In Alberta, 80 percent, or roughly 135 billion barrels, of the oil sands are buried deep below the surface and are not accessible by open pit mining. To access these valuable resources, industries use an in-situ extraction method called Steam-Assisted Gravity Drainage (SAGD). Because in-situ extraction takes place mainly under the Earth’s surface, less land is disturbed during the extraction process than surface mining.
In 2012, Alberta’s total in-situ bitumen production was about 990,000 barrels per day, a 16 percent increase over 2011. This accounts for 52 percent of Alberta’s total crude bitumen production. By 2022 in-situ production is expected to reach 2.2 million barrels per day.
SAGD is a thermal in-situ production process where parallel wells are drilled horizontally into an underground bitumen reservoir. Steam is produced at the surface and injected into the reservoir through the shallower of the two wells (the injection well). The steam heats the bitumen to a point where gravity allows it to flow down to the lower well (the producer well) where the mixture of bitumen and water is then pumped to the surface. The water and bitumen are separated at the surface.
Approximately two to four barrels of water are required per barrel of oil produced; however, approximately 90 percent of the water used can be recycled back through the process, so only half a barrel of new water (make-up water) is added to the process for each barrel of oil produced. In comparison, oil sands mining operations use approximately 2–4 barrels of make-up water and conventional oil operations use approximately 0.1-0.3 barrels of make-up water per barrel of oil produced.
Treatment of the recycled water consumes energy and generates waste. Greenhouse gas emissions for SAGD projects are around 0.06 tonnes of carbon dioxide equivalent per barrel of bitumen produced. As water becomes a more critical resource, operators have had to start looking for and using alternative technologies to increase water recycle rates while minimizing the amount of energy consumed in the water treatment process.
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