Norwegian energy giant Equinor will keep the Safe Boreas accommodation vessel at the Mariner field for another month.
Equinor, formerly Statoil, has exercised a one-month extension option for the second time.
The total value of the option is £4.7 million for Cyprus-headquartered vessel owner Prosafe.
In early August 2017, the Safe Boreas commenced a 13-month firm operational period at Mariner in the UK sector of the North Sea, which will now continue through to early November 2018.