0.0 0.0 0.0 0.0 

C50330107 Sussex and Shannon 

Sandstone Members 8.6 11 15 11 9.0 12 30 16 0.0 0.0 0.0 0.0 

C50330108 Parkman Sandstone 

Member 2.2 2.9 3.6 2.9 2.4 3.2 32 19 0.0 0.0 0.0 0.0 

C50330109 Teapot Sandstone 

Member 1.2 1.6 2.0 1.6 1.3 1.8 18 10 0.0 0.0 0.0 0.0 

C50330110 Teckla Sandstone 

Member 1.1 1.4 1.8 1.4 1.2 1.6 21 12 0.0 0.0 0.0 0.0 

Aggregated totals 96 120 150 120 120 180 710 280 0.3 1.8 4.1 2.0 

Raton Basin (C5041) 

C50410101 Dakota Sandstone (NQ) -- -- -- -- -- -- -- -- -- -- -- -- 

Aggregated totals -- -- -- -- -- -- -- -- -- -- -- -- 

Sacramento Basin (C5009) 

C50090101 Kione Sands of Forbes 

Formation 0.0 0.0 0.0 0.0 0.1 0.6 7.0 1.8 0.0 0.0 0.0 0.0 

C50090102 Winters Formation 16 26 39 26 20 28 67 36 340 570 890 590 

C50090103 Starkey Sands of the 

Moreno Formation 2.2 3.4 5.1 3.5 3.1 4.8 45 14 0.0 0.0 0.0 0.0 

C50090104 Mokelumne River 

Formation 11 16 22 16 13 18 44 23 96 160 260 170 

C50090105 Domengine Formation 2.2 3.0 3.9 3.0 2.7 3.7 9.9 4.7 0.0 0.0 0.0 0.0 

Aggregated totals 34 48 67 49 42 57 180 80 460 740 1,100 760 

San Joaquin Basin (C5010) 

C50100101 Lathrop Sand of the 

Panoche Formation 0.6 0.9 1.4 1.0 0.8 1.2 11 3.5 410 720 1,100 730 

C50100102 Moreno Formation 

Sands 1.4 2.2 3.4 2.3 1.8 2.6 12 4.5 300 520 800 530 

C50100103 Domengine Formation 0.1 0.2 0.2 0.2 1.0 6.3 43 12 0.0 0.0 0.0 0.0 

C50100104 Temblor Formation 14 20 26 20 19 42 530 140 320 630 1,100 650 

C50100105 Temblor Formation 

Deep 0.0 0.0 0.0 0.0 0.1 1.7 23 5.6 0.0 0.0 0.0 0.0 

C50100106 Stevens Sand of the 

Monterey Formation 0.4 0.6 0.7 0.6 0.9 12 400 97 320 560 850 570 

C50100107 Stevens Sand of the 

Monterey Formation 

Deep 0.6 0.7 0.9 0.8 0.7 1.3 14 3.8 0.0 0.0 0.0 0.0 

Aggregated totals 18 24 32 25 31 98 980 270 1,600 2,400 3,400 2,500 

San Juan Basin (C5022) 

