that the Athabasca and Orinoco sites (both of similar size) have as much as two-thirds of total global oil deposits. They have only recently been considered proven reserves of oil. This is because oil prices have risen since 2003 and costs to extract oil from these mines have fallen. Between 2003 and 2008, world oil prices rose to over $140, and costs to extract the oil fell to less than $15 per barrel at the Suncor and Syncrude mines. In 2013, crude oil from the Canadian oil sands was expensive oil to produce, although new US tight oil production was similarly expensive. Supply costs for Athabasca oil sands projects were approximately US$50 to US$90 per barrel. However, costs for Bakken, Eagle Ford and Niobrara were higher at approximately US$70 to US$90, according to 135 global oil and gas companies surveyed reported by the Financial Post. Extracting a significant percentage of world oil production from these deposits will be difficult since the extraction process takes a great deal of capital, human power and land. Another constraint is energy for project heat and electricity generation, currently coming from natural gas, which in recent years has seen a surge in production and a corresponding drop in price in North America. With the new supply of shale gas in North America, the need for alternatives to natural gas has been greatly diminished. A 2009 study by CERA estimated that production from Canada's oil sands emits "about 5–15% more carbon dioxide, over the "well-to-wheels" lifetime analysis of the fuel, than average crude oil." Author and investigative journalist David Strahan that same year stated that IEA figures show that carbon dioxide emissions from the tar sands are 20% higher than average emissions from oil. Tight oil Tight oil, including light tight oil (sometimes confusingly the term 'shale oil' is used instead of 'light tight oil') is crude oil contained in petroleum-bearing formations of low permeability, often shale or tight sandstone. Economic production from tight oil formations requires the same hydraulic fracturing and often uses the same horizontal well technology used in the production of shale gas. It should not be confused with oil shale, which is shale rich in kerogen, or shale oil, which is synthetic oil produced from oil shales. Therefore, the International Energy Agency recommends to use the term "light tight oil" for oil produced from shales or other very low permeability formations, while