Recovering the oil
Oil sands are recovered using two main methods: open-pit mining and in situ drilling. The method depends on how deep the reserves are deposited. In Alberta, 97% of the total surface area of the oil sands region could be developed in situ. As of January 2014, there were 100 over active oil sands projects in Alberta. Currently there are only four operational mining projects and one under construction.
Approximately 20% of the oil sands lie close enough to the earth’s surface to be mined, which impacts 3% of the surface area of the oil sands region.
Open-pit mining is similar to many coal-mining operations. Large shovels scoop the oil sands into trucks, which take it to crushers, where the large clumps of clay are broken down. The oil sands is then mixed with water and transported by pipeline to a plant, where the bitumen is separated from the other components. Tailings ponds are an operating facility common to all types of surface mining. In the oil sands, tailings consisting of water, sand, clay and residual oil are pumped to these basins – or ponds – where settling occurs and water is recycled for reuse in the process. When the ponds are no longer required, the land will be reclaimed.
In situ drilling
|The majority of the oil sands lie more than 70 metres (200 feet) below the ground, and are too deep to be mined. These reserves can be recovered in situ (in place) by drilling wells. In situ drilling accounts for 80% of oil sands reserves and these reserves are located below 97% of the land in the oil sands sector. |
Drilling methods disturb a small amount of land and do not require tailings ponds. Advanced technology is used to inject steam, combustion or other sources of heat into the reservoir. The heat warms the bitumen so it can be pumped to the surface through recovery wells.
Advances in technology, such as directional drilling, enable in situ operations to drill multiple wells (sometimes more than 20) from a single location, further reducing surface disturbance.
|The majority of in situ operations use steam-assisted gravity drainage, or SAGD. This method involves pumping steam underground through a horizontal well to liquefy the bitumen, which is then pumped to the surface through a second recovery well. |
A second method – cyclic steam stimulation – pumps steam down a vertical well to soak or liquefy the bitumen, which is then pumped to the surface through the same well. This technique is repeated until the oil is removed.
Watch an animation of the SAGD process