NewScientist: Uncontrolled methane gas blowout from Elgin-Franklin wellhead platform does not contain sulphur

No toxic hydrogen sulphide in North Sea gas leak

by Michael Marshall, NewScientist, March 28, 2012

Some good news from the beleaguered Elgin platform leaking gas into the North Sea: the gas is not laced with deadly hydrogen sulphide as originally feared. That means that the ecological impact of the spill could end up being relatively minor.

"We now know the gas is not toxic," says a spokeswoman for Total, the platform's owners, although it is not clear how the company has come to that conclusion.

The leak began on Sunday, and is coming from a newly disturbed source in the rock above the original reservoir. The source is approximately 4,000 metres down, about 1,500 metres above the reservoir of sour gas – natural gas laced with hydrogen sulphide – that the platform was extracting, but which has been closed for over a year.

Total still does not know how much gas has escaped, how fast it is escaping or how much is in the source reservoir. A surveillance plane overflew the area at 8 a.m. U.K. time, today, and confirmed that there is a sheen of condensed gas and mud on the surface of the sea, with a volume of roughly 30 cubic metres.

Firefighters on hand

The surveillance also confirmed that there is a visible gas cloud, which is heading east driven by prevailing winds. There is still a lit flare atop the platform, which was left on when the platform was evacuated to dispose of excess gas. However, the gas cloud is apparently being carried away from the flare, and is also tens of metres below it.

"We are quite confident that the flare shouldn't pose a threat," the Total spokeswoman says. Two fire-fighting vessels are on hand.  [Mad dogs and Englishmen.  Oh wait.  Total is a French company.]

Total has not yet decided what to do, and a planned survey of the seabed using a remotely operated vehicle has not been carried out.

The company says that there is some chance that the leak will stop of its own accord. If that does not happen, Total may airlift well-control experts onto the platform, to perform a "kill operation" to plug the leak.

Alternatively, it could drill a relief well – but that could take up to 6 months.

http://www.newscientist.com/article/dn21637-no-toxic-hydrogen-sulphide-in-north-sea-gas-leak.html