Section 2 

Methodology 

2.0 METHODOLOGY 

The Paradox/San Juan, Uinta/Piceance, Greater Green River, and Powder River basins, and the 

Montana Thrust Belt, compose the five study areas in this inventory. They were delineated by the 

aggregation of oil and/or natural gas resource plays1 in these basins as defined by the USGS 

National Assessment of Oil and Gas Resources. Resource play boundaries and oil and gas 

resource estimates within the plays were obtained in GIS format from the USGS. These plays 

were aggregated in a GIS to create a resource density map layer for each study area. 

Land status was compiled from the “Status” dataset from BLM’s land records database to 

generate GIS maps for the analyses. Oil and gas leasing stipulation data were obtained for each 

jurisdiction from BLM Field Offices and USDA-FS Offices in the study areas. Most of the data 

were available in GIS format; some existed only as hardcopy and had to be digitized to create 

GIS digital map files. 

Stipulations attached to oil and gas leases currently in effect are not maintained in an automated 

system and therefore some existing stipulations may not have been used in this inventory. The 

stipulations used are primarily those contained in the National Forest Plans and BLM Resource 

Management Plans in effect as of the date of this inventory (August 2002), and are those applied 

when new oil and gas leases are issued. To the extent that current leases were issued under, and 

are stipulated according to an existing land use plan, the inventory reflects an accurate situation. 

Older leases issued before the relevant plan's effective date may not be stipulated accordingly. 

To completely characterize stipulations on existing leases, an extensive manual file search would 

have to be performed. However, it is reasonably accurate to consider the plan stipulations as a 

proxy, because the environmental conditions that necessitate stipulations often are the driver for 

conditions of approval that are attached to drilling permits on older leases in order to achieve the 

needed environmental protection. 

The analyses for the EPCA inventory entailed spatial intersection (in a GIS) of oil and gas 

resource information with data on land status and leasing stipulations. Because stipulations are 

conditions that are attached to oil and gas leases for environmental protection and other reasons, 

they are subject to change over time. This inventory represents a "snapshot in time" of the 

conditions present within the study areas. The inventory also takes into account how leasing 

stipulations are implemented in practice by Federal land managers by considering the effect of 

directional drilling and the frequency with which exceptions to the stipulations are granted. 

Additional factors that affect oil and gas exploration and development on Federal lands generally 

cannot be quantified geographically prior to the receipt of a specific drilling application, nor are 

there requisite data available for quantitative analysis. These include: 

ü Protection for threatened and endangered species and surveys to determine whether a lease 

contains habitat for such species; 

1

 A play is a set of known or postulated oil and gas accumulations sharing similar geologic, geographic, or 

temporal properties (source rock, migration pathway, timing, trapping mechanism, hydrocarbon type, etc.). 

For the Paradox and Uinta basins, due to overlapping plays, the EPCA study area boundaries were defined 

by the outline of Uinta plays. The Uinta/Piceance study areas thus contain portions of some Paradox Basin 

plays. 

2-1 
Section 2 

Methodology 

ü Archaeological reviews required by the National Historic Preservation Act, and related issues 

involving cultural resources including consultation with Native American tribes; 

ü Air quality impacts, especially visibility considerations in the Interior West, and resulting 

restrictions on activities that may affect air quality; 

ü Visual impacts of oil and gas operations; 

ü Noise from oil and gas operations; 

ü Conflicts between oil and gas and other mineral operations, such as coal and potash; 

ü Suburban encroachment on oil and gas fields and county government restrictions; 

ü “Sense of Place,” i.e., an emotional or spiritual attachment to certain locations which has 

been used as justification for designating certain areas as off limits to drilling; 

Typically these requirements manifest themselves as conditions of approval attached to drilling 

permits following a specific analysis under the National Environmental Policy Act (NEPA). 

These requirements can delay or modify a planned oil and gas development activity at the permit 

stage and in some cases preclude it altogether. Because these requirements were not easily 

quantifiable, there were not included in this inventory. 

The rest of this section provides a more detailed description of the EPCA inventory methodology. 

2.1 PROCEDURES FOR COLLECTING AND ANALYZING LAND STATUS 

AND LEASE STIPULATIONS 

2.1.1 Land Status 

For the EPCA inventory, all Federal lands2 and split estate3 within the study areas were examined. 

2.1.1.1 Sources of Land Status Data 

Land status carries with it a complex definition involving both ownership and availability of the 

surface and mineral estates. Inherent in a Federal mineral lease is a limited right of surface use in 

order to develop the mineral estate. For the purpose of this inventory, land status refers both to 

Federal ownership of the oil and gas mineral estate and to the availability of the Federal mineral 

estate for oil and gas leasing. 

The source of Federal land status data is the BLM’s Land Status Database. These data, which are 

stored in alphanumeric format, were converted for this inventory into a GIS layer by using 

commercially available software. The software interpolated the legal descriptions contained in 

the Status Database against a public land survey GIS layer derived from either the BLM’s 

Geographic Coordinate Database (GCDB) or other sources such as digitized USGS 7-1/2 minute 

quadrangle maps. 

