Abstract - Coal recoverability in the Hilight quadrangle

U.S. DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL SURVEY

Coal recoverability in the Hilight quadrangle, Powder River Basin, Wyoming:
a prototype study in a western coal field

by
Lee M. Osmonson, Timothy J. Rohrbacher, Carol L. Molnia,
and Gerald L. Sullivan

Open-File Report 00-103

Electronic edition

February 2000

Abstract

Accurate data regarding the amount of coal within the United States is essential for making informed decisions concerning national, regional, and local energy policies. As a prototype study by the U.S. Geological Survey (USGS), our investigation of coal resources within the Hilight 7½-minute quadrangle, an area in the southern Powder River Basin, Wyoming, has resulted in estimates of the amount of available coal, recoverable coal, and economically recoverable coal. We calculated the original coal resources of the area to be 3.6 billion short tons. Our estimates show that (1) available coal, which is that part of the original coal resource that is accessible for mine development under current regulatory and land-use constraints, represents about 95 percent of the original resource; (2) recoverable coal, which is the amount of coal that remains after mining losses and cleaning losses are subtracted from the available coal, represents about 89 percent of the original resource; and (3) economically recoverable coal, which is that part of the recoverable coal that can be mined, cleaned, and marketed at a profit, represents only 10.7 percent of the original resource, at a coal sales price of as much as $3.00 per ton. At a coal sales price of as much as $4.00 per ton, 20.3 percent of the original resource is economically recoverable. The average sales price for coal in the southern Powder River Basin was $3.22 per ton (as of January 1998).

Acknowledgments
This report is the culmination of efforts of several people. Charlie Gaskill of the U.S. Bureau of Land Management supplied land-use information. Within the USGS, Vickie L. Clark provided valuable computer assistance and M. Devereux Carter furnished resource data from the National Coal Resources Data System (NCRDS). Laura R. H. Biewick provided the data files from which recoverable resources were calculated. Laura N. R. Roberts, Edwin R. Landis, and W.R. Keefer provided thoughtful reviews of the manuscript.

Introduction
Procedures and methodologies used to estimate the Nation’s reserves of coal have traditionally used historical mining recovery factors and applied them throughout coal regions to obtain the estimated recoverable coal tonnage. These traditional estimates did not consider restrictions related to the environment and societal concerns, site-specific geology, mining and preparation technology, and economics. However, as this study shows, these restrictions significantly impact the amount of coal that is ultimately economically recoverable.

Our study includes resource analysis (table 1) and economic evaluation (table 2) of

Table 1. Original coal resources, unavailable resources, available resources, mining losses, and recoverable resources in the Hilight quadrangle by coal ownership. (All tonnage values are in short tons; not rounded to significant figures)

Wyodak Coal Unit	Coal Ownership	*Original Resources*	Previously Mined Resources	*Unavailable Resources²* (fig. 4)	Percent of Original Resource	*Available Resources*	Percent of Original Resource	*Mining Losses on Available Coal*	Percent of Original Resource	*Recoverable Resources*	Percent of Original Resource

Main	Federal	2,733,082,513	0	127,589,484	4.7	2,605,493,029	95.3	182,384,512	6.7	2,423,108,517	88.7
	State	111,366,604	0	1,011,607	0.9	110,354,997	99.1	7,724,850	6.9	102,630,147	92.2
	Private	1,090,774	0	0	0.0	1,090,774	100.0	76,354	7.0	1,014,420	93.0
	TOTAL	2,845,539,891	0	128,601,091	4.5	2,716,938,800	95.5	190,185,716	6.7	2,526,753,084	88.8

Lower	Federal	758,941,142	0	37,618,615	5.0	721,322,527	95.0	50,492,577	6.7	670,829,950	88.4
	State	31,578,843	0	385,941	1.2	31,192,902	98.8	2,183,503	6.9	29,009,399	91.9
	Private	211,031	0	0	0.0	211,031	100.0	14,772	7.0	196,259	93.0
	TOTAL	790,731,016	0	38,004,556	4.8	752,726,460	95.2	52,690,852	6.7	700,035,608	88.5

