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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)

Surprisingly, oil extracted from tar sands represents a large supply of potentially recoverable oil. In fact, Alberta, Canada, eastern Venezuela and Saudia Arabia contain vast quantities of tar sands1. Specifically, 314 billion barrels of oil are lying below Alberta alone1.

What are tar sands?

Tar sands (also known 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. In fact, it 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 tar sands is crude bitumen3. To explain this simply, this is a very thick, heavy oil that doesn’t flow in its natural state3

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)4. However, the technique used largely depends on the depth of the deposit4. Therefore, on the one hand, tar sands will be surface mined and sent to a bitumen processing plant if the deposit is close to the surface. On the other hand, tar sands will be extracted in situ, if the deposit is deep below the surface4.

Open mining bitumen extraction

To undergo open-pit mining, the tar sand deposit must be less than 100 metres deep6. Firstly, companies create the open-pit by first clearing the land of trees and other vegetation and stripping the top layer of the soil5. Also, after draining water and diverting river channels where necessary, operators create mine faces to begin the extraction process5. 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 sand6.

Finally, the mining companies must reclaim the mining site after the bitumen resources have been extracted7. This means they must return the land to a more natural state either by replanting trees or reintroducing wildlife7.

In situ bitumen extraction:

Moreover, in situ extraction, also known as steam assisted gravity drainage (SAGD)6, used to access deeper deposits, involves the drilling of two horizontal wells: steam pipe and well pipe5. Firstly, high-pressured and heated steam is injected into the tar sand deposit through the upper steam pipe. This steam will heat up the bitumen and separate it from the sand6. Then, by heating the bitumen, it becomes fluid enough to easily flow to the lower well pipe and be pumped out of the ground6.

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 will transform the bitumen from the thick, molasses-like oil, into a lighter and higher quality synthetic crude oil via the addition of hydrogen6. Then, the resulting oil is sent to a refinery where it will be changed into gasoline, diesel, jet fuel and other petroleum products ready for use6

Energy source

Additionally, both methods of extraction are energy-intensive processes4. Consequently, large amounts of energy are needed to generate heat to extract the bitumen from the oil sands and upgrade it to synthetic crude oil4. In general, this energy source typically comes from natural gas4. Significantly, 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 gas6. Because natural gas is relatively clean burning, readily available, and currently cheap to use it is most commonly used4.

Environmental costs

In summary, as with the extraction, production and use of any fossil fuel, negative environmental impacts come hand-in-hand with extracting oil from tar sands9. Tar sands have a devastating effect on climate change, water consumption and contamination, and wildlife9. Also, the methods of extraction, which are energy- and water-intensive, contribute to air and water pollution and destroying the environment5. From poisoning rivers and water tables, to killing wildlife, destroying ecosystems and increasing greenhouse gas emissions6, the oil industries extracting bitumen and producing millions of gallons of synthetic crude oil each year are clearly threatening our planet.

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. Alberta Energy and Utilities Board. (2005). Alberta’s Reserves 2004 and Supply/Demand Outlook/Overview (2005), Statistical Series (ST) 2005-98, p.2-1.
  4. Oil Sands Magazine, Oil Sands 101: Process Overview (2016). Oil Sands Magazine. [online] Available at: https://www.oilsandsmagazine.com/technical/oilsands-101
  5. 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
  6. 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.
  7. 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.
  8. Appendix VI – Fact Sheets” (PDF). Alberta Oil Sands Consultations Multistakeholder Committee Interim Report. Government of Alberta. 30 November 2006. p. 14. 
  9. Energyeducation.ca. (2018). Environmental impacts of oil sands – Energy Education. [online] Available at: https://energyeducation.ca/encyclopedia/Environmental_impacts_of_oil_sands.

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