OIL giant Shell has shut down production on its Shearwater platform as it was revealed that it could take up to six months to quell the uncontrolled leak of toxic, volatile gas at the nearby Total Elgin installation.
The energy giant announced plans to suspend production on the Shearwater as North Sea union leaders called for the platform to be completely evacuated because of the risk of a Piper Alpha-type disaster posed by the presence of a massive cloud of explosive gas over the Total installation, just 4.6 miles away.
As the “substantial” gas leak continued unabated on the Elgin platform, bosses at the French oil giant were continuing to examine a series of options to bring the escape under control.
Two oilrigs have already been put on standby to drill a relief well, which could take at least six months to complete.
Two specialist firefighting vessels, the Skandi Saigon and the Sea Bear, have also been deployed to the area by Total.
Shell had taken the first steps to stand down part of the workforce on its Shearwater platform and the nearby Hans Deul drilling rig, 138 miles east of Aberdeen, on Monday night because of the cloud of highly flammable gas shrouding the Elgin installation.
Initially, 52 workers on board the Shearwater were flown to Aberdeen, leaving 28 still on board, while 33 personnel on the Hans Deul were evacuated, leaving 73 still on board.
Yesterday, Shell announced that a further 35 workers had been flown off the drilling rig, leaving only 38 on the Hans Deul.
However, by early afternoon the oil major said: “Further to the precautionary safety measures we took yesterday following Total’s gas leak at Elgin, we have now brought forward plans to carry out maintenance at Shearwater.
“This will take place from today, starting four days ahead of schedule. We are therefore shutting down production in a controlled manner.
“Drilling operations on the Noble Hans Deul rig have been suspended and the wells have been left in a safe state.”
Wullie Wallace, the Unite regional officer, claimed Shell’s actions did not go far enough, and called for the Shearwater and any other installation within a five-mile radius of the drifting gas cloud to be fully evacuated and powered down.
“This incident cannot be underestimated in its seriousness, and there is still a clear and present danger, we believe, to many of our members while the drifting gas issue continues,” Mr Wallace said.
“While we welcome the speedy evacuation of the Elgin, and the fact that two further installations in the immediate vicinity have been down-manned of all non-essential staff, we are concerned that only partial evacuation has taken place on the other installations in the area so far.”
He added: “We would be looking for full evacuation of any platforms within five miles of the Elgin and for the power to be switched off on these installations also.
“The risk may be low, but our concern is that if the drifting gas was to hit any of the neighbouring installations, the results could be catastrophic.”
Jake Molloy, regional organiser of the RMT union, also warned of the potential for a major disaster, like that on the Piper Alpha rig in 1988, in which 167 workers were killed.
He said: “The potential exists for catastrophic devastation at that installation [Elgin]. You have got a free-flowing well and they can’t stop it. If it does somehow find an ignition source, you could be looking at the complete destruction of this installation.
“This is an unprecedented situation and we really are in the realms of the unknown, but the urgent need now is to find a way of stopping the flow of gas. God willing, they get in there and kill this well sooner rather than later.”
Exclusion zones of two miles by sea and three miles by air, established by the Maritime and Coastguard Agency, remained in force yesterday as Total enlisted the advice of well-control experts from across the globe, including legendary “Hellfighters” Boots & Coots.
David Hainsworth, health, safety and environment manager for Total, admitted that the gas leak could go on for months. One estimate is that it could be leaking at a rate of 2kg per second.
Mr Hainsworth explained that the company was looking at a number of options to stem the flow of gas.
He said possible solutions including drilling relief well which would take a minimum of six months to complete or to kill the rogue well once it was considered safe enough to allow personnel back on board the installation.
He revealed that Total was now convinced that the source of the leak was on the platform and not subsea.
“We have two or three eyewitness statements from people who were on the platform at the time of the incident and they have given us consistent stories as to what they have seen, which is a release from the conductor pipe just below the wellhead on the platform,” he said.
He continued: “We are evaluating a range of options. Clearly, the best case is that this just dies a death on its own over a period of time.
“The reservoir is not productive, but there is gas there. We are trying to ascertain how much gas might be down there, and we have geoscientists working on that.”
• Possible outcomes
1 The leak stops of its own accord as it runs out of gas to feed it. Total believes the gas feeding the leak is coming from a non-productive reservoir higher up in the formation.
2 Drilling another well to relieve the pressure on the reservoir. This was the solution used to stem the flow of oil and gas following the Deepwater Horizon disaster in the Gulf of Mexico. However, the relief well could take at least six months to complete.
3 Deploying well control teams to the platform once it is safe to do so. One method would be to “kill” the well by packing it with heavy mud. Another method is known as a “dynamic kill”, which would involve circulating fluid inside the well to create a hydrostatic column that would stem the leak.
North Sea’s biggest disasters
• July 1988 – 167 oil workers were killed in the Piper Alpha disaster, the world’s worst ever offshore catastrophe, following a massive gas leak and inferno on the Occidental-operated platform.
• September 1988 – The drilling rig Ocean Odyssey was devastated by a series of explosions and fireballs in a high pressure gas blow-out that claimed the life of radio operator Timothy Williams.
• April 2005 – Oil giant Shell was fined a record £900,000 for safety failings on the Brent Bravo platform that led to the deaths of two workers, killed by a gas escape.
• August 2011 – Divers finally shut off the leaking oil valve on the subsea pipeline at the centre of the North Sea’s biggest oil spill for a decade – several hundred tonnes – nine days after the emergency on Shell’s Gannet Alpha platform began.