Gulf Spill: Did Pesky Hydrates Trigger the Blowout?

Dick writes about Earth and planetary science for Science magazine.

Methane-trapping ice of the kind that has frustrated the first attempt to contain oil gushing offshore of Louisiana may have been a root cause of the blowout that started the spill in the first place, according to University of California, Berkeley, professor Robert Bea, who has extensive access to BP p.l.c. documents on the incident. If methane hydrates are eventually implicated, the U.S. oil and gas industry would have to tread even more lightly as it pushes farther and farther offshore in search of energy.

Drillers have long been wary of methane hydrates because they can pack a powerful punch. One liter of water ice that has trapped individual methane molecules in the "cages" of its crystal structure can release 168 liters of methane gas when the ice decomposes. Bea, who has 55 years of experience assessing risks in and around offshore operations, says "there was concern at this location for gas hydrates. We're out to the [water depth] where it ought to be there." The deeper the water, the greater the pressure, which when high enough can keep hydrates stable well below the sea floor.

And there were signs that drillers did encounter hydrates. About a month before the blowout, a "kick" of gas pressure hit the well hard enough that the platform was shut down. "Something under high pressure was being encountered," says Bea—apparently both hydrates and gas on different occasions.

Workers from Halliburton who had just pumped cement into the well to temporarily seal it off were well aware of the potential hydrate hazards, says Bea. Halliburton just last year had developed strategies to avoid having the heat of curing cement decompose any nearby hydrates and trigger a kick, he says. A special foamy cement was used to seal the well this time. It was just after the seal was tested that natural gas drove through it, a malfunctioning blowout preventer, and a drill pipe full of seawater to ignite on the platform, killing 11 and eventually sinking it. "There are so many operations like this around the world," says Bea. "My hope is we'll use this disaster as an opportunity to take a step forward" in risk reduction.

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