Coal Resources & Reserves
Coal Production & Mining
Coal Maps & Projects
Powder River Basin
Coal Resources & Reserves
The question is often posed, “How much coal does Wyoming have?” This question does not have a simple answer.
While there remains a large amount of coal in the earth, scientists must answer the question by determining
whether or not the coal can be mined or if it is too deep. The volume of coal in-place underground is called
a coal resource. It represents a large amount of coal underground based on drill hole depth and thickness. Only
coal less than 6,000 feet is considered economic. Coal is usually mined safely less than 3,500 feet deep:
any deeper and the weight of the overlying rock could collapse. Coalbed methane resources are found at a depth more
than 250 feet, but can go as deep as 6,000 feet. As a result this is considered the maximum depth for extraction.
Miners only count that part of the coal resource that is economically mineable,
called the coal reserve. The coal reserve only counts that volume of drill hole
information that has coal less than 3,500 feet deep, has a mineable continuity
to the seam, a coal deposit thickness appropriate enough to fit coal mining
equipment, and does not have surface disturbances to civilization such as towns,
major roads, power plants or abandoned mines. There are geologic reasons not to
count some coal resources as coal reserves also, such as the coal near faults or
steeply dipping strata or coal that is too thin to mine. These parameters must
be subtracted to come up with the coal reserve.
There is an important geological question about coal reserves: When assigning
coal resources to a reserve classification it is assumed that the coal can be
mined in an economic way. Coal reserves represent a small percentage of the
economic coal resources that can be mined today. This is a changeable
percentage, as the price of coal and the technology used to mine that coal
changes over time.
Coal resources and reserves can be subdivided into a series of categories based
on geologic certainty. With exploration, when a hole is drilled and coal is
encountered, this coal intercept is logged in terms of its depth and thickness.
When another hole is drilled in the same vicinity a measurement can be taken of
the coal intercepts, which can determine the likelihood of whether that coal is
the same mineable coal or not. Then it can be inferred from the data that there
may be a correlation of the coals, which when combined, can determine the volume
of coal in that area and whether it can be mined based on thickness and depth.
Measured coal is the amount of coal based on a close proximity to the drill hole,
which is one-quarter mile, as defined by the U.S. Geological Survey, and former
Bureau of Mines. This direct measurement usually includes information for coal
rank and quality as well. Indicated coal is the amount of coal based on
direct measurement and reasonable geologic assumptions, such as individual coal
bed correlations. Indicated coal is that coal beyond measured coal at
one-quarter to a distance of three quarters of a mile from the drill hole. Often
coal reserves are defined by the term “demonstrated reserves,” or the amount of
measured and indicated (combined) coal near a drill hole or outcrop. Inferred
coal refers to that coal which is beyond the three quarter mile designation of
known coal that is estimated to still contain a coal intercept. This is not
widely used, especially in the western United States, where Cretaceous and
Tertiary coals are not usually that contiguous for miles at a time. Inferred
coal represents that coal from three quarters of a mile to three miles in
diameter away from the drill hole. Together, the Demonstrated and Inferred
categories represent coal tonnages that have been identified with drill hole or
outcrop measurements (USGS, 1983). Since drill hole information does not exist
for coal everywhere, then the amount of undiscovered coal in the U.S. is much
greater than the identified coal.
Demonstrated Reserve Base
To count how much coal is in-place for each state, the Energy Information Administration
(EIA) counts the ‘Demonstrated Reserve Base,”or DRB. This was based on the number of drill
holes and measured sections of coal by state back in the 1970s. Currently, Wyoming ranks
third on the list (after Montana and Illinois) at 61 billion tons. This database has not
been updated for new coal exploration since 1993. The latest study on coal reserves in
Wyoming was conducted by the U.S. Geological Survey’s for the Powder River Basin (PRB).
As of 2015, USGS Professional Paper 1809, at USGS Newsroom,
states that the PRB of Wyoming and Montana contain an estimated in-place coal resource
of 1.16 trillion short tons of coal. Of that total, the recoverable coal is
162 billion tons (BT). This is similar to measured and indicated coal, or the Demonstrated
Reserve Base of coal. The economically recoverable coal resources portion of this amount,
at today’s coal prices, is 24.6 BT.
For the Wyoming part of the Powder River Basin (PRB) this is 855 billion tons for
original in-place coal resource. The coal availability of Wyoming’s PRB is 768
billion tons. The recoverable coal for Wyoming’s part of the PRB is about 127
Wyoming has the greatest resource of coal in the nation. If this is extrapolated
to the entire state, then a new conservative estimate for the Wyoming DRB would
be approximately 165.1 billion tons.
Economic Recoverable Reserve Today
USGS WY-MT PRB (2015)
Wyoming PRB only
Estimated Wyoming Entire State (From N. Jones, 2010, Keystone Industry Coal
The table above shows the most recent studies on coal resources and reserves in Wyoming and Montana. Note that the recoverable and economically recoverable coal
resources for the entire state of Wyoming are only estimated and not calculated. Original coal resources for all of Wyoming may count some coal deeper than 6,000 feet.
All values in billion short tons. Data sources from USGS (2008-2013) and WSGS (2010). Approximately two billion tons of coal have been mined in Wyoming since 2010, and should be subtracted from these calculations.
Chris Carroll (307) 766-2286 Ext. 243