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how is it extracted?
Tar sands can be extracted and processed using a variety of techniques which can be classified as ‘surface mining’, where the tar sands are dug out and transported for crushing and processing, or in-situ (underground) techniques, where the oil is made to flow by injecting steam, solvents and/or hot air into the sands. In shallower deposits, surface strip mining with huge shovels and trucks can be used. The resulting mixture of bitumen, sand and water is then taken to a crusher. Once broken up the bitumen is separated from water and other materials.
tar sands TAR SANDS OR OIL SANDS CONSIST OF A THICK, DENSE TYPE OF OIL CALLED BITUMEN MIXED WITH SAND, WATER AND CLAY. EXTRACTION REQUIRES ENORMOUS AMOUNTS OF ENERGY AND WATER, RELEASES VAST AMOUNTS OF GREENHOUSE GASES AND OTHER POLLUTANTS AND IS DEVASTATING HUGE TRACTS OF BOREAL FOREST AND WETLANDS IN CANADA.
Deeper deposits, below around 225ft (69m), are extracted using various in-situ techniques. The most commonly used, Steam Assisted Gravity Drainage (SAGD) and Cyclic Steam Stimulation (CSS) involve injecting the deposit with steam, which heats the bitumen to make it flow. The bitumen is then pumped out and transported for further processing. Of the two methods, SAGD is cheaper and has been widely adopted by the tar sands industry. Other in-situ processes have been experimented with, such as using solvents instead of steam, and Toe to Heel Air Injection (THAI), where the bitumen is ignited underground. Once the bitumen has been extracted and separated from the sand and water it is then either diluted with light oil or natural gas liquids to make ‘dilbit’ (diluted bitumen) which can be piped to refineries, or ‘upgraded’, where it is partially refined to produce ‘syncrude’ (synthetic crude). All forms of tar sands extraction require huge amounts of energy and water, and are highly carbon intensive. However, in-situ processes, which will be increasingly required to access most of the tar sands deposits, use even more resources than surface mining, and have resulted in oil spills as heated, pressurised bitumen escapes into the environment (see ‘Oil Spills’ section below).
what is it?
Tar sands, also known as oil sands or bituminous sands, are a mixture of sand, water and clay with a dense, sticky, semi-solid form of crude oil called bitumen. Although very similar in appearance, technically bitumen is not the same as tar, which is a man made product. Bitumen needs to be heated or diluted to make it flow, which distinguishes it from 'extra-heavy crude', another form of high density unconventional oil, the largest deposits of which occur in Venezuela's Orinoco Belt (see 'Extra heavy oil' in 'Other Unconventional Fossil Fuels' factsheet). Most of the world's tar sands are found in Canada where extraction is taking place on an enormous scale, with devastating effects on the local environment and critical implications for climate change. Most of the Canadian tar sands are in three major deposits in Northern Alberta which together cover more than 140,000 km2, an area larger than England. In 2011, Alberta's bitumen production reached over 1.7 million barrels (270,278 m3) per day.1 Tar sands also occur in other parts of the world, with the next largest deposits in Kazakhstan and Russia. Exploration and test projects have been carried out in Russia, Madagascar, Congo (Brazzaville), and Utah in the USA.