2.1.1.2 Land Status Data Preparation 

Maps of the Federal land status for the study areas are presented in figures 2a through 2e. See 

Appendix 3 for a more detailed description of land status data preparation. 

2

 Indian lands were not included in this inventory.

3 Federal split estate resources are subject to the same Federal restrictions as those implemented on Federal

lands because access to these resources through leasing and permitting is a Federal action.

2-2 
Section 2

Methodology

Figure 2a Federal Land Status Map -- Paradox/San Juan Study Area 

2-3
Section 2

Methodology

Figure 2b Federal Land Status Map – Uinta/Piceance Study Area 

2-4 
Methodology

Section 2

Figure 2c Federal Land Status Map – Greater Green River Study Area 

2-5 
Methodology

Section 2

Figure 2d Federal Land Status Map – Powder River Study Area 

2-6 
Section 2

Methodology

Figure 2e Federal Land Status Map – Montana Thrust Belt Study Area 

2-7 
Section 2 

Methodology 

2.1.1.3 Land Status Data-Related Caveats 

The land status data are spatially accurate down to 40 acres. The BLM considers this information 

complete and up to date as of August 2002. 

The GIS files created using the processes described in Appendix 3 were interpolated from the 

legal land descriptions contained in BLM’s Land Record database. If a legal description 

referenced a small survey lot or tract by number, a nominal location was mapped through a 

process that referenced the Legal Land Description dataset. This dataset is limited to a 40-acre 

description and therefore carries a minor degree of generalization in complex areas. 

This mapping process uses public land survey data derived from various sources. The spatial 

location of the land status parcels so derived matches the accuracy of the survey data. 

2.1.2 Lease Stipulations 

All Federal onshore oil and gas leases contain terms and conditions specified in the standard 

Federal lease form. Some of these terms and conditions govern land use and resource 

development to a certain extent. Environmental and other considerations, which are identified 

during the land use planning process, determine the need for additional terms and conditions, also 

known as stipulations. For example, a lease may contain a stipulation that prohibits surface 

disturbance where land slopes exceed 35 percent. These stipulations may represent constraints to 

the exploration for and development of oil and natural gas on Federal lands. 

2.1.2.1 Sources of Lease Stipulation Data 

Oil and gas lease stipulations are derived from the surface management agency’s land use plans. 

The BLM’s planning documents are referred to as Resource Management Plans (RMPs); the 

USDA-Forest Service’s are referred to as Forest Plans. These plans are produced and generally 

maintained by their respective agencies on a Field Office jurisdictional basis (in the case of the 

BLM), or on a National Forest/Grassland basis (in the case of the USDA-FS). 

Most of the lease stipulation data are maintained by the agencies as GIS data layers (digital map 

files). Some offices, particularly where the planning effort pre-dated the widespread availability 

of GIS technology, still maintain this information in the form of hardcopy maps. These maps 

were digitized, stored, and analyzed as GIS layers for this inventory. 

Hard copy and digital data showing the mapped lease stipulation areas were collected from BLM 

and Forest Service offices within the study areas (listed in Table 1a). Copies of guidance 

documents, such as RMPs and Forest Plans, were also obtained. Appendix 8 lists the guidance 

documents used in this inventory, and Appendix 9 (available on CD-ROM or website only) lists 

the actual stipulations themselves. 

For the Paradox/San Juan, Powder River, and Montana Thrust Belt study areas, data were 

collected in the winter of 2001-2002. For the Uinta/Piceance study area, data were collected in 

the fall of 2001. For the Greater Green River (GGR) study area, data were used from the DOE’s 

2-8 
Section 2 

Methodology 

Federal lands analysis10 collected during the fall and winter of 2000-2001; these data were 

verified with the local BLM and USDA-FS offices and are current as of August 2002. 

2.1.2.2 Lease Stipulation Data Preparation 

The bulk of the data preparation consisted of the gathering, digitizing, and compiling of the 

gathered data in multi-layered digital map files. Federal Geographic Data Committee Standards 

(FGDC)-compliant supporting documentation (metadata) for the resulting GIS layers were also 

created11. 

This inventory is limited to those Federal lands within the aggregate resource play boundaries of 

the five study areas, which are based on geology as defined in the USGS National Assessment of 

Oil and Gas Resources. The land status and stipulation digital map files, which corresponded to 

Federal land management agency jurisdiction boundaries, were cut to fit within each of the study 

area boundaries using the GIS. Data contained within the compiled digital map files were then 

queried for unique leasing stipulation values. The results were then saved as separate map files. 

Each digital map file represents a unique stipulation value. 

For an example of the specific data preparation steps, see Appendix 4. 

2.1.2.3 Lease Stipulation Data-Related Caveats 

All stipulations for which GIS data were available from the Federal land management agencies 

were used in the analysis. A majority of the stipulations within the study areas were available in 

GIS data formats. However, supporting documentation was not generally provided with GIS 

files. This can lead to inaccuracies due to undocumented differences in technical parameters. 

Any such errors are minor in terms of the scope of the inventory. 

Stipulations not available in GIS format were digitized and any resulting inaccuracies have only 

minor effects upon the analysis. 

