Kurt Cobb has an article at Scitizen on a new enhanced oil recovery technique (saying nothing about the greenhouse gas emissions, which are presumably horrendous) - Will Toe-to-Heel Air Injection Extend the Oil Age?.
Currently, the energy for extracting oil from underground must come from the fuel and equipment on the surface. But what if the main source of energy for extracting oil could come from the oil deposit itself? And, what if the method for doing this could provide us with access to oil not amenable to conventional extraction techniques while minimizing disruption of the surface and any associated pollution? This is what the developers of an oil recovery technique called toe-to-heel air injection or THAI suggest they are able to accomplish. And, the technique could increase appreciably the percentage of the world's vast heavy oil resources that we are able to exploit.
The oil the engineers and scientists at Petrobank, the patent holder, have in mind is so viscous that it is not easily budged from its hiding places below the surface. There are other techniques already in use for extracting this oil. But they typically require copious amounts of both water (usually in the form of steam) and energy to work. The THAI process, however, burns some of the oil in the underground deposit in a way that makes the remaining oil flow to the surface on its own through production wells.
This isn't a bonfire, but rather more like a charcoal fire, very hot (400 to 600 degrees C) without flames. Petrobank claims that THAI burns about 10 percent of the oil in place to accomplish its task. The oil is first heated to about 100 degrees C using steam injection. So far this sounds like conventional steam injection technology. But once this critical temperature is reached, the oil is ignited and only air is injected to keep the oil burning. The burning oil creates additional heat which makes the heavy oil flow more easily, and the combustion gases drive the flowing oil toward and up a set of production wells without any pumping. There are other fire flooding techniques. But the particular methods and well configuration of THAI hold great promise for vastly increasing ultimate recovery while minimizing pollution and well failure.
Petrobank claims recovery of between 70 and 80 percent of original oil in place, a truly astounding number. Even if this result proves to be reproducible on a large scale, it won't mean that all heavy oil deposits will be amenable to the THAI process. Some deposits might be too scattered to be economical. Others might not be sufficiently saturated to allow adequate burning and thus high enough temperatures. Yet others might be too close to the surface in which case the fire might break through. Finally, geology, remote location and poor associated infrastructure might make many potential deposits financially too risky to exploit.