Oil sands: a response to the depletion of oil reserves?

Oil sands - or bituminous sands - are a mix of water, sand and bitumen, which is a highly viscous, almost solid form of crude oil. As conventional oil becomes increasingly scarce, extraction is a major challenge. However, oil sands extraction is a complex operation, which often causes environmental problems. This is a major R&D challenge for oil companies.

New countries with black gold resources

Most deposits of oil sands are located in Canada, in Athabasca in the north of the province of Alberta. The stakes are huge: there are over 300 billion1 barrels of this resource out of 1700 billion barrels of oil on-site! Canada has now become the main oil supplier to the United States, in front of Saudi Arabia.

 

Oil sands have oil reserves equivalent to those of Saudi Arabia.

However, this abundant resource is very difficult to extract - so difficult in fact that oil companies took little interest until conventional oil reserves started to run out.

Oil sands extraction uses as much energy as it provides.

False. Producing a barrel of light oil from oil sands uses 20-25% of its final energy. In other words, one barrel is used to produce 4-5 barrels, meaning that there is a positive gain, even if extracting this type of deposit requires much more energy than conventional deposits (1 barrel for every 15).

Unconventional extraction techniques...

Oil sands are located at depths of between a few dozen meters to several hundred meters.

Those nearest the surface are extracted via open pit mining:

   • First, the ground is cleared and the topsoil set aside to be used later to rehabilitate the site after extraction operations are finished.

   • A quarry is hollowed out to access the deposits and extract the sands.

Specially-designed trucks weighing over 365 tons and as high as 3-story buildings carry out this colossal work.

For deeper deposits, thermal methods are currently used to liquefy the bitumen inside the deposit. Steam is injected underground via horizontal wells, raising the temperature of the bitumen and making it less viscous and easier to pump out. This type of extraction has a lower on-site footprint than the mining technique because only a small area above ground is affected. One of two different processes are generally used:

   • The Cyclic Steam Stimulation process (CSS) involves using the same well to alternately inject steam and extract bitumen. The steam liquefies the bitumen and makes pumping possible.

   • The Steam Assisted Gravity Drainage (SAGD) process is based on twin horizontal wells. Steam is injected through the upper well to liquefy the bitumen and then the water-bitumen mix recovered is pumped out through the lower well.

The choice of process depends on the features of each individual deposit.

... but more environmentally responsible

Producing and processing oil sands has significant environmental impact:

   • It requires large volumes of water.

   • It requires a lot of energy (steam, electricity and heat) and therefore generates carbon emissions.

Oil sands extraction produces large quantities of sulfur, which is toxic for the environment.

True and False. Sulfur is one of the main by-products of oil sands
(it is estimated that by 2015, the annual volume of sulfur recovered could be as high as 5 million tons). However, this sulfur is not necessarily harmful to the environment. It is stored on-site in inert form or exported, often to make fertilizer, avoiding recourse to a technique with high carbon emissions (pyrite combustion).

Since 1996, 40 of China's 600 fertilizer plants have been converted to use Canadian sulfur. This has reduced the amount of CO₂ discharged into the atmosphere by 250,000 tons every year².

Companies are currently focusing their research and development to reduce the environmental impact. The following solutions are currently being studied:

   • Optimizing water recycling and increasing use of brackish water for on-site extraction to reduce the use of freshwater sources.

   • Developing other production processes that use less water, such as adding a solvent to the steam injected, or injecting only solvent, producing bitumen that is still mixed with sand, and over the longer term, on-site combustion, electrical heating, etc.

   • Capturing and storing the CO₂ emitted during extraction.

There is still an impact on the ecosystem, even after extraction operations have finished.

True and False. The rehabilitation of end-of-life extraction sites is a major issue and is strictly regulated. Environmental protection is taken into account from the design stage, for example, corridors are built for local wildlife, reforesting plans are drawn up, etc. So, once the site has been restored, it is returned to close to its original condition.

With energy demand on the increase, oil sands represent an opportunity to renew oil resources. Studies are underway to make the extraction of these sands sustainable, economically viable and environmentally-friendly.