James A. Luppens1 , Timothy J. Rohrbacher2, Jon E. Haacke2, 

David C. Scott2, and Lee M. Osmonson2

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

Status Report: USGS Coal Assessm

of the Powder River Basin, Wyom

U.S. Geological Survey Open-File Report 2006-1072

This report is preliminary and has not been reviewed for conformity

with U.S. Geological Survey editorial standards and stratigraphic

nomenclature. Any use of trade names is for descriptive purposes

only and does not imply endorsement by the U.S.G.S.

Available on the Internet at http://infotrek.er.usgs.gov/pubs/

Figure 1. Title Slide: “Status Report: USGS Coal Assessment Status Report: USGS Coal Assessment of the Powder of the Powder River, Wyoming” by Jam

by J. Rohrbacher, Jon E. Haacke, David C. Scott, and Lee M. Osmonson; U.S. Department of the Inter

Survey.
USGS Coal Program

3⁄4 Current and future coal assessments 

just another in-place coal resource number.

3⁄4 Regional estimates of economically 

recoverable coal will be an integral pcurrent and future assessments.

3⁄4 How much economically recoverable 

do we have left?

Figure 2. Objectives of the current and future USGS coal assessment programs. An inventory of teconomically recoverable coal provides a better foundation for energy planning than simply relying 

resources.
Importance of Coal Importance of Coal

Assessment Project Assessment Project

3⁄4 National energy reliance and energy National energy reliance and energ

policy 

3⁄4 Regional energy and economic Regional energy and economic 

planning planning

3⁄4 Federal lands inventory Federal lands inventory3⁄4 Coal bed methane (CBM) exploratio

Coal bed methane (CBM) exploratio

and development and development

3⁄4 Carbon sequestration Carbon sequestration

Figure 3. Importance of USGS coal assessment project to energy policy and research.
Current and Future Coal Assessment W

Where do we go from here?

3⁄4 Reserve investigations require more up front geo

Reserve investigations require more up front geo

and engineering work. and engineering work.

3⁄4 However, new, highly automated regional mine However, new, highly automated regional mine modeling and economic programs developed by 

modeling and economic programs developed by 

USGS facilitate the reserves evaluation. USGS facilitate the reserves evaluation.

3⁄4 The USGS assessment methodology was formally The USGS assessment methodology was formally evaluated by an external review panel with an op

evaluated by an external review panel with an o

report published in February, 2005 Rohrbacher, T

report published in February, 2005 Rohrbacher, 

and others, 2005 (http://pubs.usgs.gov/of/2005/

and others, 2005 (

3⁄4 Builds on the digital geolog Builds on the digital geologic framework of past 

ic framework of past 

resource assessments. resource assessments.

3⁄4 Started next coal assessment phase in the greate

Started next coal assessment phase in the greate

Powder River Basin (PRB) in FY2005. Powder River Basin (PRB) in FY2005.

Figure 4. The direction of current and future USGS coal assessments.
Regional Coal Resource Evaluation Overv

Regional Coal Resource Evaluation Overv

Data Collection

Coal bed geology (extent, thickness partings, structure, overburden, etc.)Factors affecting extraction (land-use and technical restrictions)Location of preparation plants, roads, and rail facilitiesState and county jurisdictions and resource ownership

Mining and haulage assumptionsMine production and cost data

Coal quality informationRecent coal sales price(s)Tax information

GIS (ArcView)

Create or import grids / manipulate gridsCalculate tonnages and areas for original, mined 

out, restricted, and available resources

Create or modify mine models for each study areaAllocate available resources to mine models

CoalVal

Import available resources by mine model, all costs, and Calculate recoverable tonnages and mining economics bProduce reports of recoverable tons for incremental cash 

discounted cash cost/rate of return, cost curves, and re

Developed by USGS, publicly available

Based 

data wi

up

Figure 5. The USGS coal assessment project is designed to provide regional estimates of econorecoverable resources (reserves). Data collection and geological modeling are typically the most phase. Once the geology model is complete, the GIS program allocates the available coal resouvarious mine models. Finally, a program developed in-house called CoalVal performs the econo
Environme

