The platform was not producing when the collision occurred at 1:55 a.m. on Friday (2355 GMT on Thursday), and there were no injuries to the 276 people on the platform, the company said.

The platform has been shut since the end of May for maintenance expected to last through July, an Equinor spokesman said.

It was too early to say whether the maintenance would have to be prolonged as a result of the incident, he added.

Staff were evacuated by helicopter to nearby platforms while Equinor investigated the extent of the damage, which included harm to the lifeboats.

"We have supported Equinor with helicopters. There is no risk to life on the platform," a spokesman for the rescue coordination centre for southern Norway said.

The supply vessel, the PSV Sjoeberg, was heading to land unassisted, with 12 people onboard, Equinor said.

Statfjord is operated by state-controlled Equinor with a 44.3% stake, while ExxonMobil holds 21.4% and the rest is held by two units of Spirit Energy, data from Norway's Petroleum Directorate shows.

Statfjord, which opened in 1979, is among the oldest fields still producing in the North Sea.

(Reporting by Nerijus Adomaitis and Gwladys Fouche; Editing by Dale Hudson)