In a few cases neither hardcopy nor digital maps were available for certain stipulations. The 

result is that the ensuing analyses may underestimate the extent of restrictions on land access. 

This occurred for less than 10 percent of the stipulations. 

The lease stipulation data are generally accurate to 40 acres. The information is considered 

complete and up to date as of August 2002. 

10 Federal Lands Analysis, Natural Gas Assessment, Southern Wyoming and Northwestern Colorado, Study

Methodology and Results, June 2001, available on the DOE website:

http://fossil.energy.gov/techline/tl_ggrb_gas.shtml. 11 GIS layers from surface management agency land status, stipulations, and the analyses, as well as the

associated metadata, are available on the CD-ROMs and the web sites.

2-9 
Section 2 

Methodology 

2.2 PROCEDURES FOR COLLECTING AND ANALYZING OIL AND GAS 

RESOURCE DATA 

2.2.1 Sources of Oil and Gas Resource Data 

In conformance with EPCA, the volumes of undiscovered technically recoverable oil and gas 

resources in each oil and gas play are supplied exclusively by the USGS. 

The In-place resource 

to-be discovered) without regard to the ability to either access or produce it. Although the in-place 

continually changing as technology improves. 

Technically recoverable resources are a subset of the in-place resource that includes only that oil 

and gas (both discovered and undiscovered) that is expected to be producible given available 

technology with no regard to current costs. Technically-recoverable resources are therefore 

dynamic, constantly changing to reflect our increased understanding of both the in-place 

resource as well as the likely nature of future technology. 

Economically recoverable resources

that oil and gas that is expected to be producible at a profit. This is a very dynamic category, 

changing not only with increasing knowledge and technology, but also with the rapid and 

sometimes unpredictable changes in economic conditions, prices, and regulation. 

Reserves

production. Reserves are also subject to economic conditions. 

Oil and gas resources occur in four categories: 

is the total volume of oil and gas thought to exist (both discovered and yetresource is primarily a fixed, unchanging volume, the current understanding of that volume is 

 are a subset of the technically recoverable that includes only 

 are oil and gas that has been proven by drilling and is available for profitable 

Technically recoverable resources are those hydrocarbon resources that, on the basis of geologic 

information and theory, are estimated to exist outside of known producing fields. This class of 

hydrocarbon resources is that which can be produced using current technology but without regard 

to economic profitability. Technically recoverable resources are the subset of resources-in-place 

that could be expected to be recovered over an exploration and development life cycle measured 

in decades. 

An economic analysis of the undiscovered technically recoverable resources would require a 

number of assumptions about future costs of exploration and development, transportation and 

infrastructure that can change significantly with time. Such an analysis is a subjective exercise, 

and is not appropriate for Federal land use decisions or allocation. An economic analysis on a 

project-specific basis is most appropriate when used by the private sector in its decision making 

process. 

The resources included in this study comprise oil, natural gas liquids (NGLs), associated 

dissolved (AD) natural gas, non-associated (NA) natural gas and liquids in gas reservoirs. Oil is a 

natural liquid of mostly hydrocarbon molecules. NGLs are liquid when produced to the surface 

but exist in the gas phase in the subsurface. Natural gas is a mixture of hydrocarbon gases 

consisting primarily of methane. Associated dissolved natural gas is that produced from oil 

fields, whereas non-associated natural gas is that produced "dry” from gas fields. The USGS 

assesses technically recoverable resources for each of these resource types, and those volumes 

were provided for this effort. However, for this inventory, undiscovered oil, NGL, and liquids 

2-10 
Section 2 

Methodology 

associated with natural gas reservoirs were subsequently merged into a single “Total Liquids” 

resource category (table 2a). 

The USGS uses the resource "play" as the unit of assessment. A play is defined by a set of 

common geological conditions (source rock, migration, charge, traps, seals, etc.) that characterize 

a group of hydrocarbon accumulations in the subsurface. The USGS specifically states in the 

assessment process that resource volumes are not homogeneously distributed within a play. 

However, a homogeneous distribution of resource within a play boundary is assumed for the GIS 

analysis in this inventory in the absence of more specific information. Nonetheless, variation in 

the vertical sense is captured by the use of play stacking. The geometry of a resource play is 

defined by geological environments and has horizontal and vertical expression. The areal extent 

of resource plays is represented in map view (figure 2f) by vertically projecting their subsurface 

locations to the surface. In cross-section, the relative depths of individual plays are represented in 

figure 2g. The plays are commonly "stacked" in the subsurface so that a given surface land parcel 

can overlie numerous plays. 

X X’

Cross -section Play Area

#1 

#2 

#3 

X X’

Cross-section Play Area

#1

#2

#3

X X’

Cross-section Play Areas

#1

#2

#3

Figure 2f Map View of Resource Plays 

2-11 
Section 2 

Methodology 

Surface Level

X’ X

Increasing Play 3 Subsurface

Depth

Play 2

Play 1

X X’ Line of Cross-section View From Map View of Play Area

Figure 2g Cross Section of Resource Plays 

In this inventory, there are two resource play types: conventional and continuous 

(unconventional, which includes coalbed gas). Conventional plays contain discrete hydrocarbon 

accumulations often associated with hydrocarbon/water contacts. Continuous plays exist as 

pervasive accumulations that can cross rock unit boundaries, lack discrete borders and exhibit 

other atypical reservoir properties (figure 2h). The majority of the resources in the study areas 

are continuous in nature. Compared to conventional plays, continuous accumulations typically 

are more geographically extensive. 

