Here's an excerpt explaining some of the perils to unconventional oil:
Producing unconventional oil is not only unconventionally expensive but also unconventionally destructive. To access the up to 200-feet-deep “feed” of oil sands, Shell and its competitors must ﬁrst dispose of a layer of forest—mostly jack pine, ﬁr, and birch—that they refer to as overburden. Two barrels of fresh water are required to produce each barrel of synthetic crude, and some 5 percent of the bitumen extracted by Shell and other companies mining the region’s oil sands ends up in tailing ponds toxic with mercury, napthenic acid, and other contaminants. The tailing ponds put the lives of migrating birds at risk and, should they leak into other bodies of water, those of other creatures as well. Many people suspect that the high incidence of cancer reported in the town of Fort Chipewyan has something to do with its location downstream from major oil-sands operations.