Almost no one is in much doubt that conventional oil reserves are finite and the time must come when we can no longer rely on them as a source of world hydrocarbons. I note that oil has hit almost $110 a barrel, up from $106 just a few days ago and more than five times its price five years ago. In the face of rising costs, an inevitable depletion in supply and a dependence on regions of the world the West would prefer not to be too dependent on, oil shale is being touted as a blanket solution to these problems. There are many predictions that even if existing markets are maintained, demand for oil will exceed its supply within 5 - 10 years, which really is just tomorrow in the sense of implementing alternative technologies that are not already underway.
Oil sands are underway, notably at Athabasca in Canada, and there are various estimates of how much "oil" can be extracted from them, but it will not be more than a few percent of the 30 billion barrel annual bill for oil worldwide, and rising inexorably. Oil shale is a far less well developed technology, even though it is said that there is a greater reserve of oil held within these rocks than lies under the sands of Saudi Arabia and the Middle East all-told. Oil sands are demanding in terms of the other resources, i.e. gas and water, that are needed to produce oil from them. "Tar-sands" is a more descriptive term since they contain not oil but bitumen, which must be recovered from a large excess of earth and rock "sands", which yield around a final barrel or two at most of oil per tonne. From an environmental perspective, not only is pressure placed on an ultimately limited recovery of these other resources but the procedure is dirty and leaves a considerable stain on the local regions. To get around the problem of using natural gas to heat water with which to drive bitumen from the material, it has been proposed to build two nuclear reactors at Athabasca, as an alternative heat source, which has pleased the environmentalists even less. I wrote about this in the posting "Nuclear Powered Oil Sands".
I accept that we can't have it both ways, i.e. to consume energy at our present rate and not place pressure on the environment. Our most pressing needs are to produce electricity and also liquid fuels for transportation, both of which place their own burden on the Earth. In my opinion, it is the latter that is most urgent since although electricity can be made from various sources, fossil fuel, nuclear, hydro and in principle other renewables too, if we can get the appropriate infrastructure working within a pressingly short timescale, keeping transportation running, at least in the short term, does need liquid fuels. The hydrogen is a long way off, even if all the problems attended to it can be solved - an M.I.T. study reckoned optimistically that even with assiduous research and development there will not be hydrogen cars before 2020 - and by then we will nave plunged into the Oil Dearth Era, as I have called it, in which transportation and hence many familiar and globalist aspects of our way of living have been severely curtailed. [Electric transport, tram systems and stand-alone electric/PHEV vehicles would take massive efforts and much time to implement, too]. Coincidentally, Biomass-to-Liquids (BTL) technology is not expected to be operating commercially before 2020 either, and then only on a relatively small scale in comparison with the quantity of petroleum-based fuels that will be needed to maintain transport momentum.
So, are oil-shales the answer? As with the tar/oil sands, shale does not contain oil but is a rock known as marl which contains primordial organic material, such as kerogen. When this is heated to around 450 degrees C in a process called "retorting" (because the material is heated in vessels called retorts), the result is a hydrocarbon material which can be refined in similar fashion to crude oil to generate transportation fuel. So, that's the good news. Indeed, a pilot-plant in Queensland Australia thus produced 700,000 barrels of oil during the period 2001 - 2003, so it does work.
Overall, however, the process is highly polluting because the "oil" is very dirty, laden with sulphur compounds and so on, with impacts on the air and groundwater. I note that the heavier conventional crude oil is also far less sweet to deal with than the light crude, production of which peaked a couple of years ago, and so refining this conventional resource will be more demanding certainly in terms of energy than has hitherto been the case.
Since oil-shale requires a lot of heat to generate from it a usable liquid fuel, the EROEI (Energy Returned on Energy Invested) is considerably lower than it is to recover fuel from conventional oil. The yield of synthetic crude from shale is lower than it is from oil sands, at around one barrel for each two tonnes of rock that is processed. Each barrel of oil from shale also needs three barrels of water to produce it, i.e. about the same as from tar-sands, which adds up to a lot of water. Notably, much water in the US used for agriculture, certainly in the south and the west, is actually fossil-water, i.e. pumped up from underground aquifers and not replaced by rainwater. Hence this resource along with gas might be considered finite, depending on its precise origin and point of use. Shell is developing an alternative technology of "in situ retorting" where the shale is heated in the ground without being dug-out, for 3 - 4 years at 400 degrees C, which they claim can produce oil at a mere $30 a barrel and in the present face of oil prices this does look attractive, at least economically.
If oil-shale is to be exploited on a serious scale, it will demand considerable engineering and that will take time to install, so much so that many analysts feel that the technology will not arrive fast enough to close the imminent 5-10 year window during which conventional supplies of oil will fall against world demand for it. Taken at face value, the amount of "oil" that might be recovered from oil-shale, oil/tar-sands, tar sludge (which sounds charming), heavy crude and coal is enormous, perhaps enough for 100 years or more, according to some estimates. The heat source for in situ retorting is provided from electric heaters, so that electricity has to be made somewhere. An alternative is "nuclear oil" which I think would require actual mining of the rock and retorting it using the heat generated from nuclear reactors, probably of the pebble-bed type, and such installations could be built in proximity to shale deposits, tar sands or sludge to coax oil from them.
It is argued that "nuclear oil" is clean, following that argument we often hear that nuclear is non-polluting in terms of CO2 emissions, ignoring issues of nuclear waste and indeed the "cleanliness" of processing materials of this kind per se. There is also the issue of limited uranium supplies which we will get through more rapidly if we expand nuclear power for whatever purposes. It is a very difficult matter. No one wants to run out of oil, in Europe and certainly in the US where covering huge urbanized distances routinely (as James Howard Kunstler has written about in "The Long Emergency") depend utterly on supplies of cheap fuel. All of us in the global village depend, even if not for personal travel, on goods that have been brought over considerable distances, of course possible only if cheap oil is available in the quantity we are now used to. It has also been suggested that nuclear explosives could be used to break-up oil-shale underground to aid its exhumation for retorting.
That such measures are being seriously considered is a clear demonstration of desperation. Oil supplies are going to fail and sooner not later. Given the limited timescale, I simply don't see how we can implement "nuclear" or other kinds of unconventional oil in sufficient amount to take up the slack from conventional production - even if this is deemed desirable - on that 30 billion barrel annual equivalent scale. O.K. we won't need to replace all of that in one go, but the ramping-up of unconventional production as the former declines will be no trivial effort, and again I can only foresee a rapid decline in that 700 million vehicles on the road as there are now; ignoring the rising demand for fuel by aviation, which in the UK consumes almost one quarter of all fuel used here. Globalism will fade while "localism", involving a way of life based around small communities beckons from the near horizon.