Tar sands

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Image:Oil sands open pit mining.jpg 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. On average bitumen contains 83.2% carbon, 10.4% hydrogen, 0.94% oxygen, 0.36% nitrogen and 4.8% sulphur.

Contents

Location

Tar sands deposits are found all over the world, with the largest deposits located in Venezuela and Alberta, Canada. While only recently judged a proven reserve of oil (that is, economically extractible at current technology levels), 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.

Extraction process

Image:Extraction separation cell.jpg 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] Provided that the water chemistry is appropriate to allow 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. 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 for upgrading into synthetic crude oil.

It is estimated that around 80% of the Alberta tar sands are too far below the surface for the current open-pit mining technique. Techniques are being developed to extract the oil below the surface. These techniques requires a massive injection of steam into a deposit, thus liberating the bitumen underground, and channelling it to extraction points where it would be liquified before reaching the surface.[2] This type of extraction requires a traditional oil well working in tandem with a steam injection machine. 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 oil sands deposit has an estimated reserve production capacity of 750,000 barrels (150,000 m³) of crude oil per day using the current hot water processes. As traditional or conventional sources of oil suffer from depletion, new sources of oil such as oil sands will increasingly be relied upon to make up the difference in future global oil production. This synthetic crude oil process takes two tons of tar sand to fill one barrel of upgraded synthetic crude oil.

In 2005, University of Toronto researcher Charles Jia developed a means to convert the fluid coke byproduct of oil sand extraction to activated carbon, potentially reducing waste in the extraction process.[3]

Environmental Impact

Tar sands development has a direct impact on local and planetary ecosystems. In Alberta, this form of oil extraction completely destroys the boreal forest, the bogs, the rivers as well as the natural landscape. The mining industry believes that the boreal forest will eventually colonize the reclaimed lands, yet 30 years after the opening of the first open pit mine near Fort McMurray, Alberta, no land is considered by the Alberta Government as having been "restored."

Furthermore, for every barrel of synthetic oil produced in Alberta, more than 80 kg of greenhouse gases are released into the atmosphere and between 3 and 5 barrels of waste water are dumped into tailing ponds. The forecasted growth in synthetic oil production in Alberta also threatens Canada's international commitments. In ratifying the Kyoto Protocol, Canada agreed to reduce, by 2012, its greenhouse gas emissions by 6 percent with respect to the reference year (1990). In 2002, Canada's total greenhouse gas emissions had increased by 24 percent since 1990.

See also

External links

da:Tjæresand de:Ölsand fr:Sable bitumineux

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