James Hamilton expresses doubts about oil shale.
The fact that large quantities of heat are required to obtain a usable fuel from the rock means that this is a far less efficient source of energy than conventional oil. Shell claims it can produce 3.5 units of energy for every unit input, though one wonders whether the energy content of all the inputs is taken into account in such figures. The lower this ratio, the more the cost of producing oil from shale would rise as energy prices go up. Another implication of the high energy needs for processing is that significantly more greenhouse gases are released per barrel of usable fuel produced. Concerns about greenhouse emissions appear to have been the basis on which Greenpeace succeeded in closing down the Australian demonstration plant.
It would be interesting to try to draw up a timeline for various alternative energy sources. What strikes me about shale oil, and also to some extent about new nuclear power, is that by the time they can be brought on stream, solar power or some other alternative may be superior. But at least with nuclear power, we know that the process does not use up more fossil fuel energy than it replaces.