The New Zealand Refining Company is considering investing up to half a billion dollars to replace its ageing petrol-making plant at Marsden Point.
The move could add up to 300 jobs to the region.
The country's only refinery wants to boost its share of the fuel market from about 50% to about 80%.
Chief executive Ken Rivers says it will carry out a $23 million study to examine how cost-effective the investment will be, amid an expected surplus of petrol stocks in the region.
He says the report should be ready for the board to cosider by this time next year.
The refinery more than doubled its annual profit to $57.6 million in the year to the end of December due to improved refining margins as demand picked up.
Revenue rose 16% to $291 million with economic growth in China and India, a rise in diesel demand in the Asia-Pacific region and reduced refining capacity boosting margins to $US6 per barrel.
New Zealand Refining declared a dividend of 10c a share, on top of the first half payout of 2c a share.
The company, which supplies about 80% of the country's refined fuels, charges a processing fee for refining crude oils and feedstocks.
It is 73% owned by BP, Mobil Oil, Caltex and Greenstone Energy.
