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May 8, 2010

Methane hydrate build-ups sideline BP cofferdam

"This dome is no silver bullet," said U.S. Coast Guard Rear Adm. Mary Landry, the federal on-scene coordinator for the Deepwater Horizon spill response, at a press conference this afternoon.

The dome is, of course, the cofferdam lowered to contain oil gushing from the Deepwater Horizon well site. It is now sitting on the seafloor as BP tries to figure out a way of dealing with methane hydrate crystals that formed a slush within it.

The "icing up" of the cofferdam with the crystals has put methane hydrate into the public spotlight for the first time. As investigations of the Deepwater Horizon catastrophe continue, deposits of methane hydrate seem likely to emerge as presenting one of the biggest challenges facing deepwater drilling technology.

The buildup of methane hydrate slush made the cofferdam too buoyant and clogged it up, BP chief operating officer Doug Suttles told the press conference. After it had been carefully lowered over the leak nearly a mile below the surface, it had to be raised and moved 200 meters to the side as means to manage formation of the crystals were deliberated.

Options might include finding some means of providing heat at the seafloor level, or applying methanol.

Something else that is being considered is a "junk shot." This, said Mr. Suttles would involve taking "ground up materials of various types" and attempt to inject it at the bottom of the blowout preventer to plug the leak in an operation that Mr. Suttles compared to stopping up a toilet.

Another option being looked at is to place a second blow out preventer atop the failed one.

As these developments unfolded, reports emerged that implicated gas liberated from methane hydrates as a likely cause of the explosion and fire that destroyed the Deepwater Horizon.

Robert Bea, a University of California Berkeley engineering professor who serves on a National Academy of Engineering panel on oil pipeline safety, has received copies of interviews with survivors of the explosion and has described them to the Associated Press.

Essentially they describe a sequence of events in which a bubble of methane gas escaped from the well and shot up the drill column, expanding quickly as it burst through several seals and barriers before contacting an ignition source and exploding.

The well was being sealed and a chemical reaction caused by heat from the setting cement may have released methane.

The interviews described by Professor Bea were reportedly taken as part of BP's internal investigation.

Another interview that is openly available is a call from by a survivor to talk radio host Mark Levin. It gives detailed insights into the operations being undertaken on Deepwater Horizon prior to the explosion. It is in two parts, both of which deserve careful attention and both of which are available HERE.

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