Coalbed methane (CBM), also known as coalbed natural gas, is natural gas from coal beds and is 

one form of continuous play. Coalbed natural gas resources are the second largest resource 

component in this inventory. 

2-12 
Section 2 

Methodology 

Figure 2h. Conventional vs. Continuous Accumulations 

2.2.2 Oil and Gas Resource Data Preparation 

The USGS identified eighty-eight discrete plays of oil and natural gas resources in the EPCA 

inventory areas. The mean probabilistic estimates of hydrocarbon resource volumes for each 

USGS-defined play were utilized for this inventory (Table 2a). 

For this inventory, an important simplifying assumption was made that the oil and gas resources 

are evenly distributed within each resource play area. Therefore, resource volume is calculated to 

be proportional to surface area within each play. A resource density map for each basin was 

created in the GIS by a spatial summation of the oil and gas volumes contributed by each 

resource play. The densities are expressed as thousand cubic feet (MCF) of gas per acre and 

barrels (BBL) of oil per acre. 

The products of the oil and gas resource data preparation work are maps of hydrocarbon volumes, 

projected to the surface. These maps depict areas of varying potential resource richness based on 

play resource volumes and play stacking. The distributions of undiscovered technically 

recoverable resources are shown by study area for liquids in figures 2i through 2m and for gas in 

figures 2n through 2r. See Appendix 5 for a more detailed description of the USGS methodology 

for the assessment and allocation of undiscovered oil and gas resources. 

2-13 
Section 2 

Methodology 

USGS 

Province 

Name 

Paradox Basin 

Paradox Basin 

Paradox Basin 

Paradox Basin 

Paradox Basin 

Paradox Basin 

Paradox Basin 

San Juan Basin 

San Juan Basin 

San Juan Basin 

San Juan Basin 

San Juan Basin 

San Juan Basin 

San Juan Basin 

San Juan Basin 

San Juan Basin 

San Juan Basin 

San Juan Basin 

San Juan Basin 

San Juan Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Uinta - Piceance Basin 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Southwestern Wyoming 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Powder River Basin 

