Serica Energy said it had been informed by operator BP that the Bruce, Keith and Rhum fields have each resumed production following the successful repair of the Forties pipeline system.
The fields were shut in on December 11, along with all the other fields using the system and have been brought back into production as part of a phased restart of the pipelines.
In November, Serica announced that it had agreed to acquire interests in the fields from BP, subject to certain regulatory, government and partner consents.
The deal had an effective date of January 1 and completion of the acquisition is expected to take place in mid-2018.
At 9:56am: (LON:SQZ) Serica Energy PLC share price was +1.3p at 91.7p