SINGAPORE, May 8 (Reuters) - New Zealand Refining Ltd's 135,000 barrels-per-day Marsden Point oil refinery has returned from a partial shutdown and is operating normally, a company spokesman said on Tuesday.
He did not specify how long the unit was shut for or when it returned from maintenance, but added that customers had to import petroleum products to meet demand during the shutdown.
"We are now back to production and successfully supplying our major oil company customers, there has been no change to our refinery run rate as a result of the shutdown and capacity remains at 135,000 barrels a day," spokesman Greg McNeill said in an emailed statement.
The shutdown had minimal impact on the diesel market, with just a few cargoes seen headed there, traders said.
Shareholders in New Zealand Refining, which is the operator of the country's only oil refinery, approved in late April a major upgrade project to improve production and increase margins.
Construction of the continuous catalyst regeneration platformer (CCR) project is expected to take three years to complete, with the CCR unit operational in late 2015.
The expansion is expected to lift production of petrol by around two million barrels a year and increase New Zealand Refining's share of New Zealand's petrol demand to around 65 percent.
The company currently supplies around two thirds of New Zealand's refined fuels and related products, including more than half its petrol, 80 percent of diesel, and virtually all aviation fuel.
It is around 73 percent owned by the four major oil companies in the country, BP, Mobil Oil NZ, Caltex NZ, and Greenstone Energy Ltd, a joint venture between Infratil Ltd and the state NZ Superannuation Fund, which bought Shell Oil's local retail operations. (Reporting by Jessica Jaganathan: Editing by Nick Macfie)