Even as they focus on the struggle to plug the leaking oil well in the Gulf of Mexico, engineers are longing for the twisted and scorched metal at the bottom of the sea and other evidence that might tell them what went wrong seven weeks ago.
In recent days, experts from BP have spoken cautiously of raising components of their shattered drilling operation from the ocean floor once the leak is sealed. That could be a distant prospect: officials have warned that the leak might not be plugged until August or later, after BP drills two relief wells. And some potential evidence has been destroyed by the failed efforts to shut down the well.
Still, experts say that some of the equipment, intact or in pieces, will probably be recovered.
Officials seem most intent on retrieving the rig’s blowout preventer, a 325-ton stack of pipes and valves that failed to seal off the well when the explosion occurred on April 20. It is designed to be raised and lowered multiple times, for use on many wells.
“Clearly, you’d want to get the blowout prevention equipment back,” a technical expert from BP, which owns the well, said at a briefing on May 25. “There’s probably going to be a chance to do that.” Under rules laid out by the company, the expert could not be named.
The blowout preventer is supposed to seal off the flow of gas and oil in routine operations and emergencies and has numerous backup systems in case one fails. Investigators have yet to figure out why they did not work.
Subpoena to Transocean
The Coast Guard issued a subpoena on April 30 to Transocean, the rig’s owner, instructing it “to maintain the blowout preventer and to not allow anyone or anything to tamper with it” without the Guard’s permission.
Less certain is the prospect of salvaging all or parts of the Deepwater Horizon rig, which sank two days after the explosion. Some offshore drilling experts suggest that it might be retrieved by attaching new buoyancy tanks with remote-controlled submarines.
Yet the rig is bigger and deeper than anything raised before, making the prospects for recovery a long shot, some experts say.
“Five thousand feet is awfully deep,” said Malcolm M. MacKinnon III, a retired admiral and salvage consultant. “To salvage any part of the rig itself I would think would be very close to impossible.”
“Look at the problem we’re having trying to shut off that oil at 5,000 feet,” said Admiral MacKinnon, who served as chairman of a federal committee that studied ways of improving the nation’s salvage capabilities in case of a terrorist attack.
Information gleaned from the blowout preventer could be used in a joint inquiry, begun on May 11, by the Coast Guard and the Minerals Management Service, an Interior Department agency that is under fire for its role in overseeing offshore oil drilling.
It might also prove vital to the Justice Department in its investigation of any criminal wrongdoing that led to the disaster, and to the independent commission of inquiry created by President Obama and led by Bob Graham, a former senator and governor of Florida, and William K. Reilly, who headed the Environmental Protection Agency under the first President George Bush.
Custody of the blowout preventer could potentially go to the joint investigation of the Coast Guard and the minerals service, said Capt. Ron LaBrec, a Guard spokesman.
“The ultimate disposition of the B.O.P. will be worked out among the various interagency investigating officials,” Captain LaBrec wrote in an e-mail message, referring to the equipment. “Once the B.O.P. is in port, it will be taken to a secure location and maintained as evidence.”
Share of damages?
There is another incentive to retrieve the apparatus: its status could affect negotiations between BP and the blowout preventer’s manufacturer, Cameron International, over who will pay what share of the damages.
One reason the investigators need forensic evidence like this is that workers who might have been the best sources of information about what was known or misunderstood about the well were among the 11 who died in the explosion.
BP has said that it has been denied access to some witnesses — presumably by the witnesses’ lawyers or their employers’ lawyers — a problem that the Justice Department presumably will not have. The panel created by Mr. Obama may decide to provide anonymity to some witnesses, as did the special commission that investigated the 2003 crash of the space shuttle Columbia.
David Nagel, executive vice president of BP, said last month that his company’s investigators had sketched out a sequence of events that might have led the workers to mistakenly conclude that the well was secure before it was sealed with a cement plug before the explosion and fire. But he said the company’s investigators could reach firmer conclusions “as they get more access.”
Enormous objects tend to stay where they land on the seafloor. In 1998, for example, Texaco lost a 3,600-ton part of a platform in the Gulf of Mexico when a cable snapped as it was being transferred from a barge. The company simply gave up on the lost part and had replacement segments built, even though it was in less than 2,000 feet of water.
By contrast, the Deepwater Horizon weighed roughly 10 times as much and is 5,000 feet under the surface. (Its actual weight in water is hard to calculate.)
The record for deepwater recovery may be the partial retrieval of a sunken Soviet submarine by the Central Intelligence Agency in the summer of 1974. The details of that operation remain secret, but reports at the time said it was more than 16,000 feet underwater.
The rig built to haul it up had an 800-ton derrick and three less powerful ones, suggesting a lifting capacity in the low thousands of tons, far too small for the Deepwater Horizon. And the C.I.A. effort was only partly successful: the submarine, which sank after an explosion onboard and was without doubt structurally damaged, broke apart as it was being raised.
BP engineers said some components that might have played a role in the Deepwater Horizon disaster were unrecoverable. They said they had no hope of retrieving anything from within the oil well, like a cement liner that might have failed.
Some evidence is already onshore, like data streamed from the rig to the Houston headquarters of Halliburton, the oil field services company. It shows pressures and flows in charts that, at first glance, look a bit like the ones that emerge from an airplane’s black box after a crash.
Yet the data are fragmentary — one of several reasons that the investigators say they may never produce a complete reconstruction of the actions that led to the catastrophe.
This report, "Raising Remnants of Oil Rig Still on the Agenda," first appeared in the New York Times.