BP seek solution after oil spill setback
Updated on 09 May 2010
Methane ice crystals halt BP's attempt to stem the flow of oil gushing from its well in the Gulf of Mexico. Methane too may have been the original cause of the fire.
The huge, 93 ton, steel and concrete box that BP had hoped to place over the leaking pipe from the well head has been moved 200 metres to one side while engineers decide what to do.
As they lowered it into position, a sludge of methane ice crystals began forming in the top of the box, clogging the hole where BP had hoped to fit a pipe to take the oil to a ship on the surface.
The methane comes from the oil itself, dissolved in it in the pores of the rock beneath the sea bed.
Indeed, methane may have been the cause of the original fire.
Professor Robert Bea from the University of California Berkeley, a former engineering consultant to BP, says he has seen transcripts of interviews with three survivors of the blast on the Deepwater Horizon rig. They say a gusher of oil and water spurted out of the top of the drill pipe on the rig as a bubble of methane gas rose up the drill column from the depths.
Alarms designed to warn of the highly flammable gas failed to go off, they said, and the huge cloud of invisible, odourless methane enveloped the rig and was ignited, perhaps by a spark from electrical equipment or motors.
Professor Bea believes the transcripts suggest the methane gas may have formed as rig workers tried to cement a seal on the well head. As the cement sets in an exothermic chemical reaction, it gives off heat, which may have warmed the oil enough to release the dissolved gas, which then exploded up the pipe, bursting the seal.
At the time, BP executives were aboard the rig, owned by Transocean, celebrating its safety record. They are reported to have suffered a number of serious injuries.
BP has refused to comment, but a spokesperson told me: "We have always said the oil there was very gassy."
Because of that, BP had anticipated that methane might hamper their bid to capture the oil with their giant box. But they admit the problem is worse than they had thought.
The dissolved methane separates from the oil as it spews out of the leaking pipe on the seabed with a sudden drop in pressure. But at the cold temperature and pressure of the sea floor, 5,000 feet deep, the methane doesn't form bubbles of gas, it forms very light, slushy ice crystals that would normally float up towards the surface.
But BP's big box trapped them. They are so light they made the box buoyant and BP told me they were also having difficulty holding the 93 ton box down on the seabed as the methane tried to lift it like a balloon.
Fifteen years ago, I joined a research drilling ship with my colleague Andy Veitch, to search for methane hydrates in the seabed off Bermuda. As cores of sediment came up from the drill methane hydrate showed up as white clumps in the mud and as soon as they were exposed to the air they fizzed and disappeared as they melted.
It will take at least 48 hours for BP engineers to come up with a solution.
One idea is to somehow heat up the oil and water mixture in the box to melt the methane crystals. Another is to pump methanol down into the box to dissolve them.
Meanwhile, 5,000 barrels a day of oil continues to gush out.
