In northeastern Alberta, Canada are the Athabascan oilsands, third largest oil reserves in the world. They contain bitumen which is found tightly combined with clay and sand. Bitumen has to be separated out by a process (here and here) requiring great quantities of water at high heat, which, in turn, requires burning fuel and producing greenhouse gases. The resulting very thick bitumin can be transported to refineries and ports by rail, or it can be mixed with a diluent, a hydrocarbon, so it will flow through pipelines.
Large stretches of arboreal forests in the Athabascan have disappeared in the pursuit of the bitumen, replaced by open pit mines.