Page 98 - Oil and Gas Production Handbook An Introduction to Oil and Gas Production

chemistry is appropriate (the water is
adjusted with chemical additives), it allows
bitumen to separate from sand and clay.
The combination of hot water and
agitation releases bitumen from the oil
sand, and allows small air bubbles to
attach to the bitumen droplets. The
bitumen froth floats to the top of
separation vessels, and is further treated
to remove residual water and fine solids. It
can then be transported and processed
the same way as extra heavy crude.

It is estimated that around 80% of tar sands are too far below the surface for
current open-cast mining techniques. Techniques are being developed to
extract the oil below the surface. This requires a massive injection of steam
into a deposit, thus liberating the bitumen underground, and channeling it to
extraction points where it would be liquefied before reaching the surface.
The tar sands of Canada (Alberta) and Venezuela are estimated at 250
billion barrels, equivalent to the total reserves of Saudi Arabia.

7.1.3 Oil shale
Most oil shales are fine-grained sedimentary rocks containing relatively large
amounts of organic matter from which significant amounts of shale oil and
combustible gas can be extracted by destructive distillation. One of the
2
largest known locations is the oil shale locked in the 40,000 km (16,000 sq.
miles) Green River Formation in Colorado, Utah, and Wyoming.

Oil shale differs from coal in that organic matter in shales has a higher
atomic hydrogen to carbon ratio. Coal also has an organic to inorganic
matter ratio of more than 4, i.e. 75 to 5, while oil shales have a higher
content of sedimentary rock. Sources estimate the world reserves of oil
shales at more than 2.5 trillion barrels.

Oil shales are thought to form when algae and sediment deposit in lakes,
lagoons and swamps where an anaerobic (oxygen-free) environment
prevent the breakdown of organic matter, thus allowing it to accumulate in
thick layers. That is later covered with overlying rock to be baked under high
temperature and pressure. However the heat and pressure was lower than in
oil and gas reservoirs.
The shale can be strip-mined and processed with distillation. Extraction with
fracturing and heating is still relatively unproven. Companies are

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