C50220101 Entrada Sandstone 0.2 0.2 0.3 0.2 0.2 0.4 1.5 0.6 3.8 8.4 17 9.1 

C50220102 Dakota Sandstone 0.5 0.6 0.9 0.7 0.6 0.9 4.8 1.6 0.0 0.0 0.0 0.0 

C50220103 Gallup Sandstone 8.6 11 15 11 9.1 12 26 15 0.0 0.0 0.0 0.0 

C50220104 Lewis Shale and 

Mesaverde Group 0.0 0.0 0.0 0.0 0.8 1.1 3.5 1.8 0.0 0.0 0.0 0.0 

Aggregated totals 9.4 12 16 12 11 15 37 19 3.8 8.4 17 9.1 
Table 3 35

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.—Continued

R2SR

Residual trapping class 2 

storage resource

R3SR

Residual trapping class 3 

storage resource

TASR

Technically accessible 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean

Powder River Basin (C5033)—Continued

2,900 4,800 7,600 5,000 0.2 3.4 14 4.8 2,900 4,900 7,700 5,100

15 41 92 45 0.1 0.8 3.8 1.2 15 42 96 47

610 1,400 2,600 1,500 0.0 0.0 0.3 0.1 610 1,400 2,600 1,500

1,500 2,600 4,300 2,700 0.0 0.0 0.3 0.0 1,500 2,600 4,400 2,700

340 740 1,500 800 0.3 4.9 21 7.1 390 810 1,700 890

1,000 1,900 3,400 2,000 3.3 43 180 60 1,100 1,900 3,500 2,100

430 880 1,800 970 3.8 50 220 72 470 970 1,900 1,100

1,100 3,000 5,800 3,200 1.8 28 130 41 1,200 3,000 5,900 3,200

420 1,100 2,100 1,200 0.8 11 50 16 430 1,100 2,200 1,200

15 200 750 260 0.1 1.7 13 3.6 18 210 790 280

11,000 17,000 25,000 18,000 39 170 510 210 11,000 18,000 26,000 18,000

Raton Basin (C5041)—Continued

-- -- -- -- -- -- -- -- -- -- -- --

-- -- -- -- -- -- -- -- -- -- -- --

Sacramento Basin (C5009)—Continued

930 1,300 2,000 1,400 0.0 0.0 0.0 0.0 930 1,300 2,000 1,400

5,900 9,900 15,000 10,000 0.0 0.0 1.5 0.3 6,400 10,000 16,000 11,000

7,400 12,000 17,000 12,000 0.0 2.0 9.2 2.9 7,400 12,000 17,000 12,000

1,900 3,000 4,500 3,100 0.0 0.0 0.0 0.0 2,100 3,200 4,800 3,300

1,500 2,200 3,200 2,200 0.0 0.0 0.0 0.0 1,500 2,200 3,200 2,200

19,000 28,000 39,000 29,000 0.0 2.3 10 3.2 20,000 29,000 40,000 29,000

San Joaquin Basin (C5010)—Continued

9,600 16,000 23,000 16,000 0.0 0.0 0.0 0.0 10,000 17,000 24,000 17,000

6,900 11,000 17,000 12,000 0.0 0.0 0.0 0.0 7,400 12,000 17,000 12,000

200 400 730 420 1.2 16 60 21 210 430 780 450

7,300 13,000 21,000 13,000 0.0 0.0 0.0 0.0 7,900 14,000 22,000 14,000

800 1,100 1,400 1,100 3.3 44 150 56 840 1,100 1,500 1,100

3,200 5,300 7,800 5,400 0.1 2.2 11 3.4 3,700 5,900 8,700 6,000

160 250 340 250 3.0 39 150 52 190 290 460 300

33,000 48,000 65,000 48,000 25 120 300 130 36,000 51,000 69,000 51,000

San Juan Basin (C5022)—Continued

140 290 550 310 0.0 0.0 0.0 0.0 150 300 570 320

33 62 110 66 1.4 18 70 25 43 86 170 93

82 190 410 210 0.0 0.1 0.5 0.2 93 210 430 230

46 82 140 85 0.7 9.2 36 13 53 95 160 100

380 640 1,100 670 5.2 30 94 37 430 710 1,200 740
36 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.

SAU code SAU name

KRRSR

Known recovery replacement 

storage resource

BSR

Buoyant trapping 

storage resource

R1SR

Residual trapping class 1 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean 

South Florida Basin (C5050) 

C50500101 Pre-Punta Gorda 0.0 0.0 0.0 0.0 3.7 51 710 170 0.0 0.0 0.0 0.0 

C50500102 Sunniland Formation 6.7 8.5 10 8.5 8.9 21 95 32 0.0 0.0 0.0 0.0 

C50500103 Gordon Pass and Marco 

Junction Formations 0.0 0.0 0.0 0.0 0.1 2.5 68 17 0.0 0.0 0.0 0.0 

C50500104 Dollar Bay Formation 0.0 0.0 0.0 0.0 0.2 2.5 38 9.2 0.0 0.0 0.0 0.0 

C50500105 Cedar Keys and Lawson 

Formations 0.0 0.0 0.0 0.0 0.0 0.0 13 8.0 0.0 0.0 0.0 0.0 

Aggregated totals 6.7 8.5 10 8.5 21 97 900 240 0.0 0.0 0.0 0.0 

Uinta and Piceance Basins (C5020) 

