The Tar Sands Industry
Currently, oil is not produced from tar sands on a significant commercial level in the United States; in fact, only Canada has a large-scale commercial tar sands industry, though a small amount of oil from tar sands is produced commercially in Venezuela. The Canadian tar sands industry is centered in Alberta, and more than one million barrels of synthetic oil are produced from these resources per day. Currently, tar sands represent about 40% of Canada’s oil production, and output is expanding rapidly. Approximately 20% of U.S. crude oil and products come from Canada, and a substantial portion of this amount comes from tar sands. The tar sands are extracted both by mining and in situ recovery methods (see below). Canadian tar sands are different than U.S. tar sands in that Canadian tar sands are water wetted, while U.S tar sands are hydrocarbon wetted. As a result of this difference, extraction techniques for the tar sands in Utah will be different than for those in Alberta.
Recently, prices for crude oil have again risen to levels that may make tar-sands-based oil production in the United States commercially attractive, and both government and industry are interested in pursuing the development of tar sands oil resources as an alternative to conventional oil .
Tar Sands Extraction and Processing
Tar Sands Open Pit Mining, Alberta, Canada
Tar sands deposits near the surface can be recovered by open pit mining techniques. New methods introduced in the 1990s considerably improved the efficiency of tar sands mining, thus reducing the cost. These systems use large hydraulic and electrically powered shovels to dig up tar sands and load them into enormous trucks that can carry up to 320 tons of tar sands per load.
Tar Sands Extraction Separation Cell, Alberta, Canada
After mining, the tar sands are transported to an extraction plant. where a hot water process separates the bitumen from sand, water, and minerals. The separation takes place in separation cells. Hot water is added to the sand, and the resulting slurry is piped to the extraction plant where it is agitated. The combination of hot water and agitation releases bitumen from the oil sand, and causes tiny air bubbles to attach to the bitumen droplets, that float to the top of the separation vessel, where the bitumen can be skimmed off. Further processing removes residual water and solids. The bitumen is then transported and eventually upgraded into synthetic crude oil.
See the Photos page for additional photos of tar sand processing facilities.
About two tons of tar sands are required to produce one barrel of oil. Roughly 75% of the bitumen can be recovered from sand. After oil extraction, the spent sand and other materials are then returned to the mine, which is eventually reclaimed.
In-situ production methods are used on bitumen deposits buried too deep for mining to be economically recovered. These techniques include steam injection. solvent injection, and firefloods, in which oxygen is injected and part of the resource burned to provide heat. So far steam injection has been the favoured method. Some of these extraction methods require large amounts of both water and energy (for heating and pumping).
Both mining and processing of tar sands involve a variety of environmental impacts. such as global warming and greenhouse gas emissions, disturbance of mined land; impacts on wildlife and air and water quality. The development of a commercial tar sands industry in the U.S. would also have significant social and economic impacts on local communities. Of special concern in the relatively arid western United States is the large amount of water required for tar sands processing; currently, tar sands extraction and processing require several barrels of water for each barrel of oil produced, though some of the water can be recycled.
For More Information
Additional information on tar sands is available through the Web. Visit the Links page to access sites with more information.