In the Gulf of Mexico, what went wrong with the Deepwater Horizon oil drilling rig?

Oil companies stress one another's failures in a Senate hearing as cleanup and containment efforts continue in the Gulf of Mexico, after the explosion of the Deepwater Horizon oil rig April 20.
By Joel Achenbach
Washington Post Staff Writer
Sunday, May 9, 2010

Deepwater Horizon was true to its name. The giant drilling rig, floating on submerged pontoons, set up shop 42 miles from land in the Gulf of Mexico. It was an award-winning rig that epitomized the technological hubris of the oil industry, successfully chasing the hydrocarbons far beyond the continental shelf in what can accurately be termed the abyss.

The drilling of Mississippi Canyon Block 252 this spring looked like an unqualified success. The rig struck oil and gas beneath 5,000 feet of water and 13,000 feet of rock. Executives of BP planned to make a splashy announcement. The Macondo field, as they called it, held 50 million to 100 million barrels of crude.

Then came the blowout. The gulf is now witnessing a slow-motion disaster, one that looked even grimmer Saturday with the bulletin that the containment dome that had been lowered onto the worst of the oil leaks has been sidelined by technical problems.

No one is sure what exactly happened on the night of April 20 to trigger this crisis. Critical pieces of evidence, including the immolated rig itself, sit under nearly a mile of water on the mud floor of the gulf.

What's certain is that more than one thing had to go wrong. Some failure of well control permitted a bubble of gas to surge to the surface, where it ignited and turned Deepwater Horizon into a Roman candle in the night. Moreover, the fail-safe mechanism known as the blowout preventer, a massive stack of valves and pistons that is the most critical hardware in the system, failed to choke the well.

There have been blowouts since the dawn of the oil drilling industry, but never a blowout like this. This one is the deepest on record, industry officials say. A blowout last August in the Timor Sea had some similarities, but it was in much shallower water. Capping the unsealed well, said Coast Guard Commandant Adm. Thad Allen, is as tricky as getting the Apollo 13 astronauts home safely in their damaged spaceship.

"We have gone to a different planet in going to the deepwater. An alien environment," oil industry analyst Byron King said. "And what do you know from every science fiction movie? The aliens can kill us."

To extract hydrocarbons from the ground, even on land, is to take on powerful terrestrial forces. The oil and gas are in hot, porous rock, under pressure and trapped -- until someone sticks a straw into the reservoir. The deeper the well, the higher the pressure.

Engineers talk of the importance of having multiple layers of controls, or "barriers," when drilling. They don't pump the oil up, because they don't need to. Instead, they shove heavy drilling mud, a synthetic goo, into the well to act as a counterweight to the pressure from below. As the ultimate layer of defense they install the muscular blowout preventer with its hydraulic shears that can cut right through thick pipe.

But sometimes nature is harder to tame than expected. The consequences of a blowout can be dire in shallow water. At great depth, the consequences are only now, with each passing day, becoming fully apparent.

A geyser, a hiss, a flash

Something dirty was falling from the sky -- that's what Alwin Landry, captain of the supply ship Damon B Bankston, remembers of the night of April 20. "Just a dirty rain," he recalls. The stuff spattered the back half of his boat, which floated just 40 feet from Deepwater Horizon.

"What is this," Landry said to a crewman. The skipper figured that a line had busted and was leaking drilling mud.

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