C50200101 Paleozoic Composite 31 42 56 43 35 48 98 56 0.0 0.0 0.0 0.0 

C50200102 Paleozoic Composite 

Deep 0.0 0.0 0.0 0.0 0.0 0.3 6.7 1.6 0.0 0.0 0.0 0.0 

C50200103 Lower Cretaceous 

Composite 4.3 6.1 8.4 6.2 5.2 7.4 21 9.7 0.0 0.0 0.0 0.0 

C50200104 Lower Cretaceous 

Composite Deep 0.7 1.0 1.3 1.0 1.0 1.5 3.8 1.9 0.0 0.0 0.0 0.0 

C50200105 Green River Formation 6.9 9.2 12 9.2 1.3 9.0 160 40 0.0 0.0 0.0 0.0 

Aggregated totals 46 58 75 59 47 73 280 110 0.0 0.0 0.0 0.0 

U.S. Gulf Coast (C5047 and C5049) 

C50490101 Norphlet Formation 0.1 0.1 0.1 0.1 35 48 63 48 0.0 0.0 0.0 0.0 

C50490102 Norphlet Formation 

Deep 63 82 100 83 81 130 560 210 0.0 0.0 0.0 0.0 

C50490103 Smackover Formation 70 97 130 99 82 120 550 210 0.0 0.0 0.0 0.0 

C50490104 Smackover Formation 

Deep 140 180 240 190 160 220 630 290 0.0 0.0 0.0 0.0 

C50490105 Haynesville Formation 180 250 340 250 200 260 370 270 0.0 0.0 0.0 0.0 

C50490106 Haynesville Formation 

Deep 44 57 71 57 48 61 76 62 0.0 0.0 0.0 0.0 

C50490107 Sligo and Hosston 

Formations and 

Cotton Valley Group 1,300 1,800 2,600 1,900 1,400 2,000 6,600 3,200 23,000 42,000 70,000 44,000 

C50490108 Sligo and Hosston 

Formations and 

Cotton Valley Group 

Deep 46 60 75 60 56 90 520 170 0.0 0.0 0.0 0.0 

C50490109 Knowles and Winn 

Limestones and 

Calvin Sandstone 

(NQ) -- -- -- -- -- -- -- -- -- -- -- -- 

C50490110 Rodessa Formation and 

James Limestone 160 220 310 230 180 240 390 260 150 320 670 350 

C50490111 Rodessa Formation and 

James Limestone 

Deep 8.3 11 13 11 9.3 13 43 19 0.0 0.0 0.0 0.0 

C50490112 Fredericksburg Group 

and Rusk Formation 43 59 81 60 50 70 180 89 470 900 1,800 990 

C50490113 Edwards, Glen 

Rose, and James 

Limestones 10 15 21 15 13 18 31 19 0.0 0.0 0.0 0.0 

C50490114 Washita and 

Fredericksburg 

Groups, Rusk 

Formation, and 

James Limestone 56 81 110 83 66 92 390 160 0.0 0.0 0.0 0.0 
Table 3 37

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.—Continued

R2SR

Residual trapping class 2 

storage resource

R3SR

Residual trapping class 3 

storage resource

TASR

Technically accessible 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean

South Florida Basin (C5050)—Continued

66,000 100,000 140,000 100,000 300 3,800 14,000 5,100 69,000 100,000 150,000 110,000

1,100 1,200 1,400 1,200 0.0 0.0 0.2 0.0 1,100 1,300 1,500 1,300

19,000 27,000 36,000 27,000 180 2,400 8,600 3,100 21,000 30,000 41,000 30,000

4,200 6,400 9,000 6,400 46 600 2,200 790 4,600 7,100 10,000 7,200

18,000 21,000 24,000 21,000 0.0 0.0 0.0 0.0 18,000 21,000 24,000 21,000

120,000 160,000 200,000 160,000 1,400 7,600 21,000 9,000 120,000 160,000 210,000 170,000

