What Are the ‘Geological Challenges’ of WV Coal?
The State Journal
24 September 2012
By Taylor Kuykendall, Reporter
It seems just about every coal company operating in Appalachia has
been talking about "geologic challenges" in their financial
reports. What does that mean?
The State Journal asked experts at Marshall University and West
Virginia University what exactly are some of these challenges to
mining coal in the region. Christopher J. Bise, professor in the
Department of Mining Engineering at West Virginia University, said
some mine roofs are more difficult to stabilize and varying
conditions affect the thickness of a coal seam.
He added that while the coal is found in thinner beds than coal in
some Western basins, it has a higher BTU count, which makes the
coal more valuable.
"As a mining engineer, we use the terms 'minability' of coal
seams: coals seams that can be mined safely and economically,"
said Anthony B. Szwilski, the director of the Center for
Environmental, Geotechnical and Applied Sciences at Marshall
University. "There are many factors that govern the minability of
a coal seam … "
Szwilski said the "easy coal" in West Virginia — coal seams with
thick deposits near the surface —were mined out years ago.
"The minability of coal seams in West Virginia, in general, are
better than any of the coal mining countries I have worked in or
visited: coal seams generally of good thickness, continuous, flat,
of high quality coal, competent coal seam rock strata," he said.
"The coal outcrops (exposed coal seams) at the sides of the
mountains have provided easy access to the coal reserves."
Now, Szwilski said, coal seams mined today and in the future are
getting deeper and getting thinner, increasing the cost per ton to
mine. Techniques such as longwall mining have enabled more
efficient mining of thinner seams, but safety issues at increasing
depths are inherent because of "increasing pressure in the rock
strata around the coal seams," he said.
The increasing pressure can result in methane outbursts and roof
falls into work places.
Ronald Martino, a professor of geology at Marshall University,
said many seams over 1,000 feet deep are considered "too deep to
mine," but some mining difficulties can and have been addressed.
"Underground mining can be impacted by poor roof conditions, coal
seam irregularities and discontinuities like channel washouts,
splits, rapid changes in quality," Martino said. " Engineering
innovation in mining techniques often overcome some of these
Now, there is easier coal to be mined in Wyoming's Powder River
Basin, but its lower BTU rank and higher moisture content makes it
less attractive on a pound-for-pound basis.
"Mined by underground and surface mining methods, Wyoming coals
are geologically younger and softer, and of less quality
sub-bituminous coal of lesser heating value," he said.
Therefore, Szwilski said, the seams are generally very thick and
near the surface. The surface is typically flat, and it is surface
So why is the coal in West Virginia so different than in the
Powder River Basin, aside from the fact it has been mined over a
longer period of time?
"Seams are thickest where there was a balance between the rate of
subsidence of the earth's crust and the rate of peat
accumulation," Martino explained. "The longer these were in
balance, the thicker the seam that will form.
"Seam thickness can be influenced by the ancient landscape:
low-lying areas may have thicker coals whereas hills or uplands
have thin or no coal. Seams also tend to thin toward the edge of
the swamp as it changed to a lake or coastal tidal flats."
Seam thickness and accessibility isn't the only challenge to
mining in the region.
"An interesting feature of mining coal seams in the
Appalachian mountains is mining the coal above or below the water
table, or termed mining above or below drainage," Szwilski said.
"Generally, coal methane gas content increases with depth below
drainage. The water in the coal pores and fractures (cleat) traps
the coal methane, thus the methane gas in the coal seams above the
water table (drainage) has had a greater opportunity to escape
into the surrounding rocks over geological time, resulting (in)
the underground mine (above drainage) being much less gassy."
Those gases can have potential value, but the economics of
increased natural gas supplies has reduced interest in coal bed
"Many West Virginia coal beds have considerable potential for
natural gas production," Martino said. "Prior to the development
of the Marcellus Shale, CBM was a fast-growing industry. This same
potential makes them hazardous to underground mining if not
degassed by drilling ahead of mining or if the mine is not
properly ventilated (as was apparently the case in the Upper Big
Branch mine disaster)."