Geology Reference
In-Depth Information
This consists of “tight” (dense) formations of sedimentary rock that are not perme-
able enough to allow the pumping of the oil trapped inside. This oil is in the form
of kerogen, a solid mixture of organic compounds. Extracting oil from kerogen is
difficult and expensive, and to date oil shale deposits have not been widely deve-
loped. But there is an estimated 2.8 to 3.3 trillion barrels of oil in oil shale deposits
worldwide, 62 percent of which are in the United States. Aside from hydrofracking,
technology for extracting such oil includes igniting the shale underground, which
allows light oil to migrate out of the kerogen to pumping stations.
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Also known as “oil sands,” these are deposits of heavy oil so viscous they do not
flow. Tar sands are extracted by injecting hot steam into deposits, which heats the
sands and makes the tar more liquid so that it can be pumped out. The process re-
quires large amounts of water and energy, is environmentally destructive, and only
makes economic sense when oil prices are high. The world's largest tar sands de-
posits are in the Athabasca region of Alberta, Canada. If approved, the controversi-
al Keystone XL Pipeline would transport oil from the Athabascan fields across the
United States to terminals on the Gulf Coast.
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This is a natural gas extracted from coal beds. It is usually produced by drilling
a borehole into a coal seam, reducing the pressure of water flowing through the
seam, and allowing the gas held in the seam to flow up the borehole to the surface.
This is a process used to produce “syngas” (synthesis gas), a fuel mixture of hydro-
gen, carbon monoxide, and carbon dioxide. Originally used in the eighteenth cen-
tury to create heat and light, modern gasification plants supply fuel for a wide range
of uses. One advantage of gasification is that carbon dioxide (the leading green-
