Oil Sands

 Fort McMurray Oil Sands, Canada

From Wikipedia:

However, the world's largest [oil sands] deposits occur in two countries: Canada and Venezuela, each of which has oil sand reserves approximately equal to the world's total reserves of conventional crude oil.

In numbers:

Conventional crude reserves: 1.75 trillion barrels
Canadian + Venezuelan oil sand reserves: 3.6 trillion barrels

It isn't clear if these reserves are those at a given price, eg today's $90 per barrel, or not.