Canada's oilsands are a mixture of bitumen, sand, water, and clay. Each grain of sand is enveloped by a thin film of water that also contains extremely fine particles of clay and other trace materials. In turn, the bitumen, a naturally occurring viscous mixture of heavier hydrocarbons, surrounds the sand and water. Other components vary locally with the deposits, but may include sulfur (about 5 wt %), minerals, heavy metals, and other nonhydrocarbon materials, some of which have commercial potential. In its raw state, bitumen is a black, asphalt-like oil, as thick as cold molasses and heavier than water.
Often composed of molecules containing as many as 2,000 carbon atoms, bitumen is a complex hydrocarbon molecule with a relatively high ratio of carbon to hydrogen and other chemical attributes, making it uneconomic or impossible to process for most refineries. As a result, it must be processed by high-conversion facilities designed specifically for bitumen or heavy oils or be upgraded and customized to a light crude oil equivalent.
Water makes up about 4 wt % of the oilsands. Without the water envelope, the oil and sand could not be separated by the hot water extraction process now being used.
The Athabasca oilsands are one example of a petroleum resource that has lost its lighter components. The bitumen was formed largely by the effects of bacterial processes, water flows, and oxidation in the reservoir.
Oilsands occur with various levels of bitumen saturation. The bitumen in the oilsands mined at Syncrude Canada Ltd.'s Mildred Lake lease, for example, averages 10.5 wt % and is made up of 50-60% oil, 30-35% resins, and 15-25% asphaltenes. Sands with more than 10% bitumen are considered rich. Those with less than 7% are currently considered to be of no economic interest.
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