How is oil extracted from tar sands?

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.

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.

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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.