In the Gulf of Mexico, what went wrong with the Deepwater Horizon oil drilling rig?
http://www.washingtonpost.com/wp-dyn/content/article/2010/05/08/AR2010050803429.html
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.
He looked at the rig and saw an astonishing spectacle: A geyser of water and mud shooting to the top of the 242-foot derrick at the center of the rig.
Then came the gas, a furious hiss from the earth. Seconds later there was a green flash, an explosion, a fireball. The muddy geyser became a blowtorch. Of the 126 people on the rig, 115 escaped the inferno, but 11 simply vanished, their bodies never recovered. Deepwater Horizon burned for two days. On April 22, the 40th anniversary of the first Earth Day -- founded in response to the Santa Barbara oil spill of the previous year -- the 396-foot-long, 256-foot-wide rig sank to the bottom of the gulf.
What went wrong?
A target of the investigation, according to Rep. Ed Markey (D-Mass.), who chairs the House energy subcommittee and met with oil company officials last week, is the final cementing job on the well. Four employees of Halliburton -- founded by Erle Halliburton in 1924 as the Halliburton Oil Well Cementing Company -- were on Deepwater Horizon. They had overseen the main task of cementing the well just 20 hours before the blowout.
This is done by plunging a slurry of cement down the hollow pipe to the bottom of the well, where the cement passes through a one-way valve, then rises back up through the narrow gap, or annulus, between the steel casing and the rock walls of the hole. This stabilizes the casing in the drill hole and keeps gas and oil from rising through the drill hole to the surface.
Or at least that's the idea. If something goes awry, such as cracks forming in the cement or the cement failing to set properly, gas bubbles can seep upward, and the pressure can begin to build toward calamitous proportions.
Kenneth Deffeyes, a professor emeritus of geology at Princeton who has studied reports of the blowout, said it's possible that "the cement job wasn't heavy enough and the gas bubbled up through it." But, he added, another factor could have been a malfunction of the valve, or "shoe," at the bottom of the well, which could have let gas and oil into the steel casing.
Deepwater Horizon was almost home free after several months of drilling the Macondo field. Its job is to drill an initial well to find a reservoir, temporarily seal the well and move on, leaving the oil production to other rigs. Before Deepwater Horizon could leave the site, it had to drop two pre-formed cement plugs into the well. The crew had placed one plug in the well when the blowout occurred.
A petroleum engineer whose name is not public, but who called the Mark Levin radio show in New York and is now represented by New Orleans attorney Scott Bickford, has given an account of what happened in the final moments before the blowout, according to a report in the New Orleans Times-Picayune. He said that the heavy drilling mud was pulled from the well and replaced with lighter sea water before the second cement plug was put in place. According to Bickford, this lowered the resistance to the natural pressure of the well, and a bubble of gas surged upward.
"The well kicked, and we took a humongous gas bubble kick up through the well bore," said the engineer in the call to the radio show. He said he didn't know whether human negligence played a role in the accident. Geological forces surely did, he said.
"You're dealing with 30 to 40,000-pound per square inch range. It's serious pressures," he said. "It just seems like every now and then you can't win against Mother Nature. She throws you a curveball that you're not prepared for."
BP, which leased the rig, and Transocean, which owned it, have released few details about that night and have not corroborated various accounts of the accident that have appeared in the news media.
Whatever happened with the cement, the mud and the plugs, there was supposed to be a fail-safe mechanism: the blowout preventer. This massive apparatus has multiple valves that can close the well, plus a pair of blind-shear rams that can slice right through the pipe in an emergency.
Survivors say they hit the red button on the rig to activate the system. The device also has a "dead man's" switch that should have worked when the well erupted even if there was no manual signal from above.
Although some media reports have focused on the rig's lack of an "acoustic trigger," another mechanism for remotely activating the blowout preventer, it seems unlikely to have made a difference. BP officials think the blowout preventer partially closed the pipe, because a full loss of well control would have created a leak 10 times greater in volume -- a gusher. Even with robotic submarines subsequently manipulating the control panel at the sea bottom, BP's technicians couldn't get the device to work properly.
Markey said during a tour of the oil spill Friday, "I think it's a little bit premature to reach a firm conclusion, but there is obviously an issue with the cementing process. There is an issue with the overall failure rate of blowout preventers over the years that has not received the highest level of safety attention that it should have."
The depth of the leaking well hampers not only the attempts to cap it, but also the efforts to find out what went wrong. The blowout preventer may be a culprit, but it can't be yanked to the surface because it may be serving a critical function in impeding the leak.
One line of attack would be to place another blowout preventer on top off the existing one, said Doug Suttles, BP's chief operating officer. A second option would be a "junk shot" -- injecting material into the blowout preventer to clog it up and shut down the flow of oil. But BP wants to avoid any rash moves that could backfire.
"We didn't want to take any action that could make the spill worse," Suttles said.
Almost home free
An oddity of the disaster was the timing. What puzzles industry experts is that the most hazardous part of the operation, the initial drilling of the well, had been completed without incident. Deepwater Horizon was almost home free.
"They had the least unknowns about the well than at any other stage in drilling the well," said Bruce Bullock, director of the Maguire Energy Institute at Southern Methodist University. "They knew what the pressures were, they knew what the temperatures were, they knew what the depth was. They'd already gone through all that."
Charlie Williams, chief scientist for oil engineering and production technology at Shell Oil, which has pioneered much of the deepwater drilling, said the industry has had an excellent track record of success beyond the continental shelf. Oil companies, like airlines, he said, have powerful incentives to maximize safety.
"We have a huge vested interest in the safety of the rig, the safety of the crew, the safety of the environment and the safety of the resource," he said. "We go to great lengths to make sure that these devices work. We want it to be very rare that you have to make use of the blind-shear rams to stop flow from the well."
Deffeyes, the Princeton professor, said, "Here we have the statistically unlikely case of both systems failing." The blowout is one failure, the blowout preventer's malfunction is the second, and there may even be a third failure, he said -- for example, if the steel casing was improperly attached to the blowout preventer.
"Murphy's Law: If anything can go wrong, it will," Deffeyes said.
Which raises the most ominous scenario for the industry: That there was no single, dramatic failure of technique or technology or human vigilance. Instead, the industry may simply have miscalculated the risks of drilling in the more highly pressurized deepwater reservoirs, said Nansen Saleri, president and chief executive of the technology firm Quantum Reservoir Impact.
"The frontiers of exploration have been pushed out to far more complicated and contentious environments," Saleri said. "There is a need to take a fresh look at the whole thing."
Said analyst Byron King, "This is the oil industry's Chernobyl."
Staff writer David A. Fahrenthold and staff researcher Madonna Lebling contributed to this report.
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