This introduction to the oil sands explores where oil sands are found, the size of Alberta’s reserves, the processes required to extract the oil and the types of oil recovered — synthetic crude oil (SCO) or dilbit.
What Are Oil Sands?
Everyone knows that Alberta has large deposits of oil sands. But what exactly does that mean? This introduction to the oil sands explores the geography, production methods, and environmental impacts of the oil sands.
When clay, sand, minerals, water and bitumen exist together, they are referred to as oil sands. Bitumen, a heavy, viscous form of hydrocarbon, is the end product.
The oil sand mixture is relatively loose and will typically contain 10 per cent bitumen, 5 per cent water and 85 per cent solids in the form of sand, fine solids or clay. Depending on the depth of the deposits, bitumen can either be extracted via in situ production or open pit mining.
It is estimated that there are nearly 2 trillion barrels of oil in the oil sands in Alberta. Almost 10 per cent (or 165 billion barrels) can be recovered using current technologies. This amount represents about 10 per cent of the world’s total proven reserves, and 96 per cent of all oil reserves in Canada.
Where Are the Oil Sands in Alberta?
Oil sands deposits exist in many countries, such as Venezuela and Russia, but there are three distinct deposits in Alberta. The largest is the Athabasca Oil Sands, which covers 93,000 sq. km. Bitumen deposits in the Athabasca Oil Sands can be as thick as 150 m. The Peace River and Cold Lake Oil Sands have an area of 29,000 and 18,000 sq. km, respectively, with deposit depths around 300 to 600 m underground.
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What Does It Take to Get Oil from the Oil Sands?
Parts of the Athabasca Oil Sands are shallow enough for surface mining, at depths up to about 75 m. This area contains 20 per cent of the total bitumen reserves. In surface mining, heavy trucks haul the bitumen-saturated sand to a cleaning facility. Once there, hot water and diluent are applied to separate sand and bitumen.
The unused portion (sand, clay, water, and minerals, commonly referred to as “tailings”) is sent to tailings ponds. The bitumen portion (considered “diluted bitumen” at this point) is sent to upgraders in the province or throughout North America. It takes 2,000 kg of oil sands, mixed with 300 to 635 liters (2 to 4 barrels) of water, to produce a single barrel of synthetic crude oil (SCO).
Deeper deposits use in situ processes for bitumen recovery. In situ processes use steam-assisted gravity drainage (SAGD) or cyclic steam stimulation (CSS) to reduce the viscosity of the bitumen so it can be pumped out of the ground. Using in situ methods, it takes about 80 litres (0.5 barrel) of water to produce one barrel of SCO without any leftover sand.
SAGD uses two wells and two parallel underground lines. Steam is injected into one well while the other well produces water and oil. Want to know what that looks like? Check out the Energy Education post on SAGD for more information and a helpful diagram.
CSS uses a single well to inject steam and produce oil. The reservoir characteristics determine which method will be more effective. GreenLearning has put together a helpful primer on CSS if you want to learn more about it.
What Kind of Oil Is Recovered?
When it comes out of the ground, bitumen is thick and viscous. It requires upgrading or dilution to be useable. Depending on the facility, it will either be processed into synthetic crude oil (SCO) or diluted bitumen (dilbit). SCO can be used in conventional refineries, the same as standard light crude oil. Dilbit must be processed in a high-conversion refinery suitable for heavy oil.
What Are Some Environmental Impacts of the Oil Sands?
Oil sands production generates 70 million tonnes of greenhouse gas emissions per year, roughly 25 per cent of all greenhouse gas emissions in Alberta, or 10 per cent for all of Canada. This figure does not include any of the downstream emissions. It’s just for oil sands production.
In situ production requires significant amounts of steam, generated by burning natural gas. Burning large quantities of natural gas means that in situ production results in higher emissions per barrel of production than oil sands produced by mining.
In a future post, we’ll explore Alberta’s oil and gas emissions in detail. We’ll explain just how much our oil and gas contribute to emissions, both upstream and downstream.