Uinta and Piceance Basins (C5020)—Continued

590 1,100 1,900 1,100 14 180 690 240 750 1,400 2,400 1,400

0.0 0.0 0.0 0.0 32 420 1,600 560 34 430 1,600 560

250 470 790 490 13 180 670 240 340 680 1,300 730

33 62 110 65 4.5 60 240 83 53 130 320 150

260 490 910 530 17 220 900 310 360 780 1,700 880

1,300 2,200 3,300 2,200 290 1,200 3,300 1,400 2,000 3,500 6,300 3,800

U.S. Gulf Coast (C5047 and C5049)—Continued

31,000 50,000 76,000 51,000 0.0 0.0 0.0 0.0 31,000 50,000 76,000 52,000

25,000 43,000 68,000 44,000 0.0 0.0 0.0 0.0 25,000 43,000 68,000 45,000

7,900 15,000 27,000 16,000 40 520 2,100 720 8,500 16,000 29,000 17,000

21,000 31,000 47,000 32,000 94 1,200 4,500 1,600 22,000 33,000 50,000 34,000

2,800 4,600 7,200 4,700 66 850 3,200 1,100 3,600 5,900 9,500 6,100

2,200 3,800 5,900 3,900 75 970 3,700 1,300 2,800 5,000 8,700 5,200

310,000 520,000 820,000 540,000 1,100 14,000 50,000 18,000 370,000 590,000 910,000 610,000

160,000 210,000 280,000 210,000 590 7,600 27,000 9,900 170,000 220,000 300,000 220,000

-- -- -- -- -- -- -- -- -- -- -- --

3,700 6,900 13,000 7,500 2.8 43 170 59 4,200 7,600 14,000 8,200

2,000 3,300 5,500 3,400 3.9 52 200 71 2,100 3,300 5,600 3,500

5,800 9,800 17,000 10,000 5.6 75 290 100 6,600 11,000 19,000 12,000

290 520 890 550 2.8 37 140 50 340 590 990 610

2,000 4,100 8,000 4,500 13 170 690 240 2,200 4,500 8,800 4,900
38 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.

SAU code SAU name

KRRSR

Known recovery replacement 

storage resource

BSR

Buoyant trapping 

storage resource

R1SR

Residual trapping class 1 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean 

U.S. Gulf Coast (C5047 and C5049)—Continued 

C50490115 Washita and 

Fredericksburg 

Groups, Rusk 

Formation, and 

James Limestone 

Deep 37 48 58 48 39 52 77 54 0.0 0.0 0.0 0.0 

C50490116 Tuscaloosa and 

Woodbine 

Formations 290 400 530 400 350 520 1,500 680 5,000 9,700 19,000 11,000 

C50490117 Navarro, Taylor, and 

Austin Groups 120 170 240 180 150 200 480 250 0.0 0.0 0.0 0.0 

C50470118 Carrizo Sand and 

Wilcox Group 860 1,200 1,700 1,300 1,100 1,600 6,500 2,500 1,200 2,300 4,900 2,600 

C50470119 Queen City Sand 28 40 55 40 37 58 200 80 13 39 95 44 

C50470120 Sparta Sand 2.7 3.6 4.5 3.6 1.2 9.8 230 57 180 350 680 380 

C50470121 Yegua and Cockfield 

Formations 400 540 720 550 420 580 2,400 1,000 2,900 5,200 9,700 5,600 

C50470122 Frio and Vicksburg 

Formations 1,100 1,600 2,200 1,600 1,400 2,100 15,000 4,900 7,000 15,000 30,000 17,000 

C50470123 Lower Miocene I 100 150 200 150 150 250 830 340 6,500 13,000 22,000 13,000 

C50470124 Lower Miocene II 180 250 350 260 230 350 1,100 460 7,000 13,000 21,000 13,000 

