Monday, September 05, 2005

A new source of oil?

The United States has by far the largest fossil fuel deposit in the world. The Green River Basin in Colorado contains several times as much oil as Saudi Arabia, but it's in the form of oil shale, a mix of rock and organic compounds from which it is very difficult to extract the useful oil.

According to this extremely optimistic column in the Rocky Mountain News, Shell has come up with a way to extract this oil that will be profitable at $30/barrel. (Oil is currently almost $70/barrel.) It supposedly yields 3.5 units of energy for every unit consumed. Here's how Shell says it works:

Shell's method, which it calls "in situ conversion," is simplicity itself in concept but exquisitely ingenious in execution. Terry O'Connor, a vice president for external and regulatory affairs at Shell Exploration and Production, explained how it's done (and they have done it, in several test projects):

Drill shafts into the oil-bearing rock. Drop heaters down the shaft. Cook the rock until the hydrocarbons boil off, the lightest and most desirable first. Collect them.

Please note, you don't have to go looking for oil fields when you're brewing your own.

On one small test plot about 20 feet by 35 feet, on land Shell owns, they started heating the rock in early 2004. "Product" - about one-third natural gas, two-thirds light crude - began to appear in September 2004. They turned the heaters off about a month ago, after harvesting about 1,500 barrels of oil...

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).

Obviously this could be great news if it was true. I'm still somewhat skeptical. If the project was really as far along as the article implies, I would have expected to hear about it from larger, more significant news sources than a column in the Rocky Mountain News. On the other hand, we've been completely overwhelmed with news these past few days and it's certainly plausible that it would be ignored in the frenzy surrounding Katrina, the Rehnquist retirement, etc.

The article also doesn't look at all at what potential problems with the process might be. For example, one failure of previous oil shale extraction technologies was that they required a lot of water, and American shale is all located in a very dry part of the country. You can't tell from the article whether the Shell process is less water-intensive than previous processes. There's also the environmental problems--how hard is it to clean the water once you're done with it? It would probably be a mistake to think that these problems have easy solutions just because they're not mentioned in the article.