Societal, 

Technic

Restriction

Mining in 

Gillette Coa

Wyomin

Figure 6. In addition to subtracting previously mined out resources, coal restricted by societal anenvironmental constraints are subtracted to determine the remaining available resources. An ec

analysis of the available resources yields an estimate of reserves for the study area.
The GIS Process of Merging Layers or T

The GIS Process of Merging Layers or T

of Data into More Meaningful Interpret

of Data into More Meaningful Interpret

Figure 7. The availability of GIS coverages for land, restrictions, geology, etc. greatly facilitate process.
GIS stu

to min

Coal toby couresoureach m

Available Resource Areas Input into Co

Result

AcreaIn SitIn Sit

Figure 8. The first step in an economic evaluation is importing the coal volumes into CoalVal from mine models. This example is from an evaluation of the Pittsburgh coal bed in Pennsylvania, but data imported are the same CoalVal is scheduled for publication in 2006
CoalVal - Mine Model Equipme

Figure 9. CoalVal provides a series of tables to add and cost out mine equipment.
CoalVal Mine Model Assumption

Oth

Mine 

MinRe

Out-

Figure 10. Mine models assumptions including productivity, dilution, and recovery rates are also data is based on published regional statistics and actual equipment pricing costs, as well as input verification of assumptions by coal mines in the region.
Mine Model Employees

Figure 11. Input for the manpower table is also regionally-based from published labor statistics acompany information. CoalVal will be published with all the basic tables completed as place marit will be the user’s responsibility to supply current information.
CoalVal - Discounted Cash Flow Sum

Figure 12. The final result of the economic evaluation is a report summing the number of tons at price (including a discounted rate of return) for each area and mine model for the entire project ar
Coal Resource/Reserve Cost Curve Coal Resource/Reserve Cost Curve

Billions of tons

Current Sales Price ($/ton)

1.0 4.0 2.0 7.

3.0 5.0 6.0

40.0045.0035.0030.0025.00

3.0 Billion T.

4.5 Billion T.

@ $35.00/ton

@ $31.25/ton

Cost Curve

$26.18

Resources

Reserves

Figure 13. Once the cost of all the available tons are determined, a resource cost curve can be dea current sales price of $31.25/ton, about 3 billion tons would be economic. Any coal tons with a tprice of $31.25 or less would be considered reserves. Thus, the block shown in fig. 12 at $26.18 freserves category. If the price were to increase to $35.00/ton, and additional 1.5 billion tons would the reserves category. It must be stressed, that the determination of reserves is an ongoing procebe revalidated as market and mining costs, and other economic and technological factors change.
PRB B

and G

Coal 

Figure 14. This is the location of the Gillette Coal Field, Wyoming where the initial PRB coal asseproject is starting. The Powder River Basin (PRB) represents the single most productive coal bas

producing nearly 40% of the nation’s coal. Just the Wyoming portion of the basin produced 403 m

2005 (U.S. Bureau of Land Management, 2006). Furthermore, the announced additional coal devsignificant. Peabody’s new School Creek mine (60 miles south of Gillette) alone is expected to co

late 2008 producing 30 million to 40 million short tons/yr (Platts Coal Outlook, 2006).
Current PRB Assessment Status

3⁄4 Current Database:3⁄4 Two Geologists for approximately one year3⁄4 About 4,000 points from WY Geological Survey3⁄4 Plan to complete Gillette coalfield assessment by 

Dec., 2006

3⁄4 Assessment of the north and northwest portions 

the PRB will begin following completion of the Gillcoal field evaluation.

Original 

– 2,200 points

New oil & gas wells – 2,330 points 

New CBM wells – 7,470 points 

TOTAL – 12,000 points

Figure 15. The current USGS PRB assessment status. When completed, the resulting database 

provide one of the most extensive drill hole compilations for the PRB available to the public. The next section represent preliminary assessment work and may be modified for the final report.
Current Assessment Status

Current Assessment Status

Original Database (2002) Current 

Channel Area

Figure 16. Comparison of the original Gillette coal field assessment coal assessment drill hole dataothers, 2002) to the current assessment database. The extensive drilling activity associated with co(CBM) development has resulted in a relatively dense drilling pattern which, by itself, helps define tsignificant channel area where the coal beds are thin or absent.
Preliminary Preliminary Assessment Resu

