BP has sold off several oil fields in the North Sea for £475m.
Premier Oil said it was buying five fields in the Andrew Area and the Shearwater site – both around 140 miles from Aberdeen.
It said it wanted to capture the 82m barrels of oil and equivalents thought to still be trapped under ground.
A total of 69 BP workers will transfer to Premier under the deal.
Ariel Flores, BP North Sea regional president, said: “BP has been reshaping its portfolio in the North Sea to focus on core growth areas.
“As a result of this focus, we have also now decided to divest our Andrew and Shearwater interests, believing them to be a better strategic fit for another owner.
“We are confident that Premier Oil, already a significant operator in the North Sea, is the right owner of these assets as they seek to maximise their value and extend their life.”