sentences:  Although the promise of the oil sands deposits has been clear for more than a century, oil production from the Suncor and Syncrude oil sands plants did not become profitable until well after the 1979 energy crisis.Despite comparatively high oil prices in world markets, for political reasons government kept prices for oil from these technological pioneers at artificially low levels until well into the 1980s.In recent years, oil sands and heavy oil development have been so successful that these resources now account for more than half of Canada's crude oil production.