I was kind of thinking the same thing: Big Oil isn’t stupid. Tom, a Ph.D. in Mechanical Engineering writes:
There might be something to be gained from using the heat energy from unused oil wells, but I’m guessing not, or the oil companies probably would have done it already. These kind of power systems are pretty well developed by now, so it wouldn’t have been hard for them to do. Again, it mostly depends on fuel costs being so high that the expense of the system is offset by the fuel savings over the plant life.
I’m not familiar with the MIT study mentioned — there is a lot of geothermal energy, but the sources that are close to ground level are few and far between, and it’s fairly easy to suck so much energy out of them that they cool down — not so useful if you need reliable electricity. If deep wells were cheaper, then you might have something.