Page - October 25, 2007
The tar sands are made up mostly of sand. Only 10-12 per cent is bitumen – a very heavy crude oil that must be heavily processed and refined to be turned into synthetic crude oil.
People who live near tar sands projects in Northern Alberta have been noticing the water levels in lakes and rivers decreasing as oil production has accelerated.
Extracting oil from the tar sands involves three major processes
that deplete water and emit greenhouse gases: surface mining (also
known as strip mining), in-situ extraction (or "deep mining"), and
the upgrading process. Immense amounts of water are used for tar
sands operations - currently 349 million cubic metres per year,
twice the amount of water used by the city of Calgary - and 90 per
cent of this cannot be returned to the river afterwards. People
who live near tar sands projects in northern Alberta have been
noticing the water levels in lakes and rivers decreasing as oil
production has accelerated.
Surface Mining
Tar sands located within 100 metres from the Rarth's surface are
considered "mineable," and so the first layer of rock and soil,
known as overburden, is dug up with earthmovers so the underlying
tar sands can be accessed. (Before this can happen, trees will
have been clearcut and wetlands drained and demolished.) Then the
tar sands are removed, and processed by "washing" with very hot
water to separate the oil from the sand and clay it is mixed in
with. For every two tonnes of tar sands that are removed from the
ground, one barrel of synthetic crude oil is produced.
Transporting and processing this amount of material means that each
barrel of oil derived from the tar sands uses 250 cubic feet of
natural gas, and between two and five barrels of water.
Hydrotransport is becoming more and more common for mined tar sands
as well: once extracted from the mine, the tar sands are mixed with
hot water and caustic soda to produce a liquefied product that can
be pumped through a pipeline to a processing facility where the oil
will be separated from the tar.
In Situ Mining
Most tar sands lie much deeper than 100 metres from the surface,
and can only be extracted by more complex processes. The main
process in use in Alberta's tar sands is known as SAGD -
steam-assisted gravity drainage. SAGD injects high pressure steam
underground to separate the oil from the sand and make it liquid
enough to flow on its own. It is then pumped to the surface to be
processed further and refined. Using this method of extraction uses
two and half to four barrels of water per barrel of oil, and 1000
cubic feet of natural gas.
Upgrading
The oil that is extracted from the tar sands, bitumen, is one of
the lowest quality oils available in the world. In order to be
turned into synthetic crude oil, it must be heavily processed and
refined. This also involves a great deal of water, which produces
steam for hydrocoking and hydrocracking - intense processes that
break the bitumen into smaller lighter molecules, and remove
impurities such as nitrogen and sulphur.
Other Water Use
The fact that tar sands operations are mega-projects means that
water is used in large quantities for reasons not specific to the
tar sands - cleaning, putting out fires, toilets and drinking water
for thousands of workers. Industrial operations also require water
for operating pumps, producing steam for turbines, and cooling in
evaporative cooling systems.