Orinoco belt

the area enclosed in blue is the Orinoco belt. the area enclosed in red is the east Venezualan basin

Venezuala's Orinoco belt is the name given to one of the largest deposits of petroleum on Planet Earth.

The petroleum lies under one of the world's regions of rich biodiversity. Much of it is remote, making it hard to extract the petroleum. The petroleum found in the Orinoco is relatively high in Sulphur. Much of the Petroleum is deposited in tar sands, which adds to the difficulty in extracting it.

The second or third largest deposits of petroleum, that under Saudi Arabia, produces "light crude oil" -- it is considered the most economically desirable. It is relatively low in Sulphur, which is good because the Sulphur component in burned oil is highly polluting. And Saudi oil contains a higher proportion of the lighter hydrocarbon fractions, which makes it easier to refine, and more energy dense.

Canada also has large tar sands deposits in Alberta, and has a longer history of extraction. In Alberta tar sands that lie on the surface, or near the surface is strip mined. Separating the petroleum from the sand is both energy intensive, and requires a large amount of fresh water. Alberta requires the energy equivalent of a barrel of oil, for each barrel of oil produced. And it requires a barrel of fresh water, during the refining process.