The largest sized vessel that can dock in Vancouver is an Aframax, which can carry 500,000 to 700,000 barrels. Vessels at the port can only be loaded up to 80% due to depth and other restrictions, meaning a vessel can only be filled to around 550,000 barrels. That's a stark contrast to one million barrel Suezmaxes, or the two million very large carriers (VLCCs) commonly used to ship crude oil from Saudi Arabia, the Middle East and African countries to Asia and other countries around the world, including Canada (e.g. The Irving Oil refinery in N.B.). Most vessels that currently load in Vancouver go to refineries in Washington State, California or Hawaii. Traders said the price of Canadian crude shipped to Asia needs to be low enough to offset the cost of shipping across the Pacific on smaller vessels. They also note many Asian refiners prefer Iraqi crude due to lower acidity.
(source: Canada oil sands Asia export dream faces port bottleneck, GulfNews.com)