Assessment Resu

• Minor changes in coal bed correlation

Minor changes in coal bed correlation

• Major down Major down-dip channel will be a dip channel will be a 

restriction to surface mining restriction to surface mining

Figure 17. The preliminary interpretation of the massive amount of new data has resulted in sevefindings. Both are related to the channel geometry defined by the substantial amount of new drilliinformation.
Previous Coal Bed Correlation

Previous Coal Bed Correlation

(USGS Miscellaneous Investigations Series, Map I

USGS 

Anderson Coal Bed (Upper Wyodak, 1990)

Canyon Bed (Lower Wyodak, 1990)

~10 Miles

Figure 18. A portion of a published NW-SE cross section through the channel area based on widewell logs (Pierce, F. W., and others, 1990). 
Correlation Changes with Infill Drilli

Correlation Changes with Infill Drill

(USGS Miscellaneous Investigations Series, Map I-19

USGS 

School Bed

S

mith Bed

Anderson Bed

Canyon Bed

Felix Bed

PRELIMINARY

Channel Area

Figure 19. Closer-spaced drilling reveals minor revisions in the coal bed correlations. Dotted line

previous correlations. The Anderson/Canyon coal beds, which are the major beds in the current of the Gillette coal field split, thin, and (or) are absent in and immediately adjacent to the channel Smith coal bed thickens rapidly west of the major channel area Both the Smith and the Andersonare all part of the Anderson-Wyodak coal zone after Flores and others (1999).
Correlation Changes with Infill Drillin

Correlation Changes with Infill Drillin

S

c

h

o

S

m

Canyon Bed

And

F

elix

PRELIM

Channel Area

Figure 20. Expanded view of infill drilling (fig.19) showing greater detail for the geophysical logs.
East-West Cross West Cross 

Sections Through Sections Through 

Channel area Channel area

PRELIMINARY

N

W 

Xsect 1

Xsect 3

Xsect 2

Anderson Bed present

Smith

Channel(s), 

“no coal zone”

Figure 21. East-west cross sections through the channel confirm the scenario shown in figs. 19 a

the Smith thickens and the Anderson/Canyon (Wyodak) beds are thin or absent westward. Drill h

Anderson bed present are displayed with a solid green dot to create a simple areal distribution mahighs in the Smith coal can indicate the presence of an underlying Wyodak “no-coal zone” (Ashle
Comparison of Anderson Bed - 2002 Study and Current Asse

Wright

0 ft.40 ft.80 ft.120 ft.160 ft.200 ft.

Major channel in Upper 

Wyodak Coal Seam

Correlations

Incomplete

ChannelEdge

A

Preliminary Isopach Anderson Bed

CURRENT ASSESSMENT

PRELIMINARY

Minor Channel

Anderson Bed present

Coal

Thickness

Figure 22. Comparison of a preliminary isopach map from the current assessment and that from Ellis obvious that the total coal resources in the final assessment results will be impacted by improved delin

areas. The end results should provide a more realistic appraisal of the available coal resources. 
Overbu

Overb

Isop

Isop

Gillette C

Gillette C

(Upper W

(Upper W

(2002 

Anderson - W

Figure 23. Overburden isopach for the Anderson/Wyodak bed (Ellis and others, 2002). Fortunatthe major channel lies in areas of deeper cover in the western portion of the coal field.
Stripping R

Stripping R

Gillette Co

Gillette Co

(Upper Wy

(Upper Wy

Wright

Gillette

500 ft. Overburden1000 ft. Overburden

(2002 Stu

Anderson - Wyo

Current Assessm

include models dow

Stripping Ra

Figure 24. Stripping ratio map for the Anderson/Wyodak bed (Ellis and others, 2002). We plan to coevaluation of the Gillette coal field down to a 10:1 stripping ratio during the current coal assessment.
3⁄4 Gillette coal field3⁄4 Birney-Custer-Recluse 

coal fields (BCR)

3⁄4 Sheridan-Birney 

coal fields

Powder River Powder RiverBasinStudy Areas Study Areas

Figure 25. Once the Gillette coal field portion of the PRB is completed, the assessment will move to 

northwest into the Birney-Custer-Recluse (BCR) and Sheridan-Birney coal fields.
North-South Cross South Cross-Section Section 

