Deep Horizon blowout caused by 'methane bubble'

News reports from this past weekend indicate that the Deep Horizon drilling rig disaster was caused by a methane bubble that traveled up the drill column. The details in the AP story are not completely clear, but it seems that exothermic heat released by curing cement caused a significant amount of methane, which exists on the ocean floor in the form of slushy, heavier-than-water crystals, to warm up enough to convert to gas phase and begin traveling up the drill column. From that point, the laws of physics took over as the methane encountered decreasing external pressures and increasing temperatures as it rose through the column:

As the bubble rose up the drill column from the high-pressure environs of the deep to the less pressurized shallows, it intensified and grew, breaking through various safety barriers, [Robert Bea, a University of California Berkeley engineering professor] said.

“A small bubble becomes a really big bubble,” Bea said. “So the expanding bubble becomes like a cannon shooting the gas into your face.”

Up on the rig, the first thing workers noticed was the sea water in the drill column suddenly shooting back at them, rocketing 240 feet in the air, he said. Then, gas surfaced. Then oil.

“What we had learned when I worked as a drill rig laborer was swoosh, boom, run,” Bea said. “The swoosh is the gas, boom is the explosion and run is what you better be doing.”

The gas flooded into an adjoining room with exposed ignition sources, he said.

The greatest bit of irony about the accident is that occurred on the day that BP executives and officials were holding a party aboard the rig to celebrate it’s outstanding safety record during the exploration phase of operations:

“That’s where the first explosion happened,” said Bea, who worked for Shell Oil in the 1960s during the last big northern Gulf of Mexico oil well blowout. “The mud room was next to the quarters where the party was. Then there was a series of explosions that subsequently ignited the oil that was coming from below.”

According to one interview transcript, a gas cloud covered the rig, causing giant engines on the drill floor to run too fast and explode. The engines blew off the rig and set “everything on fire,” the account said. Another explosion below blew more equipment overboard.

… The BP executives were injured but survived, according to one account. Nine rig crew on the rig floor and two engineers died.

“The furniture and walls trapped some and broke some bones but they managed to get in the life boats with assistance from others,” said the transcript.

The reports made Bea, the 73-year-old industry veteran, cry.

It also seems clear that for whatever reason, the three redundant safety features that were installed on the drill column all failed to work:

Blowouts are infrequent, because well holes are blocked by piping and pumped-in materials like synthetic mud, cement and even sea water. The pipes are plugged with cement, so fluid and gas can’t typically push up inside the pipes.

Instead, a typical blowout surges up a channel around the piping. The narrow space between the well walls and the piping is usually filled with cement, so there is no pathway for a blowout. But if the cement or broken piping leaves enough space, a surge can rise to the surface.

There, at the wellhead of exploratory wells, sits the massive steel contraption known as a blowout preventer. It can snuff a blowout by squeezing rubber seals tightly around the pipes with up to 1 million pounds of force. If the seals fail, the blowout preventer deploys a last line of defense: a set of rams that can slice right through the pipes and cap the blowout.

Deepwater Horizon was also equipped with an automated backup system called a Deadman. It should have activated the blowout preventer even if workers could not.

Based on the interviews with rig workers, none of those safeguards worked.

Unfortunately for the whacked-out minions of Daily Kos, Firedoglake, and Democratic Underground, this appears to have been a very tragic and costly accident, and nothing more.

Deep Horizon was a unique oil drilling rig, operating hundreds of miles off shore and drilling in water a mile deep. It also utilized a state-of-the-art motorized, satellite-controlled positioning system instead of being moored to the sea floor by anchors. The engineering feats required to position any floating platform over a tiny spot in the floor of the sea and actually drill an oil well are truly impressive. The engineers who design these systems design them to achieve a maximized combination of performance and safety. BP certainly had reason to celebrate what had been, up until the time of the accident, an extraordinarily successful venture.

We would be wise to wait until further investigations reveal more information about the events leading up to the blowout, before making any more snap judgments about who is responsible and why. Instead, let’s pray for the souls who were lost and their families, and hope that the well can be capped as soon as possible.

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