CO2 Injection  

The Oil Drum has a post up on increasing efficiency of oil extraction using CO2 injection. There are a few caveats - as I noted a while ago, you need to be on land - you also need to be near a CO2 source, such as a power station.

One of the more promising techniques for EOR is injecting carbon dioxide into a layer of rock that still has oil, but where it cannot easily be obtained normally. There are two benefits to using CO2. One of these is to strip some of the gas out of the atmosphere. The University of Texas recently showed that they could inject liquid CO2 into a depleted oil reservoir, and because the reservoir was a fluid trap, it would hold the gas and keep it from getting back into the reservoir.

But the benefits extend beyond that. An experiment that the Globe and Mail referred to has been going on in the Weyburn oil field in Saskatchewan for the last five years. CO2 from a synthetic fuel plant in North Dakota is piped to the oilfield and injected. While the reservoir holds the gas, the mix with the oil, means that the oil flows out of the well more easily.