What are tar sands and how are they mined?

Oil sands are a mixture of sand or clay, water, and bitumen. Bitumen is an extremely thick oil, due to its nature, bitumen must be heavily treated before it can be used in a refinery to create a more traditional petroleum product.

There are many countries with large amounts of oil sands, the United States and Russia have very large deposits. The largest deposits are in Athabasca, Canada with 870 Gbbl of energy and Venezuela with 1200bbl in its Orinoco belt. In total, these countries have deposits roughly equal to the world’s conventional crude oil reserves, although extraction is more difficult and significantly worse on the environment.

With a decrease in the amount of conventional reserves in the world, oil sands are an increasingly important alternative. As the price of oil rises, it becomes increasingly viable to spend money and time converting oil sands into usable raw materials for refining. Unlike conventional crude oil, bitumen requires intense treatment before it can be used. At this stage, Canada is the only country with a large commercial oil sands industry, with 44% of its oil production coming from oil sands in 2007.

Currently only 5% of the known reserves of tar sands are economically viable, this is due to the expense of processing them and the percentage of energy that can be extracted.

There are several ways to extract oil sands, in the huge Athabasca basin surface mining is used. This is because there are very large amounts of bitumen covered for little more. The sands can literally be dug up and transported for treatment. This operation uses the largest electric shovels and the largest dump trucks in the world.

If mining is not a possibility, a variety of on-site systems can be used to extract the oil from the ground. The most common of these is steam-assisted gravity drainage, in this system two wells are drilled side by side, then steam is injected into one of the wells. This head melts the bitumen that makes it flow through the second well. This system allows to recover up to 60% of the oil. Obviously, the energy required to produce the heat and steam makes this production system much more expensive than traditional drilling, but it is successful enough to reduce the cost of developing oil sands to a reasonable level.