Montana Thrust Belt 

Montana Thrust Belt 

Montana Thrust Belt 

Montana Thrust Belt 

Montana Thrust Belt 

Montana Thrust Belt 

Montana Thrust Belt 

Totals 

USGS USGS 

Code Play or Assessment Unit Name 

2101 Buried Fault Blocks, Older Paleozoic 

2102 Porous Carbonate Buildup 

2103 Fractured Interbed 

2104 Permian-Pennsylvanian Marginal Clastics 

2105 Salt Anticline Flank 

2106 Permo-Triassic Unconformity 

2107 Cretaceous Sandstone 

50220101 Tertiary Conventional Gas 

50220161 Pictured Cliffs Continuous Gas 

50220181 Fruitland Fairway Coalbed Gas 

50220182 Basin Fruitland Coalbed Gas 

50220261 Lewis Continuous Gas 

50220302 Gallup Sandstone Conventional Oil and Gas 

50220303 Mancos Sandstones Conventional Oil 

50220304 Dakota-Greenhorn Conventional Oil and Gas 

50220361 Mesaverde Central-Basin Continuous Gas 

50220362 Mancos Sandstones Continuous Gas 

50220363 Dakota-Greenhorn Continuous Gas 

50220381 Menefee Coalbed Gas 

50220401 Entrada Sandstone Conventional Oil 

50200101 Conventional Ferron Sandstone Gas 

50200161 Deep (6,000 feet plus) Coal and Sandstone Gas 

50200181 Northern Coal Fairway/Drunkards Wash 

50200182 Central Coal Fairway/Buzzards Bench 

50200183 Southern Coal Fairway 

50200184 Joes Valley and Messina Grabens 

50200185 Southern Coal Outcrop 

50200201 Uinta-Piceance Basin Conventional Gas 

50200261 Uinta Basin Continuous Gas Mesaverde TPS 

50200262 Uinta Basin Transitional Gas 

50200263 Piceance Basin Continuous Gas Mesaverde TPS 

50200264 Piceance Basin Transitional Gas 

50200281 Uinta Basin Blackhawk Coalbed Gas 

50200282 Mesaverde Group Coalbed Gas 

50200361 Piceance Basin Continuous Gas Mancos/Mowry TPS 

50200362 Uinta Basin Continuous Gas Mancos/Mowry TPS 

50200363 Uinta-Piceance Transitional and Migrated Gas 

50200401 Hanging Wall 

50200402 Paleozoic/Mesozoic 

50200501 Uinta Green River Conventional Oil and Gas 

50200502 Piceance Green River Conventional Oil 

50200561 Deep Uinta Overpressured Continuous Oil 

50370101 Sub-Cretaceous Conventional Oil and Gas 

50370201 Mowry Conventional Oil and Gas 

50370401 Hilliard-Baxter-Mancos Conventional O&G 

50370501 Mesaverde Conventional Oil and Gas 

50370601 Mesaverde-Lance-Fort Union Conventional O&G 

50370701 Lewis Conventional Oil and Gas 

50370801 Lance-Fort Union Conventional Oil and Gas 

50370361 Niobrara Continuous Oil 

50370261 Mowry Continuous Gas 

50370461 Hilliard-Baxter-Mancos Continuous Gas 

50370561 Almond Continuous Gas 

50370562 Rock Springs-Ericson Continuous Gas 

50370661 Mesaverde-Lance-Fort Union Continuous Gas 

50370761 Lewis Continuous Gas 

50370861 Lance-Fort Union Continuous Gas 

50370581 Mesaverde Coalbed Gas 

50370681 Mesaverde Coalbed Gas 

50370682 Fort Union Coalbed Gas 

50370881 Lance Coalbed Gas 

50370882 Fort Union Coalbed Gas 

50370981 Wasatch-Green River Coalbed Gas 

3301 Basin Margin Subthrust 

3302 Basin Margin Anticline 

3303 Leo Sandstone 

3304 Upper Minnelusa Sandstone 

3305 Lakota Sandstone 

3306 Fall River Sandstone 

3307 Muddy Sandstone 

3309 Deep Frontier Sandstone 

3310 Turner Sandstone 

3312 Sussex-Shannon Sandstone 

3313 Mesaverde-Lewis 

50330101 E. Basin Margin Upper Fort Union Sandstone 

50330181 Wasatch Formation 

50330182 Upper Fort Union Formation 

50330183 Lower Fort Union-Lance Formations 

50330261 Mowry Continuous Oil Assessment Unit 

50330361 Niobrara Continuous Oil Assessment Unit 

50330461 Shallow Continuous Biogenic Gas AU 

50270101 Thrust Belt Conventional Gas and Oil 

50270102 Sawtooth Range Structure Conventional O&G 

50270103 Frontal Structures Conventional Oil and Gas 

50270201 Helena Salient Conventional Oil and Gas 

50270401 Blacktail Salient Conventional Oil and Gas 

50270561 Marias River Shale Continuous Oil 

50270701 Tertiary Basins Oil and Gas 

Play 

Type 

Conventional 

Conventional 

Continuous 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Continuous Gas 

Coalbed Gas 

Coalbed Gas 

Continuous Gas 

Conventional 

Conventional 

Conventional 

Continuous Gas 

Continuous Gas 

Continuous Gas 

Coalbed Gas 

Conventional 

Conventional 

Continuous Gas 

Coalbed Gas 

Coalbed Gas 

Coalbed Gas 

Coalbed Gas 

Coalbed Gas 

Conventional 

Continuous Gas 

Continuous Gas 

Continuous Gas 

Continuous Gas 

Coalbed Gas 

Coalbed Gas 

Continuous Gas 

Continuous Gas 

Continuous Gas 

Conventional 

Conventional 

Conventional 

Conventional 

Continuous Oil 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Continuous Oil 

Continuous Gas 

Continuous Gas 

Continuous Gas 

Continuous Gas 

Continuous Gas 

Continuous Gas 

Continuous Gas 

Coalbed Gas 

Coalbed Gas 

Coalbed Gas 

Coalbed Gas 

Coalbed Gas 

Coalbed Gas 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Coalbed Gas 

Coalbed Gas 

Coalbed Gas 

Continuous Oil 

Continuous Oil 

Continuous Gas 

Conventional 

Conventional 

Conventional 

Conventional 

Conventional 

Continuous Oil 

Conventional 

Total 

Liquids** 

(MMBbl) 

62 

192 

242 

3 

20 

21 

1 

17 

31 

2 

14 

3 

5 

76 

16 

3 

<.5 

1 

11 

2 

9 

1 

2 

6 

2 

5 

8 

11 

NA 

43 

58 

12 

1 

3 

17 

8 

2 

107 

171 

752 

200 

146 

614 

541 

76 

21 

7 

81 

522 

55 

200 

88 

58 

25 

72 

62 

209 

240 

134 

18 

68 

15 

6 

33 

73 

5,510 

Total 

Natural Gas*** 

(Bcf) 

292 

482 

194 

56 

396 

2 

58 

80 

5,640 

3,981 

19,595 

10,177 

<.5 

58 

22 

1,317 

5,116 

3,929 

664 

6 

40 

59 

752 

537 

153 

NA 

11 

66 

7,391 

1,493 

3,064 

302 

499 

368 

1,653 

3,111 

1,755 

28 

50 

29 

64 

1,383 

206 

15 

56 

320 

195 

246 

62 

8,543 

11,753 

13,350 

12,178 

13,635 

13,536 

7,583 

249 

27 

81 

165 

943 

65 

20 

4 

5 

31 

22 

115 

449 

193 

32 

54 

58 

27 

1,934 

12,132 

198 

198 

227 

787 

5,761 

795 

1,192 

639 

16 

111 

124 

183,204 

* All values are mean resource values from the USGS National Assessment of Oil and Gas Resources (assessment unit resources from the 2002 Update; play resources from the 

