Re: salvation from tar pits?

Don Winterstein wrote (among other good comments):
 <It's not as clear that this country's vast deposits of oil shale will
ever be exploited, even though prices will almost certainly rise to the
point where such development will become profitable. There'll be
tremendous hue and cry from environmentalists, who--incidentally--so far
don't seem to be getting worked up over the imminent devastation of those
remote parts of Alberta. >

NIMBY! NIMBY! When it comes to oil shales, this won't only be the cry from
environmentalists but also from a large segment of the population in the
Western U.S.

Probably the most economical way to exploit oil shales would be to strip
mine them - if you could ignore the environmental costs like we did for so
many years in the coal industry. The world's largest deposit of oil shale
is in the Green River formation of northwestern Colorado/southwestern
Wyoming. Besides the obvious impact of huge pits and the need to restore
the land, water is probably the biggest concern. This area doesn't get a
lot of rainfall. The water in this region and that flows through this
region is valuable and a source of continual litigation. Most of the Green
River formation is drained by tributaries of the Colorado River. That
means that every stakeholder in the Colorado River system will want a voice
in oil shale development. A sampling of stakeholders would include
Canyonlands National Park (NP), Glen Canyon (Lake Powell) National
Recreation Area (N.R.A.), Grand Canyon NP, Lake Meade N.R.A., Lake Havasu
National Wildlife Refuge (N.W.R.), Cibola N.W.R., Imperial N.W.R., Navajo
Indian Reservation, Havasupai Ind. Res., Hualapai Ind. Res., Fort Mojave
Ind. Res., Chemehuevi Ind. Res., Colorado River Ind. Res., Fort Yuma Ind.
Res., southeast Utah, Nevada (primarily Las Vegas), southern California
(including the city of Los Angeles which imports water via the Colorado
River Aqueduct & the Imperial Valley agriculture via the Coachella Canal),
west-central Arizona (including Phoenix which imports Colorado River water
via the Arizona Canal), U.S. National Forest Service, U.S. Bureau of Land
Management, U.S. Bureau of Reclamation, assorted U.S. military bases, &
Mexico. The environmental costs are so high that large-scale strip mining
of oil shales will probably not be viable in the foreseeable future, at
least here in Colorado.

There are other factors to be considered when extracting oil from oil
shales. Besides the energy costs needed to mine, transport, and crush the
shale, the material has to be heated to around 500 deg. C to decompose the
organic matter into shale oil & gas. I don't have any data at hand that
compare the unit of energy expended per unit of energy recovered for oil
shale.

The amount of energy resources locked up in oil shale is a very tempting
target. According to a report from the Am. Assoc. of Petroleum Geologists
<http://emd.aapg.org/technical_areas/oil_shale.cfm>, "Total world resources
of oil shale are conservatively estimated at 2.6 trillion barrels." Of
this total, the Green River oil shale accounts for an estimated 1.5
trillion barrels. The problem--as many on this list have stated--is how
much is actually recoverable, how fast can it be recovered, and how much
energy and cost must be expended to recover it. There have been several
experimental facilities here in Colorado. None have been profitable.
These experiments included conventional mining and processing facilities as
well as some 'in situ' retort facilities where the shale is heated
underground and oil & gas is then recovered by drilling wells. A major
problem with underground retorting is permeability. Shale is notoriously
impermeable and so you need some method of fracturing the rock to allow the
oil and gas to flow at rates fast enough for recovery. Without extensive
fracturing, the underground facility can only process a very small volume
of oil shale in the immediate vicinity. To exploit the oil shales in this
manner would require a large number of regularly-spaced underground
facilities--each with a well at the surface.

There is another huge resource of energy, natural gas, is locked beneath
the Green River oil shales in the sandstones of the Piceance Basin of
Colorado. (Piceance is usually pronounced as PEE-awnce although I've also
heard it pronounced as 'pissy ants'). Estimates range from 31 to 100 tcf
(trillion cubic feet) of methane gas trapped in tight impermeable
sandstones. This is another example of Glenn's 'billion dollars in bank'
analogy. The Piceance Basin natural gas has never been economic because
its rate of production is usually too slow. One company has been trying to
produce Piceance Basin natural gas. Each well costs ~$1.2 million and they
are drilled on a 40-acre spacing. Because of the low permeability, this
company has sought permission to place wells on a controversial 20-acre
spacing. There have been attempts to fracture these rocks to increase
permeability. The most famous attempts occurred in 1969 and again in 1973
when the U.S. government exploded nuclear bombs 1 mile underground (one at
Rulison and another at Rio Blanco, Colo.) in these impermeable, natural
gas-rich, sandstones. Unfortunately, the only thing produced by these
explosions was a small amount of radioactive gas and a large amount of
political fallout.

Steve
[Disclaimer: Opinion expressed herein are my own and are not to be
attributed to my employer.]
_____________
 Steven M. Smith, Geologist, U.S. Geological Survey
 Box 25046, M.S. 973, DFC, Denver, CO 80225
 Office: (303)236-1192, Fax: (303)236-3200
 Email: smsmith@usgs.gov
 -USGS Nat'l Geochem. Database NURE HSSR Web Site-
  http://pubs.usgs.gov/of/1997/ofr-97-0492/
Received on Thu Jul 1 15:08:08 2004