I've already written
about one process for converting Canadian tar sands to usable crude oil without taking up valuable natural gas to cook the stuff; Green Car Congress
has another one such, this time from Petrobank, which has a proprietary means for doing the extraction that involves pumping air into the tar sands, and burning part of it. This causes a large amount of heat, which in turn upgrades and loosens the oil, which is then pumped out. The company estimates that about 80% of the oil trapped in the sands can be removed this way; even more of the crude could be upgraded on the way out using catalytic means.
A thought a couple days later: I wonder, could something similar to this be used on tapped-out conventional oilfields? If two-thirds of the oil is left behind in a regular oilfield, that could be something like 50% more recovery, not too shabby, and without requiring a source of CO2.