C50470125 Middle Miocene 130 180 250 180 210 350 810 410 2,300 4,200 7,000 4,400 

C50470126 Upper Miocene 230 310 410 310 250 330 500 350 3,900 7,100 12,000 7,300 

C50470127 Tertiary Slope and Basin 

Floor (NQ) -- -- -- -- -- -- -- -- -- -- -- -- 

Aggregated totals 6,400 8,000 9,800 8,000 7,800 11,000 39,000 16,000 75,000 120,000 170,000 120,000 

Ventura Basin (C5013) 

C50130101 Vaqueros Sandstone and 

Sespe Formation 23 32 43 32 29 52 290 93 76 160 300 170 

Aggregated totals 23 32 43 32 29 52 290 93 76 160 300 170 

Western Oregon and Washington Basins (C5004) 

C50040101 Eocene Composite 0.0 0.0 0.0 0.0 0.1 1.5 35 8.2 860 1,600 2,700 1,700 

Aggregated totals 0.0 0.0 0.0 0.0 0.1 1.5 35 8.2 860 1,600 2,700 1,700 

Williston Basin (C5031) 

C50310101 Deadwood and Black 

Island Formations 0.3 0.4 0.5 0.4 0.6 4.4 64 15 910 1,800 3,400 1,900 

C50310102 Deadwood and Black 

Island Formations 

Deep 2.9 3.8 4.6 3.8 3.2 4.8 22 7.9 0.0 0.0 0.0 0.0 

C50310103 Winnipegosis Formation, Interlake 

Formation, and 

Bighorn Group 25 33 45 34 27 37 190 76 0.0 0.0 0.0 0.0 

C50310104 Three Forks Formation 

and Jefferson Group 5.6 7.6 10 7.7 7.3 11 56 20 0.0 0.0 0.0 0.0 

C50310105 Kibbey Formation and 

Madison Group 110 140 170 140 110 140 230 160 220 470 820 490 

C50310106 Minnelusa Group 0.9 1.1 1.4 1.1 1.0 1.6 18 5.4 0.0 0.0 0.0 0.0 

C50310107 Lower Swift Formation 0.0 0.0 0.0 0.0 39 150 540 200 0.0 0.0 0.0 0.0 

C50310108 Inyan Kara Group 0.0 0.0 0.0 0.0 31 150 700 230 240 410 610 410 

C50310109 Newcastle Formation 0.0 0.0 0.0 0.0 39 130 450 170 0.0 0.0 0.0 0.0 

Aggregated totals 150 180 230 180 340 710 2,000 880 1,600 2,700 4,400 2,800 
Table 3 39

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.—Continued

R2SR

Residual trapping class 2 

storage resource

R3SR

Residual trapping class 3 

storage resource

TASR

Technically accessible 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean

U.S. Gulf Coast (C5047 and C5049)—Continued

410 740 1,300 780 9.0 120 460 160 520 940 1,600 990

41,000 69,000 120,000 73,000 9.2 140 550 190 49,000 80,000 140,000 85,000

15,000 26,000 46,000 28,000 0.0 0.0 0.0 0.0 15,000 26,000 47,000 28,000

120,000 200,000 350,000 210,000 49 660 2,500 880 120,000 210,000 360,000 220,000

1,600 3,800 8,300 4,200 1.0 13 56 19 1,700 3,900 8,500 4,300

6,600 11,000 18,000 11,000 0.0 0.0 2.4 0.4 6,800 11,000 19,000 12,000

33,000 53,000 85,000 55,000 1.8 39 160 55 37,000 59,000 94,000 62,000

75,000 140,000 260,000 150,000 0.5 100 420 140 87,000 160,000 290,000 170,000

24,000 41,000 67,000 42,000 0.0 0.0 0.0 0.0 33,000 54,000 85,000 56,000

26,000 43,000 68,000 44,000 0.0 0.0 0.0 0.0 36,000 56,000 85,000 58,000

8,900 14,000 22,000 15,000 0.0 0.0 0.0 0.0 13,000 19,000 28,000 20,000

15,000 24,000 37,000 25,000 0.0 0.0 0.0 0.0 21,000 32,000 46,000 32,000

-- -- -- -- -- -- -- -- -- -- -- --

1,100,000 1,600,000 2,200,000 1,600,000 6,600 30,000 83,000 35,000 1,300,000 1,700,000 2,400,000 1,800,000

