CALGARY — Within two years, half of Canada’s total crude oil output will come from northern Alberta’s oilsands, representing 10 per cent of North American production, according to an energy survey released Monday. The PricewaterhouseCoopers survey of Canada’s top oil and gas companies and energy trusts also predicts that offshore exploration in Atlantic Canada will continue despite recent high-cost drilling disappointments. Oilsands development has grown dramatically over the past five years with investments totalling more than $15 billion, according to the survey. ‘‘Oilsands have little exploration risk associated with them, and the potential for them to become a major source of oil became more evident in 2002 when North America’s share of global reserves increased from five per cent to 18 per cent,’’ said Raymond Crossley, a member of the firm’s energy and utilities practice. ‘‘This reflected a dramatic rise in reserves of heavy oil in oilsands deposits.’’ Last year, the Oil and Gas Journal, an authoritative industry publication, finally recognized 177 billion barrels of reserves from the oilsands. This makes Canada the second-largest holder of energy reserves in the world behind Saudi Arabia. And it dwarfs the amount of remaining Canadian conventional oil, which in Alberta is only about 1.6 billion barrels. The PricewaterhouseCoopers study places the oilsands reserves even higher, at an estimated 2.5 trillion barrels of bitumen in the ground, of which 315 billion barrels can be recovered with current technology and pricing. This latest proof of the rising status of Canada’s oilsands in North American energy production comes as Shell Canada (TSX:SHC) prepares to officially open its $5.7-billion Athabasca Oilsands project this week. Athabasca, owned 20 per cent by Chevron Canada and 20 per cent by Western Oil Sands Inc. (TSX:WTO), is the third major open pit oilsands mine, behind industry pioneers Suncor Energy (TSX:SU) and Syncrude Canada. It is also a pivotal year for the oilsands as several large North American energy producers, including Calgary-based Nexen (TSX:NXY) and U.S.-based Devon Energy and ConocoPhillips, are poised to decide whether to proceed with their individual steam-assisted oilsands plants. Go-ahead decisions depend on an array of issues, including the unknown costs of adhering to the Kyoto climate change protocol, as well as global factors like the volatile price of oil. Many of the projects also require financing, says Crossley.