Shell: Oil Shale Economical At $30/Barrel?
the process should be commercially feasible with world oil prices at $30 a barrel. The energy balance is favorable; under a conservative life-cycle analysis, it should yield 3.5 units of energy for every 1 unit used in production. The process recovers about 10 times as much oil as mining the rock and crushing and cooking it at the surface, and it's a more desirable grade. Reclamation is easier because the only thing that comes to the surface is the oil you want.If this works out, it could be huge. I wonder that similar processes couldn't be used in mining the Athabascan tar sands.
And we've hardly gotten to the really ingenious part yet. While the rock is cooking, at about 650 or 750 degrees Fahrenheit, how do you keep the hydrocarbons from contaminating ground water? Why, you build an ice wall around the whole thing. As O'Connor said, it's counterintuitive.
But ice is impermeable to water. So around the perimeter of the productive site, you drill lots more shafts, only 8 to 12 feet apart, put in piping, and pump refrigerants through it. The water in the ground around the shafts freezes, and eventually forms a 20- to 30-foot ice barrier around the site.
Next you take the water out of the ground inside the ice wall, turn up the heat, and then sit back and harvest the oil until it stops coming in useful quantities. When production drops, it falls off rather quickly.
That's an advantage over ordinary wells, which very gradually get less productive as they age.
Then you pump the water back in. (Well, not necessarily the same water, which has moved on to other uses.) It's hot down there so the water flashes into steam, picking up loose chemicals in the process. Collect the steam, strip the gunk out of it, repeat until the water comes out clean. Then you can turn off the heaters and the chillers and move on to the next plot (even saving one or two of the sides of the ice wall, if you want to be thrifty about it).