Ventura Basin (C5013)—Continued

3,100 5,500 9,200 5,700 0.5 9.0 35 12 3,200 5,700 9,600 6,000

3,100 5,500 9,200 5,700 0.5 9.0 35 12 3,200 5,700 9,600 6,000

Western Oregon and Washington Basins (C5004)—Continued

6,600 12,000 20,000 12,000 0.6 9.5 43 14 7,500 14,000 22,000 14,000

6,600 12,000 20,000 12,000 0.6 9.5 43 14 7,500 14,000 22,000 14,000

Williston Basin (C5031)—Continued

8,600 16,000 29,000 17,000 86 1,200 4,500 1,600 11,000 20,000 34,000 21,000

8,200 11,000 14,000 11,000 0.0 2.2 9.8 3.2 8,200 11,000 14,000 11,000

38,000 58,000 81,000 59,000 140 1,800 6,700 2,400 40,000 60,000 85,000 61,000

6,500 9,900 14,000 10,000 0.0 0.0 0.0 0.0 6,600 9,900 14,000 10,000

8,500 15,000 24,000 15,000 110 1,500 5,700 2,000 10,000 17,000 28,000 18,000

6,600 9,700 13,000 9,800 0.0 2.8 12 4.1 6,600 9,700 13,000 9,800

3,800 5,800 8,800 6,000 0.0 0.0 0.6 0.1 3,900 6,000 9,100 6,200

4,000 6,800 10,000 6,900 1.8 26 99 34 4,400 7,400 11,000 7,600

830 1,500 2,500 1,600 0.0 0.0 0.0 0.0 920 1,700 2,800 1,700

99,000 140,000 180,000 140,000 1,100 5,200 14,000 6,000 110,000 140,000 190,000 150,000
40 National Assessment of Geologic Carbon Dioxide Storage Resources—Results

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.

SAU code SAU name

KRRSR

Known recovery replacement 

storage resource

BSR

Buoyant trapping 

storage resource

R1SR

Residual trapping class 1 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean 

Wind River Basin (C5035) 

C50350101 Tensleep Sandstone 6.0 7.9 10 8.0 7.8 12 41 17 0.6 1.4 3.3 1.6 

C50350102 Tensleep Sandstone 

Deep 0.0 0.0 0.0 0.0 0.3 2.6 24 6.2 0.0 0.0 0.0 0.0 

C50350103 Nugget and Crow 

Mountain Sandstones 0.5 0.7 0.9 0.7 0.8 1.8 9.5 3.1 0.0 0.0 0.0 0.0 

C50350104 Nugget and Crow 

Mountain Sandstones 

Deep 0.0 0.0 0.0 0.0 0.0 0.3 3.8 0.9 0.0 0.0 0.0 0.0 

C50350105 Cloverly Formation 2.5 3.6 5.1 3.7 3.1 4.1 22 9.0 0.0 0.0 0.0 0.0 

C50350106 Cloverly Formation 

Deep 0.1 0.2 0.2 0.2 0.1 0.3 12 3.8 0.0 0.0 0.0 0.0 

C50350107 Muddy Sandstone 3.0 4.1 5.4 4.1 3.4 4.4 12 6.2 0.0 0.0 0.0 0.0 

C50350108 Muddy Sandstone Deep 0.8 1.0 1.4 1.1 0.9 1.1 4.3 2.1 0.0 0.0 0.0 0.0 

C50350109 Frontier Sandstone 6.0 8.7 12 8.8 7.2 9.4 15 10 0.0 0.0 0.0 0.0 

C50350110 Frontier Sandstone Deep 1.4 1.9 2.5 1.9 1.6 2.0 2.8 2.1 0.0 0.0 0.0 0.0 

C50350111 Sussex and Shannon 

Sandstone Members 0.4 0.5 0.6 0.5 0.4 0.7 11 3.1 0.0 0.0 0.0 0.0 

C50350112 Sussex and Shannon 

Sandstone Members 

Deep 6.6 8.8 11 8.9 7.1 9.5 31 15 0.0 0.0 0.0 0.0 

C50350113 Fort Union and Lance 

Formations 19 28 38 28 23 30 85 48 0.0 0.0 0.0 0.0 

Aggregated totals 52 66 81 66 63 86 280 130 0.6 1.4 3.3 1.6 

Wyoming-Idaho-Utah Thrust Belt (C5036) 

