Extracting More Energy From Old Oil Wells

First, via peakoil.com, the US Department of Energy claims 43 billion barrels of recoverable oil could be reclaimed using new CO₂ injection methods.

Carbon dioxide enhanced recovery involves flooding a mature oil reservoir with large volumes of carbon dioxide. But there are actually two distinct recovery techniques using carbon dioxide — miscible recovery and immiscible recovery.

The miscible technique works with high-gravity oil. Carbon dioxide from an injection well mixes with water and oil in the reservoir to form a single, relatively low viscosity fluid phase that flows out through a production well.

The immiscible technique applies to reservoirs with relatively low gravity oil or with low reservoir pressures — in these situations the carbon dioxide does not mix with the oil but, instead, reduces the viscosity of the oil through swelling of the fluid. The pressure of carbon dioxide forces the oil out through the production well.

These methods could be made to work in domestic U.S. fields in onshore fields in California, Louisiana, Texas, Alaska, and Illinois, and offshore in the Gulf Coast and Louisiana. With Alaska, however, the problem is getting a CO₂ stream to the oil fields. Gosh, if they're having a hard time finding CO₂ sources, I can think of a few...

The second bit is a piece in FuturePundit about applying microorganisms in depleted oil wells to generate natural gas. LUCA Technologies has discovered that the same microorganisms that convert coal to methane are much more effective when applied to depleted oil wells. This process was thought to occur over geologic timespans, but recent research indicates it can happen in real time and in significant amounts. The FuturePundit article has a lot of good info on it which I'm not inclined to duplicate here; best to read that instead.