BCR Study Area BCR Study Area

BCR Area 

Figure 26. The coal beds including the Anderson and Canyon beds tend to thin northward from the Gille

however, more coal beds are generally present. 
Anderson Isopach Anderson Isopach Canyon Isopach Canyon Isopach Pawnee Isopach Pawnee Isopach Kno

Kno

• Maximum thickness = 86’ • Maximum thickness = 98’

• Good extent• Significant areas with thick

coal

• Maximum thickness = 48’• Good extent

• Maxim• Good •Trunc

Major Coal Bed Distributions in the 

Figure 27. Although the coal beds are generally not as thick and widespread as those in the Gillette c

significant coal resources are present in the BCR coal field.
PRB Coal Resource Assessment Sum

PRB Coal Resource Assessment Sum

3⁄4 Extensive CBM and additional oil and gas developm

Extensive CBM and additional oil and gas developm

especially in the Gillette coal field, has provided an especially in the Gillette coal field, has provided an unprecedented amount of down unprecedented amount of down

-hole geological dat

hole geological dat

3⁄4 Better definition of channel/no Better definition of channel/no

-coal areas that form 

coal areas that form 

to mining will be possible. to mining will be possible.

3⁄4 These additional data will provide a more robust eva

These additional data will provide a more robust ev

of the single most productive U.S. coal basin. of the single most productive U.S. coal basin.

3⁄4 The Gillette coal field assessment, including the min

The Gillette coal field assessment, including the min

economic evaluation, is planned for completion by t

economic evaluation, is planned for completion by t

of 2006. of 2006.

3⁄4 The geologic portion of the coal The geologic portion of the coal assessment work w

assessment work w

to the northern and northwestern portions of the PR

to the northern and northwestern portions of the PR

before the end of 2006 while the Gillette engineerin

before the end of 2006 while the Gillette engineerin

studies are finalized. studies are finalized.

Figure 28. PRB Assessment Summary.
References References

Ashley, M., 2006, Wyodak Coal, Tongue River Member of the Fort Union Formation, Powder River 

nion Formation, Powder Rive

Wyoming: "No-Coal Zones" and Their Effects on Coalbed Methane Production; Sea Coal Zones" and Their Effects on Coalbed Methane Production; Search and D

rch and D

#10094, #10094, http://www.searchanddiscovery.com/documents/2005/ashley/index.ht http://www.searchanddiscovery.com/documents/2005/ashley/index.htm

Ellis, M. S., Molnia, C. L.. Osmonson, L. M., Ochs, A. M., Rohrbacher, T. J., Mercier, T., and Robe

2002, Evaluation of Economically Extractable Coal Resources in the Gillette Coal Field, PowdWyoming; U.S. Geological Survey Open-File Report 02-180, 48 p.

Flores, R.M., Ochs, A.M., Bader, L.R., Johnson, R.C., and Vogle, D., 1999, Framework geology of 

coal in the Powder River Basin; Chapter PF, in U.S. Geological Survey Professional Paper 162

Pierce, F. W., Johnson, E.A., Molnia, C.L., and Sigleo, W.R., 1990, Cross-sections showing coal st

southeastern Powder River Basin, Wyoming: U.S. Geological Survey, Miscellaneous InvestigaMap I-1959-B.

Platts Coal Outlook, 2006; v. 30, No. 11, Platts Coal Outlook, 2006; v. 30, No. 11, http://www.platts.com

Rohrbacher, T. J., Luppens, J. A., Osmonson, L. M., Scott, D. C. Rohrbacher, T. J., Luppens, J. A., Osmonson, L. M., Scott, D. C., and Freeman, P. A., 2005, An ex

, and Freeman, P. A., 2005, An ex

review of the U.S. Geological Survey energy resource program’s economically recoverable co

s economically recoverable co

assessment methodology assessment methodology—report and comments: U.S. Geological Survey Open-File Report 2

U.S. Bureau of Land Management, 2006, U.S. Bureau of Land Management, 2006,Powder River Basin Coal Production; http://www.wy.blm.gov/mineral http://www.wy.blm.gov/minerals/coal/prb/PRB_coalpro.htm

Figure 29. References