The UK authorities will grant French oil company Total permission in the next few days to proceed with plans to staunch the leaking well on its North Sea Elgin gas field, industry sources said on Sunday, a day after a dangerous flare blazing above the Elgin production platform went out of its own accord.
Total wants to launch two processes in parallel to stop the gas leak from the well. Those dual strategies will put the well - which is emitting potentially explosive gas - out of commission, at least temporarily, but the company cannot proceed without a green light from Britain's Health and Safety Executive (HSE).
If Total passes a risk assessment by the HSE it can then proceed with stopping the leak.
Authorisation for both options should land early next week, perhaps on Monday, one of the sources said.
Commenting on the risk assessment, an HSE spokesman said: That process is ongoing. I cannot comment on timelines.
The flare that had been burning only 100 metres from where the gas is leaking was finally extinguished on its own without intervention on Saturday, reducing the threat of explosion.
Attention has now shifted to getting on with stopping the leak.
In the first process, Total will inject drilling mud to kill the well using the weight of the mud to stop the gas flow, but is potentially dangerous given that it would require workers to return to the wellhead platform.
The second process - safer, but slower and costly - involves digging two relief wells, which could take six months and cost up to $3 billion.
Relief drilling would require boring down 4 kilometres to intercept the gas pocket at exactly the right point, engineers say.
Total had originally hoped the leak would run itself dry as reservoir pressure dropped, removing the need to bore a hole.
But the discovery that the source is just 1.5 kilometres away from the main gas reservoir, one of the world's deepest, suggested that the amount of gas feeding the leak may be larger than first thought.
FLAME IS OUT
The gas flare, which had been lit as part of the initial emergency response to relieve pressure on the well as workers were evacuated, had been causing concern that it might ignite the leaking gas. But the UK Department of Energy said that Total had assured it that the prevailing winds were blowing the gas away from the flare. The leak, which started a week ago, has been spewing an estimated 200,000 cubic metres a day of natural gas into the air, forming a potentially explosive gas cloud around the platform.
It began after pressure rose in a well that had earlier been capped.
Total evacuated its 238 platform workers, and set up a two-mile exclusion zone for safety reasons, with fire-fighting ships on standby.
A senior union official said on Friday that Total had repeatedly assured workers a leak was impossible until just hours before evacuating them.
(Editing by Alexandria Sage and Greg Mahlich)