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Relief wells, 'heavy mud' plug being tried to stop North Sea gas leak

By the CNN Wire Staff
March 31, 2012 -- Updated 0206 GMT (1006 HKT)
Large volumes of gas continued Friday to gush into the North Sea from an offshore oil platform.
Large volumes of gas continued Friday to gush into the North Sea from an offshore oil platform.
STORY HIGHLIGHTS
  • Total's Elgin platform in the North Sea began leaking gas on Sunday
  • Currently, about 200,000 cubic meters of gas a day are leaking into the water
  • Two methods are being tried to stop it: drilling relief wells and plugging it up
  • A Scottish official says the environmental risk appears to be minimal

(CNN) -- Large volumes of gas continued Friday to gush into the North Sea from an offshore oil platform, with energy giant Total trying two divergent methods in hopes of stopping the leak.

Scottish Environment Secretary Richard Lochhead said Friday that authorities are prepared for the worst, but he added that it is believed that the "gas condensate" now flowing into the water "will evaporate naturally into the atmosphere."

"As such, the current environmental risk continues to be minimal," Lochhead said.

The Elgin platform sprang a leak Sunday, prompting the evacuation of 238 people from the platform and the adjacent Rowan Viking drilling rig, according to Total executive Philippe Guys. The leak seems to have started as workers were sealing the well in the North Sea, about 150 miles (240 kilometers) east of the Scottish city of Aberdeen.

Since then, energy company and government officials have weighed what to do about it, with one option being waiting for the gas to stop leaking on its own.

A waiting game over Elgin gas leak
Major gas leak in the North Sea

On Friday, one day after announcing it had pinpointed the source of the leak, Total detailed its dueling approaches to stop it: blocking the outflow with "heavy mud" (consisting of a mixture that contains mineral compounds) and drilling a pair of relief wells.

Until then, "the leak remains ongoing," according to Guys. Gas is now gushing into the North Sea at an estimated rate of 2 kilograms per second, which translates to about 200,000 cubic meters per day.

The North Sea was the scene of the world's worst offshore rig disaster, the Piper Alpha explosion, which killed 167 people in 1988.

The Elgin leak has echoes of the BP oil spill in the Gulf of Mexico in 2010 -- including the fact that both emerged as workers were closing off wells -- but there are differences.

The Elgin is in shallower water than the BP spill, which could make problems easier to fix. And instead of oil, it is leaking gas, which can disperse faster but ignites more easily.

"This is nothing on the scale of the Gulf spill two years ago," oceanographer Simon Boxall said. "This is a relatively light spill. The gas itself is dispersing quite rapidly."

After Total's share price fell sharply earlier in the week, it rebounded slightly on Friday with a 0.9% gain.

Guys, the executive from the energy giant, said Friday that "all other" Total wells in the vicinity are in "safe condition," signaling that there is no expectation of further problems.

Shell has also partially evacuated two of its nearby platforms, Shearwater and Hans Deul, as a "purely precautionary" measure, it said Wednesday.

Satellites and spotter planes are being used to assess the latest spill, while several vessels are on standby nearby ready to help, Guys said.

Lochhead, Scotland's environmental minister, said he was "pleased" that "more information" on the incident had been released by Total and the British government.

While expressing faith that the long-term impact on the environment shouldn't be major, Lochhead said that the hard work is far from over.

"We cannot be complacent, and Marine Scotland is continually assessing the situation and scenario planning for all eventualities," Lochhead said. "Additional scientific resources, manpower and vessels can be utilized at short notice, should the situation change."

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