NA -- not assessed 

2-14 Table 2a Undiscovered Technically Recoverable Resources by Play 
Section 2

Methodology

Figure 2i Total Liquids Map – Paradox/San Juan Study Area 

2-15 
Section 2

Methodology

Figure 2j Total Liquids Map – Uinta/Piceance Study Area 

2-16 
Section 2

Methodology

Figure 2k Total Liquids Map – Greater Green River Study Area 

2-17 
Section 2

Methodology

Figure 2l Total Liquids Map – Powder River Study Area 

2-18
Section 2

Methodology

Figure 2m Total Liquids Map – Montana Thrust Belt Study Area 

2-19 
Section 2

Methodology

Figure 2n Total Gas Map – Paradox/San Juan Study Area 

2-20 
Section 2

Methodology

Figure 2o Total Gas Map – Uinta/Piceance Study Area 

2-21 
Section 2

Methodology

Figure 2p Total Gas Map – Greater Green River Study Area 

2-22
Section 2

Methodology

Figure 2q Total Gas Map – Powder River Study Area 

2-23 
Section 2

Methodology

Figure 2r Total Gas Map – Montana Thrust Belt Study Area 

2-24
Section 2 

Methodology 

2.2.3 Oil and Gas Resource Data-Related Caveats 

The estimation of technically recoverable resources is inherently uncertain, as reflected by the 

fact that the USGS develops cumulative probability distributions for the resource estimates of all 

of its plays. These distributions are used to derive 95 percent probable (a 19-in-20 chance of that 

volume or more), 5 percent probable (a 1-in-20 chance of that much or more) and mean resource 

volumes. The mean volume, used in this inventory, represents the arithmetic average of all 

possible resource outcomes weighted by their probability of occurrence. Therefore, the analytical 

results shown here do not explicitly reflect the range of uncertainty in the resource assessments. 

In addition, not all of the resource plays recognized by the USGS within the boundaries of this 

inventory have been evaluated, typically because there are hypothetical plays that lack sufficient 

supporting data to calculate resource estimates. To the extent that these plays contain significant 

volumes of resources, the results presented here would be different relative to a larger resource 

base. 

Given these considerations, it should be understood that no resource assessments are set in stone. 

Not only is it difficult to accurately assess the resource at any one point in time, but the resource 

itself is constantly changing in response to the advance of technology and the evolving economic 

and policy conditions under which extraction is likely to occur. Nonetheless, it is of vital 

importance that accurate and up-to-date assessments of the potential resources are continually 

provided to ensure that public policy decisions are conducted with the most timely information 

possible. 

2.3 PROCEDURES FOR COLLECTING AND ANALYZING PROVED OIL 

AND GAS RESERVES DATA 

The EPCA Section 604 responsibility of the Energy Information Administration is to provide data 

and analysis relevant to proved reserves of crude oil, natural gas, and natural gas liquids which 

are associated with already discovered fields that underlie Federal onshore lands. This 

responsibility involves: 

• provision of estimates of proved reserves for these fields at the highest possible level of detail 

consonant with a legal requirement to protect the confidentiality of field operators' 

proprietary estimates of proved reserves, 

• estimation of future ultimate recovery appreciation for currently producing fields, and 

• provision of inputs to the estimation of additional land access requirements that may be 

consequent to the expected ultimate recovery appreciation. 

Proved reserves are defined as those quantities of crude oil, natural gas, or natural gas liquids that 

geological and engineering data demonstrate with reasonable certainty (defined as 90 percent or 

more probable) to be recoverable in future years from known reservoirs under existing economic 

and operating conditions. Proved reserves are, in effect, the current “inventory on-the-shelf" 

portion of the total resource endowment.4 

4 The full technical definition of proved reserves is available on the Society of Petroleum Engineers website at 

http://www.spe.org/spe/cda/views/shared/viewChannelsMaster/0,2883,1648_19738_19746_24741,00.html 

2-25 
Section 2 

Methodology 

Estimates of future ultimate recovery appreciation (URA), sometimes referred to as “reserves 

growth” are not included as a part of this analysis. The URA estimate will be provided as part of 

a future revision to this inventory. 

2.3.1 Sources and Data-Related Caveats of Proved Oil and Gas Reserves 

Data 

Comprehensive deterministic estimates of the domestic proved reserves of crude oil, natural gas, 

and natural gas liquids are prepared annually by the EIA. These estimates are a combination of 

reported and statistically imputed volumes based on: 

• thousands of individual proved reserves and production estimates reported annually either at 

the field level or at the State level as described below, submitted to EIA by a statistical 

sample of the operators of domestic oil and gas wells on Form EIA-23 “Annual Survey of 

Domestic Oil and Gas Reserves.” Of the 22,519 operators in the 2001 survey, 1,867 were 

included in the sample. 

• all operators of active domestic natural gas processing plants who annually report their 

operations on Form EIA-64A “Annual Report of the Origin of Natural Gas Liquids 

Production.” For the 2001 survey, there were 525 active plants, all of which responded. 

