[Wonder Warthog]

"Extracting oil from shale is fairly costly from what I’ve read. I’d bet on oil sands being much cheaper."

Well, actually, my comparison was intended to be between oil sands and coal, but oil shale might not be that far off.

I recall reading somewhere some time back an article that Shell had come up with a process for "in-situ" pre-processing. As I recall, they basically drill two wells, run a cable down each, and then impose an electric current, heating the rock, and lowering the oil's viscosity.

Once "thinned" by heat,the oil is then able to flow to a horizontally drilled production well located between the "electrode wells".

[Eric in the Ozarks]

You're correct on both counts. Coal can become oil, but not without a huge investment. We do have 500 + years worth of coal, so we will never actually run out of motor fuel produced one way or another...

I remember an Exxon guy talking about the company's experience with early oil shale technology near Rifle, Colorado. Exxon dug up the shale, crushed it down to the size of golf balls, irradiated it to get the oil, then tried to dispose of the spent gob.
In the process, the golf balls had become tennis balls, so the piles of reject materials were 33 percent larger (and higher) than the original topography.
Nice subject for the Thursday night Sierra Club meeting, eh ?