Plans in place to counter North Sea gas leak

FOLLOWING confirmation that a fire on Total’s Elgin platform has extinguished itself, the company is actively preparing to regain control of a leaking well. On March 25, the company reported that gas had started leaking from its wellhead platform in the offshore Elgin gas field in the North Sea, about 240km east of Aberdeen, UK.
Total EP UK managing director Philippe Guys said at a press conference in Aberdeen that the company had first observed irregular pressure in the annuli on the plugged G4 well in the Elgin field on February 25. “We very quickly moved to kill the annuli pressure by pumping it full with high-density mud,” Mr Guys said. “During this process, on March 25, we observed a sudden pressure increase followed by an escape of mud and then gas. This was released below the wellhead at deck level on the platform – not subsea [level].” Mr Guys said that the main producing reservoir in the G4 well, at about 5500m depth, had been plugged for more than a year. “The leaking hydrocarbons are believed to be coming from a rock formation above (at a depth of 4000m below the seabed),” he said. “This tight formation at high pressure is not a producing reservoir in the Elginfield; however, it contains a non-toxic gas which could have migrated to the annuli.” Mr Guys said that based on recorded data and reservoir modelling, Total estimated the leakage rate to be about 2kg per second (equating to about 200,000 cubic metres per day).
Once the flare on the Elgin platform was extinguished, Total launched two main action plans to stop the leak. First, the company reported that it planned to carry out well control operations using a floating support vessel, and pumping mud into the well. Total stated in an April 2 announcement that this solution required workers to reboard the platform, and the company was working to ensure that regaining access would be undertaken in safe conditions.
Total also announced that it was sourcing the necessary support vessels to facilitate the well control operations. “Two suitable vessels have been chartered – one boat and one rig. Each of the vessels identified has special dynamic positioning capability, making them most suitable for the operation planned,” the company stated. Total’s second action plan related to drilling a relief well and a backup relief well. To drill these wells, two rigs are in the process of moving to Elgin after final suspension of their current operations: Sedco 714 is currently drilling on the Fettercairn field, 400km north of Elgin; and the Rowan Gorilla V rig is only 6km from Elgin, drilling on the West Franklin field. Total also stated that other drilling rigs were being considered, “to maintain the widest possible range of options”. Two other key vessels are also standing by on site – a remotely operated vehicle used to carry out underwater inspections, and a similar vessel for conducting seabed surveys to determine possible locations for relief wells. Total reported that the site was continually being monitored by aircraft and firefighting vessels.
Mr Guys commended the prompt and safe evacuation of the 238 people on the Elgin platform at the time of the incident. “I would like to stress the very deep regret which I personally, and everyone at Total, is feeling over the incident at the Elgin complex. Our top priority, as always, is the safety of our personnel,” he said. Mr Guys also responded to queries about why workers were being kept on the nearby Franklin wellhead platform. “The answer is because they can offer valuable assistance with the monitoring of the situation and, at a distance [of] more than five kilometres from the Elgin platform, we consider them to be in no danger. “If we did, they would have been instantly removed,” Mr Guys said.

 

By Danica Newnham

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