C50360101 Paleozoic Composite 73 100 140 110 84 110 200 120 0.0 0.0 0.0 0.0 

C50360102 Paleozoic Composite 

Deep 68 88 110 88 72 94 150 100 0.0 0.0 0.0 0.0 

C50360103 Nugget Sandstone 82 110 150 110 89 110 140 110 0.0 0.0 0.0 0.0 

C50360104 Nugget Sandstone Deep 2.4 3.1 4.0 3.2 2.8 4.0 10 5.0 0.0 0.0 0.0 0.0 

C50360105 Bear River Formation 0.0 0.0 0.0 0.0 14 33 79 38 0.0 0.0 0.0 0.0 

C50360106 Bear River Formation 

Deep 0.0 0.0 0.0 0.0 0.3 1.8 13 3.6 0.0 0.0 0.0 0.0 

C50360107 Frontier Sandstone 1.7 2.4 3.4 2.4 1.9 2.7 19 7.7 0.0 0.0 0.0 0.0 

C50360108 Frontier Sandstone Deep 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 

Aggregated totals 240 310 390 310 290 370 600 400 0.0 0.0 0.0 0.0 
Table 3 41

Table 3. Estimates by the U.S. Geological Survey in 2012 of basin and storage assessment unit (SAU) totals for technically accessible 

storage resources (TASR) for carbon dioxide (CO2) in the United States.—Continued

R2SR

Residual trapping class 2 

storage resource

R3SR

Residual trapping class 3 

storage resource

TASR

Technically accessible 

storage resource

P5 P50 P95 Mean P5 P50 P95 Mean P5 P50 P95 Mean

Wind River Basin (C5035)—Continued

48 110 240 120 0.0 0.0 0.0 0.0 60 130 270 140

6.3 20 56 24 0.8 12 63 19 12 40 120 50

130 220 370 230 0.0 0.0 0.0 0.0 130 220 370 230

120 200 320 210 2.5 31 120 42 140 240 400 250

91 320 740 350 0.1 1.9 9.4 2.9 97 330 770 370

210 350 520 350 7.5 100 370 130 260 470 810 490

37 120 250 130 0.1 1.1 5.4 1.7 42 130 270 140

23 62 110 64 1.1 16 70 23 30 82 170 89

69 160 350 180 0.1 1.2 5.3 1.7 80 170 370 190

23 62 150 71 2.6 36 180 57 37 110 310 130

400 880 1,600 910 0.0 0.2 0.8 0.2 400 880 1,600 920

81 190 320 200 7.8 110 450 150 130 320 730 360

2,100 4,200 7,500 4,400 13 170 670 240 2,300 4,500 7,900 4,700

4,100 7,100 11,000 7,300 150 580 1,500 670 4,600 7,800 12,000 8,100

Wyoming-Idaho-Utah Thrust Belt (C5036)—Continued

4,400 7,800 12,000 8,000 72 930 3,600 1,300 5,100 9,000 15,000 9,400

5,500 11,000 18,000 11,000 140 1,900 7,600 2,600 6,600 13,000 23,000 14,000

5,700 9,500 14,000 9,600 16 210 790 280 6,000 9,800 15,000 10,000

5,500 9,400 15,000 9,600 4.9 73 290 100 5,600 9,500 15,000 9,700

210 410 690 430 9.8 130 500 180 300 600 1,100 640

190 340 510 350 11 140 530 190 260 500 950 540

45 130 330 150 1.4 19 99 31 56 160 410 190

55 120 210 130 4.7 65 270 92 79 190 440 220

26,000 39,000 55,000 39,000 780 3,800 12,000 4,700 28,000 43,000 63,000 44,000
U.S. Geological Survey Geologic Carbon Dioxide Storage Resources Assessment Team—National Assessment—Results—Circular 1386, ver. 1.1

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