The 12 November 2007 issue of the New Yorker includes an article called Unconventional Crude by Elizabeth Kolbert. When I checked the site, the article was not available electronically. This may change as the issue is superceeded by subsequent issues, so check the site if you are reading this in subsequent weeks. Regardless, here is an interesting snippet from the article.

In 1956, an American geologist, Manley Natland came up with the idea of streamlining the process by using atom bombs. Natland reasoned that “thermal devices” could be lowered into the limestone beneath the tar sands and exploded. This would create cavities into which the bitumen, heated to more than a thousand degrees would flow and from which it could then be collected. The idea was taken seriously at the highest levels in both Ottawa and Washington—the United States Atomic Energy Commission even agreed to supply a bomb to test Natland’s theory—but it was never implemented.

Beginning in the mid-nineteen-sixties, the Soviet Union actually tried the experiment, setting off half a dozen nuclear explosions to stimulate conventional oil production; production increased, but, unfortunately, much of the oil turned out to be radioactive.