Tar sands

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Tar sands, also referred to as oil sands or bituminous sands, are a combination of clay, sand, water, and bitumen. Technically speaking, the bitumen is neither oil nor tar, but a semisolid, degraded form of oil which will not flow toward producing wells under normal conditions, making it difficult and expensive to produce. Tar sands are mined to extract the oil-like bitumen which is upgraded into synthetic crude oil or refined directly into petroleum products by specialized refineries. Conventional oil is extracted by drilling traditional wells into the ground whereas tar sand deposits are mined using strip mining techniques, or persuaded to flow into producing wells by in situ techniques which reduce the bitumen's viscosity with steam and/or solvents. On average bitumen contains 83.2% carbon, 10.4% hydrogen, 0.94% oxygen, 0.36% nitrogen and 4.8% sulphur.

1 Location
2 Extraction process
3 Environmental Impacts
4 External links

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Location

Tar sands deposits are found in over 70 countries throughout the world, but three quarters of the world's reserves are in two regions, Venezuela and Alberta, Canada. While tar sands were used by the ancient Mesopotamians and Canadian Indians, they have only recently become considered to be a major part of the world's oil reserves, that is, they have become economically extractible at current prices with current technology. To distinguish the bitumen and synthetic oil extracted from tar sands from the free-flowing hydrocarbon mixtures known as crude oil that oil companies have traditionally produced from oil wells, tar sands are often referred to as non-conventional oil. Tar sands represent as much as 66% of the world's total reserves of oil, with at least 1.7 trillion (1.7×10¹²) barrels in the Canadian Athabasca Tar Sands and 1.6 trillion (1.6×10¹²) barrels in the Venezuelan Orinoco tar sands, compared to 1.75 trillion (1.75×10¹²) barrels of conventional oil worldwide, most of it in Saudi Arabia and other Middle-Eastern countries.

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Extraction process

Image:Extraction separation cell.jpg Hot water and caustic soda (NaOH) 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 tar 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 to use the open-pit mining technique used by the large producers. Techniques are being developed (and used to a degree) to extract this deeper oil. These techniques involve 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 large source of water, 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.

There has also been research into other methods of extraction of heavy tar sand. One of these is a method where hot air is pumped into the reserve, causing a combustion of parts of the oil reserve. The heat and pressure caused by the combustion then forces the reserves away from the combustion zone, and into a drilled well. In the province of Alberta, a pilot project using the technology is currently being undertaken by the Canadian oil company Petrobank.

The Canadian Athabasca tar 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 tar 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 tar sand extraction to activated carbon, potentially reducing waste in the extraction process.[3]

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Environmental Impacts

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 forecast 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% with respect to the reference year (1990). In 2002, Canada's total greenhouse gas emissions had increased by 24% since 1990.

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