Buried Treasure


Gauging the (natural) gasSay "hi" to hydrateFreezing, but not coldUsing hydrateWarming worries



RIGHT: This spinning methane molecule ...

See "Animations... " in the bibliography) Animations for Petroleum Systems: 36 Short MPEG Movies, Howell, David G., et al. U.S. Geological Survey, 1999.


Gas 'er up!
Enough of the theory. What stands in the way of using this enormous resource? Nobody has ever deliberately drilled gas hydrate (although one Russian gas well has apparently tapped them by accident).

still taken from animation of spinning methane moleculeAs land-lubbing, oil-grubbing consumers, we must say tapping hydrate sounds suspiciously easy. You drill a hole, melt the ice, and pipe out the natural gas.

In the real world, experts assure us it's a bit more complicated. They say three methods might be used, either alone or in combination.

1. Reduce the pressure. High pressure raises the freezing point of the water in gas hydrates, allowing them to exist above 0 C. Drilling into the hydrate would reduce pressure, allowing the ice to melt, liberating methane.

2. Raise the temperature. Injecting steam from the surface or raising hot fluids from below the gas hydrates could also melt hydrate.

3. Inject chemicals. These, like salt on your driveway, would melt the ice.

Dillon of the USGS told us that cost and other limitations indicate that depressurization is likely to be the first method tested in the field. But melting could cause chaos, he adds: "If you destabilize gas around the drill pipe, you could have a collapse or a landslide," he says. "You are softening up the ground down under."

The problem is twofold: liberating the gas increases pressure, and melting weakens the hydrates. The result could be topsy-turvy drilling rigs - a painful prospect given their hefty price tags.

Getting the stuff out of the ground will be a real challenge, says Sassen of Texas A&M. Existing methods, he says, may work on "a little test case in Alaska or Japan, but if you got something a mile across, or 10 or a thousand miles across, you've got a completely different infrastructure to think about."

All gassed up and nowhere to go?
Sassen advocates a reality check on gas hydrate. There may be, as some claim, more gas in the Blake Ridge - an area the size of Rhode Island - than in all the continental United States. "But none of it is economic," he argues. "It's so thinly dispersed over a large area, also it's in three kilometers of water."

Furthermore, he adds, the hydrocarbon layers are too shallow to emulate present-day oil drillers by branching out from a single well horizontally from it.

Sassen says the energy industry, fueled by Wall Street's demand for immediate profits, prefers dealing with mother lodes - what the oil patch calls "elephants." In gas hydrate, he says, "Where you do see elephants, focused and localized masses that are really thick, is in the Gulf of Mexico."

And that, he says, is where the first serious exploitation of gas hydrates is likely to occur.

Methane is a hefty greenhouse gas. Should we worry?


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