Flows through the UK's most important oil pipeline, Forties, have recovered to around half the normal rate, a trading source said today.

This suggests a steady return to normal operations after a rare unplanned shutdown. 

The closure since December 11 of the pipeline, which normally pumps about 450,000 barrels per day, and supply disruptions in Libya have helped push oil prices above $67 a barrel, their highest since mid-2015. 

Ineos, the pipeline's operator, restarted the flow earlier in the week and has pledged to resume full volumes in early January. Ineos could not immediately comment on current flow rates today. 

"It's a slow ramp up, but it's about half the normal rate," the trade source familiar with the operations said. 

Forties plays an important role in the global market as it is the biggest of the five North Sea crude streams underpinning Brent, a benchmark used for oil trading in Europe, the Middle East, Africa and Asia. 

The system, which also carries a third of Britain's offshore natural gas output, was shut down after a crack was found. 

Oil companies that pump into the pipeline, including Royal Dutch Shell, were restarting oilfields that had to be shut during the repairs.

Buzzard, Britain's largest oilfield, was producing over half its normal level, a trade source said.

Ineos was forced to declare force majeure on deliveries of Forties crude oil, natural gas and condensate, suspending its contractual obligations to customers by citing circumstances beyond its control. 

This is believed to be the first force majeure on a major North Sea production stream in decades. 

Ineos did not say when it expected to lift the force majeure. 

Ineos, a privately-owned chemicals company based in Switzerland, bought the pipeline system from BP in late October.