USGS Powder River Basin Coal Assessment Features an Estimate of the Reserve Base

The latest coal resource assessment of the Powder River Basin showcases the newly revised USGS’ assessment methodology, which, for the first time, includes an estimate of the reserve base for the entire basin.

The coal reserve base includes those resources that are currently economic (reserves), but also may encompass those parts of a resource that have a reasonable potential for becoming economically available within planning horizons. The complete, final assessment results are available in two USGS publications released today: Professional Paper 1809 and Data Series 912.

The Powder River Basin contains one of the largest resources of low-sulfur, low-ash, subbituminous coal in the world and is the single most important coal basin in the United States.

The most important distinction between this Powder River Basin coal assessment and other, prior assessments, was the inclusion of mining and economic analyses to develop an estimate of the portion of the total resource that is potentially recoverable, not just the original (in-place) resources.  Prior resource assessments relied on net coal thickness maps for only selected beds, which provided only in-place resource estimates.

The key to performing the economic analyses was gathering and interpreting a sufficient amount of recent geological data from the extensive coal bed methane development over the past 20 years in the Powder River Basin. This wealth of new data was essential to enable modeling and mapping of all of the significant individual coal beds over the entire Powder River Basin for the first time.

The revised USGS assessment methodology resulted in an estimated original resource of about 1.16 trillion short tons in the Powder River Basin, of which 162 billion short tons are considered recoverable resources (coal reserve base) at a stripping ratio of 10:1 or less.  An estimated 25 billion short tons of that coal reserve base met the definition of reserves.   A 10:1 stripping ratio is approximately estimated by dividing the total thickness of rock mined to the total thickness of coal recovered.

The coal reserve base includes those resources that are currently economic (reserves), but also may encompass those parts of a resource that have a reasonable potential for becoming economically available. This reserve estimate does not mean that the total amount of coal left in the Powder River Basin could be produced by surface mining technologies. The costs of mining and coal sales prices are not static as both tend to increase over time if supported by demand. If future market prices continue to exceed mining costs, portions of the coal reserve base would be elevated to reserve status (and the converse).

The estimate of the current reserves along with the total coal reserve base provide more meaningful resource information for use by energy planners from local to national perspectives rather than just total in-place resource quantities..

Although no underground mining in the Powder River Basin is expected to occur in the foreseeable future, a substantial, deeper coal resource in beds 10–20 feet thick is estimated at 304 billion short tons in the region.

The USGS Energy Resources Program research efforts yield comprehensive, digital assessments of the quantity, quality, location, and accessibility of the Nation’s coal resources.

To learn more about this or other geologic assessments, please visit the USGS Energy Resources Program website. Stay up to date with USGS energy science by subscribing to our newsletter or by following us on Twitter.