According to Morgan Downey’s Oil 101, it actually takes more energy to produce a barrel of synthetic crude oil from the oil sands than the barrel of crude contains. Most of that extra energy comes from natural gas. It is worth paying that energy cost because crude oil is a valuable product that can be turned into gasoline, kerosene, etc, whereas unprocessed bitumen laden sand has no value. Note that even more energy is required to run the refineries that turn synthetic crude into usable fuels.
As a result of this, the economic viability of the oil sands depends on natural gas remaining cheap enough for synthetic crude to compete. As such, it is arguably the case the promoting natural gas as a fuel for vehicles and electricity generation is a smart climatic move. It is a relatively clean fuel in those applications, and using it in that way might keep a larger share of it from being used to upgrade bitumen – thus leaving the carbon contained therein safely buried.
In Scenario A (cheap gas), a lot of Canada’s northern natural gas goes towards liquefying and upgrading bitumen, thus liberating the carbon it contains into the atmosphere, both during upgrading and refining processes and when the resultant fuels are burned.
In Scenario B (expensive gas), the natural gas is used for higher-value purposes like electricity generation, and more of the carbon in the bitumen never ends up in the atmosphere. Other forms of environmental damage associated with the oil sands – including air and water pollution, habitat destruction, etc – are also lessened.