Extraction

 How is bitumen recovered from oil sands?

Bitumen within the McMurray Formation can be economically strip mined down to depths of about 75 meters. When an area is to be mined, roads are plowed, forests are clearcut, muskeg is stripped away, and layers of overburden are removed. Shovels take 90-ton bites of bitumen-laced sandstone from the mine face, and load trucks that can haul almost a million pounds of ore.

Eighty percent of Alberta’s oil sands lie too deep to be recovered by strip mining. Instead, steam is injected into an ore body that lies 150 meters or more beneath the surface. Heated bitumen, sometimes made less viscous with the addition of chemicals like propane or carbon dioxide, is able to flow out of sandstones of the McMurray Formation down to a horizontal collecting well. Unlike strip mining, steam assisted gravity drainage does not require a great deal of bitumen/sand separation, so tailings ponds are not required. On the other hand, this in situ method does require tremendous energy inputs–usually natural gas–to generate steam. Water is obtained from deep, often brackish, aquifers rather than from surface sources.

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