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How is oil extracted from tar sands?

How is oil extracted from tar sands?
Tar sands mining in Fort McMurray, Alberta. (Source: iStock, Credit: Dan Barnes Photography)

Oil sands (or tar sands as they are sometimes inaccurately referred to) represent a vast resource of recoverable oil1. Vast quantities of oil sands are located around the world, particularly in Canada, eastern Venezuela and Saudia Arabia1. About 314 billion barrels of recoverable oil exists within Alberta alone1. Other deposits are also found in Utah, parts of Russia, Congo, and Madagascar to mention a few1

What are tar sands?

Tar sands (more accurately referred to as oil sands) are defined as a low quality form of oil composed of a mixture of bitumen, sand, clay and water1. Generally, bitumen is a thick, molasses-like substance2. For this reason, this oil resource is sometimes referred to as “tar sands,” but that term is inaccurate as bitumen and tar (asphalt) are completely different3. In fact, bitumen consists of hydrocarbons similar to molecules found in liquid oil and used to produce gasoline and other petroleum products2. More specifically, the technical term for the oil extracted from oil sands is crude bitumen4. To explain this simply, this is a very thick, heavy oil that doesn’t flow in its natural state4

The methods of oil extraction:

To begin with, there are two ways to extract crude bitumen and turn it into a usable product: open-pit mining and in situ (in place)5. However, the technique used largely depends on the depth of the deposit5. Therefore, on the one hand, oil sands will be surface mined and sent to a bitumen processing plant if the deposit is close to the surface. On the other hand, oil sands will be extracted in situ, if the deposit is deep below the surface5.

Open mining bitumen extraction

To conduct open-pit mining, the oil sand deposit must be less than 100 metres deep7. Firstly, companies create the open-pit by first clearing the land of trees and other vegetation and stripping the top layer of the soil6. Also, after draining water and diverting river channels where necessary, operators create mine faces to begin the extraction process6. Then, oil companies extract the bitumen from the oil sands via a process that mixes the oil sands with hot water to effectively wash the bitumen away from the sand7.

Finally, the mining companies must reclaim the mining site after the bitumen resources have been extracted8. This means they must return the land to a more natural state either by replanting trees or reintroducing wildlife8.

In situ bitumen extraction:

Moreover, in situ extraction, also known as steam assisted gravity drainage (SAGD)7, used to access deeper deposits, involves the drilling of two horizontal wells: steam pipe and well pipe6. Firstly, high-pressured and heated steam is injected into the oil sand deposit through the upper steam pipe. This steam heats up the bitumen and separates it from the sand7. Then, by heating the bitumen, it becomes fluid enough to easily flow to the lower well pipe and be pumped out of the ground7.

How is oil extracted from tar sands?
How is oil extracted from tar sands? (Source: Energy Information Administration, Government of Alberta/Alberta Energy, Credit: Alyson Hurt, Ayodha Ouditt and Andrew Prince / NPR) Available at: https://www.npr.org/2012/08/16/158907708/infographic-how-tar-sands-oil-is-produced
How is oil extracted from tar sands?
The two methods of extraction. (Source: Phil Ebersole) Available at: https://philebersole.wordpress.com/tag/tar-sands/

What happens next?

After extraction, the upgrading process takes its turn. Specifically, this upgrading process transforms the bitumen from the thick, molasses-like oil, into a lighter and higher quality synthetic crude oil via the addition of hydrogen7. Then, the resulting oil is sent to a refinery where it is changed into gasoline, diesel, jet fuel and other petroleum products ready for use7

Energy source

Both methods of extraction are energy-intensive processes5. Consequently, large amounts of energy are needed to generate heat to extract the bitumen from oil sands and upgrade it to synthetic crude oil5. In general, this energy source typically comes from natural gas5. In order to extract a single barrel of bitumen and upgrade it, one needs about 280–350 kilo watts per hour of energy from burning natural gas9. Because natural gas is relatively clean burning, readily available, and currently cheap to use it is most commonly used7.

Environmental costs

As with the extraction, production and use of any fossil fuel, negative environmental impacts come hand-in-hand with extracting oil from oil sands10. In general, the oil sands industry contributes to climate change, water contamination, air pollution and the destruction of wildlife and ecosystems10. Greenhouse gas emissions from oil sands are increasing for both mining and in situ production, despite progress made in reducing emission intensity from bitumen production11. Oil sands mining and in situ production pose a number of risks affecting the quantity and quality of water resources in the region, from both groundwater and surface water bodies (rivers and lakes)7. In summary, the oil sands industry extracting bitumen and producing millions of gallons of synthetic crude oil each year are clearly threatening our planet.

https://www.youtube.com/watch?v=AuSJSRL4sjA&feature=emb_logo
Oil Sands is a form of heavy oil found in sand and rock primarily in Northern Alberta, Canada. (Source: Student Energy) Available at: https://www.youtube.com/watch?v=AuSJSRL4sjA&feature=emb_logo

References:

  1. Oil Change International. (2019). Tar Sands – Oil Change International. [online] Available at: http://priceofoil.org/campaigns/extreme-fossil-fuels/no-extreme-fossil-fuels-tar-sands/#:~:text=Tar%20sands%20(also%20known%20as,with%20sand%2C%20clay%20and%20water.&text=It%20is%20either%20strip%20mined,to%20flow%20to%20the%20surface.
  2. Union of Concerned Scientists. (2020). What Are Tar Sands? [online] Available at: https://www.ucsusa.org/resources/what-are-tar-sands.
  3. “What Are the Oil Sands | Canada’s Oil Sands Facts & Information.” (2020). CAPP. July 31, 2020. https://www.capp.ca/oil/what-are-the-oil-sands/.
  4. Alberta Energy and Utilities Board. (2005). Alberta’s Reserves 2004 and Supply/Demand Outlook/Overview (2005), Statistical Series (ST) 2005-98, p.2-1.
  5. Oil Sands Magazine, Oil Sands 101: Process Overview (2016). Oil Sands Magazine. [online] Available at: https://www.oilsandsmagazine.com/technical/oilsands-101
  6. Andrew Prince, NPR (2012). Infographic; How Tar Sands Oil Is Produced. [online] Available at: https://www.npr.org/2012/08/16/158907708/infographic-how-tar-sands-oil-is-produced?t=1594826336381
  7. Woynillowicz, D., Severson-Baker, C. and Raynolds, M. (2005). SANDS Fever Oil THE ENVIRONMENTAL IMPLICATIONS OF CANADA’S OIL SANDS RUSH. [online] Available at: http://large.stanford.edu/courses/2014/ph240/montgomery1/docs/OilSands72.pdf.
  8. Natural Resources Canada (2010). Oil Sands: Land Use and Reclamation | Natural Resources Canada. [online] Nrcan.gc.ca. Available at: https://www.nrcan.gc.ca/energy/publications/18740.
  9. Appendix VI – Fact Sheets” (2006). Alberta Oil Sands Consultations Multistakeholder Committee Interim Report. Government of Alberta. 30 November p. 14. 
  10. Energyeducation.ca. (2018). Environmental impacts of oil sands – Energy Education. [online] Available at: https://energyeducation.ca/encyclopedia/Environmental_impacts_of_oil_sands.
  11. “OIL SANDS ENVIRONMENTAL IMPACTS.” (2014) https://ceri.ca/assets/files/Study_143_Full_Report.pdf.

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