Only the largest oil and gas well operators (those producing 1.5 million barrels or more of crude 

oil or 15 billion cubic feet or more of natural gas, or both) are required to maintain and submit to 

EIA both proved reserves and production estimates by field for all of their operated properties. 

There were 172 large operators in the 2001 survey, all of which were included in the sample. 

Their response rate was 100 percent. 

Intermediate size operators (those producing less than the largest operators but at least 400,000 

barrels of crude oil, or at least 2 billion cubic feet or natural gas, or both) are required to submit 

production estimates by field for all of their operated properties, but are only required to submit 

proved reserves estimates by field when they maintain them in their records. There were 439 

mid-sized operators in the 2001 survey. All were included in the sample and their response rate 

was also 100 percent. 

Small operators are those with production less than the other limits. There were 21,908 small 

operators in the 2001 survey. Of these, 1,175 were sampled with certainty at an associated 

response rate of 98 percent and an additional 622 were randomly sampled at an associated 

response rate of 95 percent. 

Because the EIA reserves survey is expressly designed to minimize the respondents’ reporting 

burden and yet provide highly reliable estimates at the State and National levels of data 

aggregation, the EIA does not have in its files operator-submitted, field-specific proved reserves 

information covering every oil or gas field in the country. For example: 

• The EIA may have only partial reported proved reserves estimates for a field that has two or 

more operators, at least one of which is not required to report proved reserves by field. 

• Especially for small fields, the EIA may not have any reported proved reserves estimates. 

2-26 
Section 2 

Methodology 

However, because the large and intermediate size operators tend to operate the larger fields, 

whereas the small operators are primarily active in the far more numerous small fields, the EIA 

does have in its files field-specific, operator-submitted proved reserves estimates covering about 

90 percent of all estimated domestic proved reserves. 

These types of deficiencies in the EIA’s field-specific reserves information were satisfactorily 

remedied for this inventory by use of additional procedures based on either publicly available 

production data or reserve-to-production ratio analogs. The procedures used are detailed in 

Appendix 6. 

Beyond the necessity to develop complete proved reserves estimates when complete operatorsubmitted estimates were lacking, there were two additional limitations: 

(1) As collected in the EIA reserves survey, field location is at the county level. Attainment of 

the much more precise field locations required for this inventory's GIS-based methodology 

necessitated cross-correlation of the EIA’s reserves data files with commercial sources of field 

and/or well information which provide far more precise field location data. This process involved 

much highly detailed, often well-by-well, work owing to the existence of non-standard field 

names and codes, or the occasional lack of a field name, in the commercial data sources. 

(2) EIA is obligated by law to ensure the confidentiality of the data submitted by each reserves 

survey respondent. Within the EPCA study areas, there were many situations where a field was 

operated by a single operator or where one operator was heavily dominant. In such instances, 

EIA cannot disclose the proved reserves estimates for the field in absence of a written agreement 

in which the operator waives its right to confidentiality. Such agreements are exceedingly rare. 

Therefore, to avoid the release of confidential information while still adequately informing this 

inventory, EIA elected not to present field-specific proved reserves estimates even in instances 

where doing so would not have compromised a respondent's submission. Instead, the fields have 

uniformly been classified into a range of proved reserves categories that are broad enough to 

prevent extraction of the proved reserves estimates for any specific field. The resulting summary 

of proved reserves is shown in table 2b. 

The proved oil and gas reserves are not mapped as are the undiscovered technically recoverable 

resources in figures 2i through 2r and figures 3l through 3ad. However, the reserves figures, 

presented in table 2b, are included in the summary tables and pie charts (table ES-1, figure ES-2, 

tables 3a through 3f and figures 3a through 3f). Proved reserves are included in the “Leasing, 

Standard Lease Terms (SLT)” category since by definition they are accessible with minimal 

constraints. 

See Appendix 6 for a more detailed explanation of proved reserves estimation and field boundary 

construction. 

2-27 
Section 2 

Methodology 

Basin 

Number 

of 

Fields 

Total 

Liquid 

Reserves 

(Mbbl) 

Federal 

Land 

Liquid 

Reserves 

(Mbbl) 

% 

Federal 

Total 

Gas 

Reserves 

(MMcf) 

Federal 

Land 

Gas 

Reserves 

(MMcf) 

% 

Federal 

Total 

BOE* 

Reserves 

(Mbbl) 

Federal 

Land 

BOE 

Reserves 

(Mbbl) 

% 

Federal 

Paradox-San Juan 250 174,193 53,103 30.5 20,653,622 11,033,357 53.4 3,616,464 1,891,996 52.3 

Uinta-Piceance 180 254,329 142,495 56.0 7,181,669 3,779,755 52.6 1,451,274 772,454 53.2 

Greater Green River 281 177,362 122,234 68.9 12,703,038 10,081,667 79.4 2,294,535 1,802,512 78.6 

Powder River 543 193,456 110,783 57.3 2,398,604 927,738 38.7 593,223 265,406 44.7 

Montana Thrust Belt 1 1 0 0.0 0 0 0.0 1 0 0.0 

Total 1,255 799,341 428,616 53.6 42,936,933 25,822,517 60.1 7,955,497 4,732,368 59.5 

*Barrels of Oil Equivalent

 Table 2b Proved Reserves Summary Statistics, 2001 

2.4 DATA INTEGRATION AND SPATIAL ANALYSIS 

Data integration and spatial analysis were performed as described below. The 

assumptions that were made as a part of the modeling process are described and 

the spatial analysis performed in the GIS are described in Appendix 7. 

