I've read several published sources indicating that the oil reserves in the tar sands region of northern Alberta are substantial enough to maintain current levels of consumption in North America for 500 years. The major problem was getting it out -- Suncor developed an extraction method back in the 1980s that allows them to
mine it (as opposed to
drilling it) for about $12 per barrel, and the area around Fort McMurray has experienced a tremendous boom over the last two decades. As time goes on, the problem is that the oil will be more difficult to extract. The oil sands are between two layers of the earth's crust that angle down from the surface, and as time goes on it will be necessary to extract it from greater depths.
In addition to these issues, you have to keep in mind that Saudi oil is much more "pure" and does not require much refining, while tar sands oil is about as crummy as it gets and must be refined extensively.
Appreciate that info- it jogs my memory; that's about what I recall reading a month or so ago.