Mining for Petroleum

Although Mining Engineering and Petroleum Engineering are two different fields of study, the two fields cross paths when it comes to the Oil Sands Industry. Oil Sands refers to the deposits of petroleum in the form of heavy bitumen being present in a mixture of sand or loosely consolidated sandstone. Because this heavy oil is too thick to flow and because it is thoroughly mixed with sand, the conventional methods of extraction of petroleum by drilling cannot be applied here. For this reason and also if the oil sand deposit lies relatively close to the surface, open pit mining is used to extract the oil sands. Once mined, the sands are processed to produce synthetic oil.

The mining for oil sands begins like in most mines by the overburden removal process. Common machinery such as excavators, bucket scrapers, and bulldozers are used to remove the overburden and the overburden is hauled by trucks and piled separately for refilling purposes. Once the overburden is removed and the oil sand layer exposed, the mining process begins. Since the oil sand deposits are unconsolidated, they can be easily be extracted by shovels or excavators. For this reason and for obvious safety reasons blasting is not performed. In addition to these machines, draglines and sometimes continuous excavators such as bucketwheel excavators are also used for mining the oil sands. The mined sand is hauled to a plant where the petroleum is extracted and refined by a variety of processes including crushing, froth flotation and distillation.

Although previously termed as an unconventional source of petroleum, the depletion of "conventional oil" and the associated rise in oil price has resulted in a shift of attention towards the oil sands industry. The largest oil sands deposits are located in Canada and Venezuela and the total volume of oil contained in the sands exceeds the conventional oil reserves of the world.  Oil sands have been commercially extracted in the Athabasca region in Canada since the 1930s and since have developed along with the advances in extraction technology. The following graph shows the value of sales  of oil sands and conventional crude oil in Canada and it can be seen that the oil sands sales have shown a significant rise during recent years.

value of sales of crude oil and oil sands (data taken from : http://www.capp.ca/library/statistics/Pages/default.aspx)

New methods have been developed to extract oil sands deposits that are too deep to extract using surface mining. These methods involve the reduction of the viscosity of the bitumen and the separation from the sand and enables the oil to be pumped to the surface. These methods are termed "In-situ methods". Cyclic Steam Stimulation (CSS), Steam Assisted Gravity Drainage (SAGD) and Toe to Heal Air Injection (THAI) are some of these methods. With advances in in-situ methods like these, the the recovery percentages of oil sands deposits have increased and now it can be considered as a viable alternative to conventional oil.