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Tar sands, also referred to as oil sand or bituminous sand, is a combination of clay, sand, water, and bitumen. Tar sands are mined for the oil rich bitumen which is refined into oil. Conventional oil is extracted by drilling traditional wells into the ground whereas tar sand deposits are mined using strip mining techniques.
Location Tar sands deposits are found all over the world, with the largest deposits located in Venezuela and Alberta, Canada. While not a proven reserve of oil, tar sands represent as much as 66% of the world's deposits of oil, with 34% (286 km³ or 1.8 trillion barrels) in the Venezuelan Orinoco tar sands deposit, 32% (270 km³ or 1.7 trillion barrels) in Canada's Athabasca Tar Sands deposit and the remaining 33% (278 km³ or 1.75 trillion barrels) in conventional oil, much of it in Saudi Arabia and other Middle-Eastern countries.
Refining process  Raw bitumen is separated from the sand in giant separation cells. Hot water is added to the sand, and the resulting slurry is piped to the extraction plant where it is agitated and the oil skimmed from the top. [1] (http://www.oilsandsdiscovery.com/oil_sands_story/extract.html) The combination of hot water, agitation and skimming 'cracks' the bitumen from the clay. Bitumen is much thicker than traditional crude oil, so it must be either mixed with lighter petroleum (either liquid or gas) or chemically split before it can be transported by pipeline.
It is estimated that around 80% of the Alberta tar sands are too far below the surface for the current open-pit mining technique. In situ mining techniques are being established to extract the oil, which requires a massive injection of steam into a deposit, thus 'cracking' the bitumen underground, and channelling it to extraction points where it would be liquified before reaching the surface.[2] (http://www.oilsandsdiscovery.com/oil_sands_story/insitu.html) This type of extraction requires a traditional oil well working in tandem with a steam injection machine. Major disadvantages of this process include the need for a huge local water source, the energy required to boil the water, a large waste water disposal problem, as well as potential environmental damage below the surface. Critics argue that heavy water use makes scaled up production infeasible; proponents argue that water efficiency will improve as the technology is further refined.
The Canadian Athabasca tar sands site has an estimated reserve production capacity of 750,000 barrels (150,000 m³) of crude oil per day using the current hot water process. As traditional or conventional sources of oil suffer from depletion, non conventional sources of oil such as tar sands will increasingly be relied upon to make up the difference in future global oil production.
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