Increasing energy demands and pressures on Conventional Light Oil “CLO” of the Eastern Hemisphere (85% of the global inventory) have shifted the focus to Unconventional Heavy Oil “UHO” and Conventional Tar Sands “CTS” deposits around the world. The major part of “UHO” is in the Western Hemisphere (69% of the inventory), mainly the USA, while the majot part of “CTS” is being found in Canada. We have to keep in mind that the world inventories of UHO” and “CTS” may, indeed, exceed the global inventories of “CLO”.

Unconventional oil sources and oil sands are created in the same way as conventional oil—that is, through the combination of organic material, heat, and pressure. The main difference between the two is their ability to move underground. Conventional oil migrates upward due to its buoyancy. This oil moves through pathways in the underground rock in its fluid state and becomes trapped between impermeable layers of rock. Unconventional oil and oil (tar) sands, meanwhile, is formed in sealed spaces of rock, or being mixed with sand, and is not able to move up; it therefore remains in the source rock/sand, trapped in pores or unconnected pores. Unconventional oil and oil or tar sands are therefore produced and extracted using techniques other than conventional method used in Conventional Oil industries. Governments across the globe are investing in unconventional oil sources due to the increasing scarcity of conventional oil resources. 

Due to the different nature of accumulation and existence in underground formations and difficulties associated with production/extraction of unconventional oil and oil sands there are multiple of additional environmental threats and climatic impacts. Production and extraction of unconventional oil and oil sands consume much more water, have enhanced negative impacts on the environment in terms of produced waste, contamination and pollution especially what regards degradation of aquatic life, eco-systems and bio-diversity. Moreover, carbon dioxide emissions from the production and extraction of unconventional oil and oil sands are relatively higher, up to 20%. Indeed, the climatic and environmental (http://blogs.worldwatch.org/revolt/unconventional-oil-implications-for-the-environment-and-greenhouse-gas-emissions-2/) impacts of unconventional oil and oil sands are not fully understood and consequence assessment analyses are fragmentary, incomplete and far from being representative especially what regards the large-scale and long-term impacts and threats.

http://www.greenparty.ca/sites/greenparty.ca/files/attachments/a_comprehensive_guide_to_the_alberta_oil_sands_-_may_2011_-_last_revised_march_2012.pdf