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Recovery or Extraction
Roughly 500 km2 of the 140,000 km2 oil sands deposit in Northern Alberta is currently undergoing surface mining activity.
This is about 3 per cent of total oil sands surface area or 20 per cent of oil sands reserves.
Surface mining uses truck and shovel technology to move sand saturated with bitumen from the mining area to an extraction facility. Surface mining is used to recover oil sands deposits less than 75 meters below the surface, while in-situ technologies are used to recover deeper deposits. The electric and hydraulic shovels used have a capacity of 45 m3 and trucks can carry up to 400 tons of ore.
Trucks move the oil sand to a cleaning facility where it is mixed with hot water and diluent (naphthanic, parafanic) to separate the bitumen from the sand.
Sand, water, fine clays and minerals, or tailings, are separated from the bitumen and diluent and sent to tailings ponds where the sand settles.
The diluted bitumen can be piped to an upgrader on site, if one has been built in conjunction with the mine. Currently in Alberta, four facilities in the Fort McMurray area and one near Fort Saskatchewan, near Edmonton upgrade about 54 per cent of Alberta's crude bitumen production. The remainder is sent to upgraders and refineries throughout North America.
About two tonnes of oil sands must be dug up, moved and processed with 2 to 4 barrels of water to produce one barrel of synthetic crude oil (SCO).
In situ recovery is used for bitumen deposits buried too deeply - more than 75 m - for mining to be practical. Most in situ bitumen and heavy oil production comes from deposits buried more than 350-600 m below the surface.
Steam, solvents or thermal energy make the bitumen flow to the point that it can be pumped by a well to the surface.
Cyclic steam stimulation (CSS) and steam-assisted gravity drainage (SAGD) are effective in situ recovery methods.
- Cyclic Steam Stimulation (CSS) is a thermal production technology in which one well is used to both inject steam and produce oil. Steam is injected at pressures high enough that the hydraulic fractures are induced in the reservoir, allowing steam to access and heat new areas of the reservoir. After weeks or even months, the injection cycle is completed; a few days are allowed for the steam to condense and then the production of oil and water begins. Production initially occurs due to increased reservoir pressures, but later, cycles require artificial lift technologies to produce the remaining oil during the production cycle. This cycle is then repeated after the production rates become too small (as determined by the producer).
CSS is a viable option for deeper reservoirs that have a thick, capping shale to manage the high steam injection pressure. The high injection pressure and multiple recovery mechanisms enable CSS to work effectively with a broader range of reservoirs, especially with heterogeneous characteristics.
- Steam Assisted Gravity Drainage (SAGD) is a thermal production technology which utilizes two parallel horizontal wells, known as a well pair, one to inject steam, and the other to produce water and oil. Initially, steam is circulated in both wells to establish communication between the wells. The top horizontal well then continuously injects steam to heat the reservoir, creating a steam chamber. The oil from the chamber drains to the production well below to allow for production initially through pressure drive, and then by artificial lift or gas lift. The steam injection and oil production happen continuously and simultaneously once production starts. This technology has a high ultimate recovery of oil from the reservoir relative to other in situ production technologies.
No tailings ponds are required for in situ methods of recovery. Sand remains in the ground; only bitumen is removed. An average of 0.5 barrels of water is used to produce one barrel of synthetic crude oil (SCO).
Canada's largest in situ bitumen recovery project is at Cold Lake, Alberta, where deposits are heated by steam injection to bring bitumen to the surface, then diluted with condensate for shipping by pipelines.
New technologies that maximize rates of recovery have been tested, such as pulse technology and vapour recovery extraction (VAPEX). More work is required to make this technology beneficial.
Cold Heavy Oil Production with Sand (CHOPS)
CHOPS allows the deliberate flow of sand into a bitumen well in order to increase the rate of bitumen recovery.
Heavy oil is more viscous than conventional oil but less viscous than bitumen. By introducing sand into the well and producing oil and sand together, the higher viscosity is mitigated by the increased permeability of the deposits - the sand essentially creates wormholes through which the bitumen can flow more easily.
Currently, CHOPS is only employed in the Cold Lake oil sands area.