The operator of the Maari oil field off the coast of Taranaki is to begin an upgrade of its floating production station the Raroa in March.
OMV said the $60 million project will future-proof the vessel's mooring system.
Managing director Peter Zeilinger said the work had been scheduled to coincide with the annual maintenance shutdown and to take advantage of lower servicing prices.
The upgrade will involve work on eight mooring lines, which are permanently anchored to the sea floor.
Minor oil spills have been reported at the production station in February last year and in October and November of 2010.