By 2045 oil sands will produce close to 11M bbls/d and that will continue for a century. Between 2012 and 2020 oil output from the tar sands will double (1.7 mbpd --> 3.4 mbpd) and triple in the next 25 years to 5.1 million barrels per day.
With crude oil fetching higher prices in Asia, Canadian producers are looking to expand into new markets (nearly all Canadian oil (2M bbls/d) currently heads south, 2010). (Reuters:Foes fight Canada pipeline to rich Asia market) The supply chain has, more recently been overwhelmed in the United States due to the release of 30M barrels of reserve oil onto the market Parkersburg News and already filled up pipelines and storage tanks. With China's interest in Canada growing, the 728 mile Northern Gateway pipeline from Edmonton to Kitimat, BC is gaining the attention of politicians and oil companies eager to broaden their customer base.Ironically, environmentalists are both helping and hampering efforts to provide access for Asia; The oil pipelines face fierce opposition from environmentalists and Native Indian groups concerned over wildlife and possible oil spills (like what happened with Enbridge in Michigan in 2010); at the same time American environmental groups have opposed the oil sands on the grounds that it makes excessive use of water and increases greenhouse gas emissions.
Keystone XL, another oil pipeline struggling through the approval phase, aims to bring more of Canada's oil to the United States in an effort to reduce their dependency on Middle East oil 'potentially to nil'. Among other top sources, Mexico is an unsustainable source due to dwindling reserves there and Saudi Arabia (number 2) is viewed as unstable due to its situation within the Middle East. TransCanada's $7 billion pipeline project would double Alberta's oil exports to the United States. Though Obama rejected the permit in January 2012 he didn't completely shut the door on the project, saying that the company is free to re-apply. Whether or not the project goes ahead one thing is for sure, Alberta will continue to produce oil. As of last summer there were 22 active exploration projects in Athabasca alone.
The reason that it's 52% even though all of Canada doesn't have half of the world's oil is that, much of the new oil being discovered/produced is heavy-extra heavy oil and a lot of it is in countries like Venezuela which don't allow foreign investment/ownership of their state run oil companies. Even in Colombia where capitalism is as popular as it has ever been, big oil companies like Ecopetrol remain off limits to foreign investors (in August Ecopetrol (majority state owned) will have its biggest share sale since 2007 in which it will make available between 3 and 5% of Ecopetrol shares but only Colombian citizens are allowed to participate).