TOTAL	Federal	3,492,023,655	0	165,208,099	4.7	3,326,815,556	95.3	232,877,089	6.7	3,093,938,467	88.6
	State	142,945,447	0	1,397,548	1.0	141,547,899	99.0	9,908,353	6.9	131,639,546	92.1
	Private	1,301,805	0	0	0.0	1,301,805	100.0	91,126	7.0	1,210,679	93.0
	GRAND TOTAL	3,636,270,907	0	166,605,647	4.6	3,469,665,260	95.4	242,876,568	6.7	3,226,788,692	88.7

²Mining restricted by the Hilight gas plant, a railroad corridor, producing oil and gas wells, and an alluvial valley floor.

Table 2. Economically recoverable coal resources by sales-price level in the Hilight quadrangle. (All tonnage values are in short tons; not rounded to significant figures)

Coal Ownership	Original Resources	Recoverable Resources	Economically Recoverable Resources: *As much as $3.00 Per Ton Sales Price*	Percent of Original Resource	Economically Recoverable Resources: *As much as $4.00 Per Ton Sales Price*	Percent of Original Resource	Economically Recoverable Resources: *As much as $5.00 Per Ton Sales Price*	Percent of Original Resource
Federal	3,492,023,655	3,093,938,467	371,887,218	10.6	692,589,682	19.8	1,347,968,414	38.6
State	142,945,447	131,639,546	16,637,301	11.6	43,574,200	30.5	67,055,981	46.9
Private	1,301,805	1,210,679	668,421	51.3	1,014,420	77.9	1,014,420	77.9
GRAND TOTAL	3,636,270,907	3,226,788,692	389,192,940	10.7	737,178,302	20.3	1,416,038,815	38.9

coal in the Hilight 7½-minute quadrangle, located about 35 miles south of Gillette, Wyoming, within the Powder River Basin of northeastern Wyoming (fig. 1). The Powder River Basin contains some of the most significant deposits of low-sulfur subbituminous coal in the world (Molnia and Pierce, 1992) including thick Wyodak coals studied in this report. These coals are in the Fort Union Formation (Paleocene).

The area contained within the Hilight quadrangle was studied previously by the U.S. Geological Survey (Molnia and others, 1997) to determine the amount of coal available for mining (available coal). Coal recoverability studies are a natural continuation of coal availability studies; this report describes the results of our coal recoverability calculations and compares them with the availability calculation previously completed by Molnia and others (1997). The results of similar coal recoverability evaluations of other quadrangles within the Appalachian and Illinois Basins are found in Rohrbacher and others (1993a, 1993b, 1994a, 1994b); Scott (1995, 1997); Teeters (1997); and U.S. Bureau of Mines (1995).

DEFINITIONS

This study includes determinations of available, recoverable, and economically recoverable resources. Figure 2 shows how estimates of available coal are derived (Carter and Gardner, 1989; Eggleston and others, 1990; Molnia and others, 1999). Figure 3 shows how estimates of recoverable coal resources and economically recoverable coal resources are derived.

The following definitions apply:

Available resource—That part of the original coal resource that is accessible for mine development under current regulatory and land-use constraints. Alluvial valley floors and producing oil and gas wells are examples of constraints which may restrict coal mining in their immediate vicinities.

Recoverable resource—That part of the available coal that is left after mining losses and cleaning losses are subtracted. Costs involved with the extraction and cleaning of the coal are not considered, nor is the potential selling price of the coal.

Economically recoverable resource—That part of the recoverable coal that can be mined, cleaned, and marketed at a profit (depends on the mine location, the characteristics of the coal bed, the quality of the coal, and the mining methods used). Also known as a reserve.

The recoverable resource is a subset of the available resource; the economically recoverable resource is a subset of the recoverable resource. For example, some available coal resources may not be extractable and thus would not be considered recoverable resources. Similarly, some recoverable coal resources may not be profitable to extract and thus would not be considered economically recoverable resources.

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U.S. Geological Survey Open-File Report 00-103

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