Canada is the world's fifth-largest oil producer, and only Saudi Arabia and Venezuela have more proven reserves of crude. Almost all of Canada's reserves (and production) are in the form of oil sands, which are among the most expensive types of crude to produce. Now the Canadian oil sands producers have to contend with an even greater opposing force: economics. But a few things play to their favor. The first is that their costs are more akin to a mining operation than conventional oil drilling. Oil sands projects require massive upfront investments, but once those are made, they can go on producing for years with relatively low costs. That's made oil sands, and the companies that produce them, quite profitable over the past few years. That cost structure may give oil sands producers an advantage over frackers in the US, who operate on a much shorter time horizon. Canada's falling dollar could end up benefiting its oil sands producers.