Extracting oil from shale is fairly costly from what I’ve read.
I’d bet on oil sands being much cheaper.
In any case, I think Keystone got US government endorsement yesterday.
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".