2.4.1 Categorization for Federal Land Status and Lease Stipulations

Two factors affect access to oil and gas resources on Federal lands: land status (Section 2.1.1) 

and leasing stipulations (Section 2.1.2). To simplify the analysis and present meaningful results, 

these two factors were combined into a hierarchy of categories that represents varying levels of 

access as shown in table 2c. This categorization was necessary to enable a reasonable 

quantitative analysis given the fact that approximately 1,000 unique stipulations exist within the 

study areas. 

More 

Constrained 

Level

Access Category Comments 

1. No Leasing (Statutory/Executive Order), (NLS) Status set by Law or Executive Order; drilling prohibited 

2. No Leasing (Administrative), Pending Land Use Planning or NEPA 

Compliance (NLA/LUP) 

Status set by Federal surface management agency; 

drilling prohibited 

3. No Leasing (Administrative), general category (NLA) 

4. Leasing, No Surface Occupancy (NSO) Directional drilling permitted from off-lease locations* 

5. Leasing, Cumulative Timing Limitations on Drilling >9 Months (TLs >9) Categorized by the cumulative effect of seasonal 

leasing stipulations during which drilling is prohibited, 

generally for protection of wildlife 

6. Leasing, Cumulative Timing Limitations on Drilling 6-9 Months (TLs 6-9) 

7. Leasing, Cumulative Timing Limitations on Drilling 3-6 Months (TLs 3-6) 

8. Leasing, Cumulative Timing Limitations on Drilling <3 Months (TLs <3) 

9. Leasing, Controlled Surface Use (CSU) Drilling permitted, specialized mitigation plan required 

10. Leasing, Standard Lease Terms (SLTs) Drilling permitted, mitigation plan required 

Less *Resources under margins of NSO areas may be accessible by directional drilling. 

Constrained 

Table 2c Categorization Hierarchy 

The hierarchy of categories was formulated to ensure that the potential for oil and gas 

development could be appropriately assessed (especially for areas of multiple, overlapping 

stipulations), and to ensure that the cumulative impacts on access would be examined. In 

addition, the hierarchy was formulated based upon the accessibility of the lands for leasing, for 

areas in which leasing is permitted, and the impacts relative to the costs to operators for 

conducting drilling. 

The categorization is ordered from No Leasing to Leasing with Standard Lease Terms as follows: 

2-28 
Section 2 

Methodology 

1. No Leasing (Statutory/Executive Order) (NLS) are areas that cannot be leased 

due to Congressional or Presidential action. Examples include national parks, 

national monuments, and wilderness areas. 

2. No Leasing (Administrative) Pending Land Use Planning or NEPA 

Compliance (NLA/LUP) are Federal administrative areas that are currently 

undergoing land use planning or NEPA analysis and are not currently available 

for leasing.5 Table A7-1 in Appendix 7 shows the NLA/LUP jurisdictions within 

the EPCA inventory area. 

3. No Leasing (Administrative) (NLA) are areas in which leasing does not occur 

based on discretionary decisions made by the Federal land management agency. 

NLAs include endangered species habitat and historical sites. 

4. Leasing, No Surface Occupancy (NSO) are areas that can be leased but 

stipulations generally prohibit surface occupancy for natural gas and oil 

exploration and development activities to protect identified resources such as 

special status plant species habitat. NSO areas are treated in the analysis as no 

access areas (administrative); however, these areas can be accessed by directional 

drilling as described later in this document. 

5-8. Leasing, Cumulative Timing Limitations (TLs) are areas that can be leased, 

but stipulations limit the time of the year when oil and gas exploration and 

drilling can take place. Timing limitation stipulations prohibit surface use during 

specified time intervals to protect identified resources such as sage grouse habitat 

or elk calving areas. 

9. Leasing, Controlled Surface Use (CSU) are areas that can be leased, but 

stipulations control the surface location of natural gas and oil exploration and 

development activities by excluding them from certain portions of the lease. For 

example, a CSU stipulation could require an operator to develop a specialized 

mitigation plan based on the presence of steep slopes within a lease area. 

10. Leasing, Standard Lease Terms (SLT) are areas that can be leased, and where 

no additional stipulations are added to the standard lease form. Standard lease 

terms, however, still dictate that the lessee comply with a number of 

environmentally protective and other requirements. 

Appendix 9 (available on the CD-ROMs or the web sites) provides a listing and coding of the 

individual stipulations for each of the study areas. 

2.4.2 Analytical Modeling of Federal Lands and Resources 

See Appendix 7 for a detailed description of the GIS methodology used to categorize the Federal 

lands and resources for the inventory. 

5

 This category was determined on a case-by-case basis as the initiation of a new land use plan or plan 

revision does not generally preclude leasing under an existing plan. 

2-29