The term oil shale
generally refers to any sedimentary rock that contains solid bituminous
materials (called kerogen) that are released as petroleum-like liquids
when the rock is heated in the chemical process of pyrolysis. Oil shale
was formed millions of years ago by deposition of silt and organic
debris on lake beds and sea bottoms. Over long periods of time, heat and
pressure transformed the materials into oil shale in a process similar
to the process that forms oil; however, the heat and pressure were not
as great. Oil shale generally contains enough oil that it will burn
without any additional processing, and it is known as "the rock
that burns".
Oil shale can be mined
and processed to generate oil similar to oil pumped from conventional
oil wells; however, extracting oil from oil shale is more complex than
conventional oil recovery and currently is more expensive. The oil
substances in oil shale are solid and cannot be pumped directly out of
the ground. The oil shale must first be mined and then heated to a high
temperature (a process called retorting); the resultant liquid must then
be separated and collected. An alternative but currently experimental
process referred to as in situ retorting involves heating the oil shale
while it is still underground, and then pumping the resulting liquid to
the surface.
Oil Shale
Resources
Location
of the Green River Formation Oil Shale and Its Main Basins
While oil shale is found
in many places worldwide, by far the largest deposits in the world are
found in the United States in the Green River Formation, which covers
portions of Colorado, Utah, and Wyoming. Estimates of the oil resource
in place within the Green River Formation range from 1.2 to 1.8 trillion
barrels. Not all resources in place are recoverable; however, even a
moderate estimate of 800 billion barrels of recoverable oil from oil
shale in the Green River Formation is three times greater than the
proven oil reserves of Saudi Arabia. Present U.S. demand for petroleum
products is about 20 million barrels per day. If oil shale could be used
to meet a quarter of that demand, the estimated 800 billion barrels of
recoverable oil from the Green River Formation would last for more than
400 years1.
More than 70% of the
total oil shale acreage in the Green River Formation, including the
richest and thickest oil shale deposits, is under federally owned and
managed lands. Thus, the federal government directly controls access to
the most commercially attractive portions of the oil shale resource
base.
The Oil Shale Industry
While oil shale has been used as fuel and as a source of oil in small
quantities for many years, few countries currently produce oil from oil
shale on a significant commercial level. Many countries do not have
significant oil shale resources, but in those countries that do have
significant oil shale resources, the oil shale industry has not
developed because historically, the cost of oil derived from oil shale
has been significantly higher than conventional pumped oil. The lack of
commercial viability of oil shale-derived oil has in turn inhibited the
development of better technologies that might reduce its cost.
Relatively high prices
for conventional oil in the 1970s and 1980s stimulated interest and some
development of better oil shale technology, but oil prices eventually
fell, and major research and development activities largely ceased. More
recently, prices for crude oil have again risen to levels that may make
oil shale-based oil production commercially viable, and both governments
and industry are interested in pursuing the development of oil shale as
an alternative to conventional oil.
Oil Shale Mining and
Processing
Oil shale can be mined using one of two methods: underground mining
using the room-and-pillar method or surface mining. After mining, the
oil shale is transported to a facility for retorting, a heating process
that separates the oil fractions of oil shale from the mineral
fraction.. The vessel in which retorting takes place is known as a
retort. After retorting, the oil must be upgraded by further processing
before it can be sent to a refinery, and the spent shale must be
disposed of. Spent shale may be disposed of in surface impoundments, or
as fill in graded areas; it may also be dispoed of in previously mined
areas. Eventually, the mined land is reclaimed. Both mining and
processing of oil shale involve a variety of environmental impacts, such
as global warming and greenhouse gas emissions, disturbance of mined
land, disposal of spent shale, use of water resources, and impacts on
air and water quality. The development of a commercial oil shale
industry in the United States would also have significant social and
economic impacts on local communities. Other impediments to development
of the oil shale industry in the United States include the relatively
high cost of producing oil from oil shale (currently greater than $60
per barrel), and the lack of regulations to lease oil shale.
Surface Retorting
While current technologies are adequate for oil shale mining, the
technology for surface retorting has not been successfully applied at a
commercially viable level in the United States, although technical
viability has been demonstrated. Further development and testing of
surface retorting technology is needed before the method is likely to
succeed on a commercial scale.
In Situ Retorting
Shell Oil is currently developing an in situ conversion process (ICP). The
process involves heating underground oil shale, using electric heaters
placed in deep vertical holes drilled through a section of oil shale. The
volume of oil shale is heated over a period of two to three years, until
it reaches 650–700 °F, at which point oil is released from the shale.
The released product is gathered in collection wells positioned within the
heated zone.
Shell's
current plan involves use of ground-freezing technology to establish an
underground barrier called a "freeze wall" around the perimeter
of the extraction zone. The freeze wall is created by pumping refrigerated
fluid through a series of wells drilled around the extraction zone. The
freeze wall prevents groundwater from entering the extraction zone, and
keeps hydrocarbons and other products generated by the in-situ retorting
from leaving the project perimeter.
Shell's
process is currently unproven at a commercial scale, but is regarded by
the U.S. Department of Energy as a very promising technology. Confirmation
of the technical feasibility of the concept, however, hinges on the
resolution of two major technical issues: controlling groundwater during
production and preventing subsurface environmental problems, including
groundwater impacts.1
Both mining
and processing of oil shale involve a variety of environmental impacts,
such as global warming and greenhouse gas emissions, disturbance of mined
land; impacts on wildlife and air and water quality. The development of a
commercial oil shale industry in the U.S. would also have significant
social and economic impacts on local communities. Of special concern in
the relatively arid western United States is the large amount of water
required for oil shale processing; currently, oil shale extraction and
processing require several barrels of water for each barrel of oil
produced, though some of the water can be recycled.
Credit: The U.S.
Department of the Interior, Bureau of Land Management Argonne National
Laboratory The Oil Shale and
Tar Sands Programmatic Environmental Impact Statement
Data
compiled from The British Antarctic Study, NASA, Environment Canada,
UNEP, EPA and other sources as stated and credited Researched by Charles
Welch-Updated daily This Website is a project of the The Ozone Hole Inc.
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