In a statement to the market, the gold producer said total proven and probable gold reserves of 3.64 million ounces of gold and 240,000 tonnes of copper as of December virtually offset 2012 mining depletion.
Of this, proven and probable reserves in New Zealand, where the company operates the Reefton, Macraes and Frasers mine, total 51.8 million tonnes grading 1.17 grams per tonne gold for a contained 1.95Moz.
Meanwhile, in the Philippines, proven and probable reserves at Didipio stand at 50.1Mt grading 1.05gpt gold and 0.47% copper for a contained 1.69Moz and 240,000t copper.
The figures remain virtually unchanged compared to the December 2011 reserve statement.
Proven and probable reserves at the end of 2011 totalled 3.65Moz gold and 229,000t copper.
Moving on to measured and indicated resources, OceanaGold's total resource inventory sits at 6.73Moz of gold and 290,000t of copper, compared to 6.71Moz of gold and 291,000t of copper at December 2011.
OceanaGold said gold inventory net of mining depletion was marginally ahead, while copper inventory was stable year on year.
At Macraes, the company successfully replaced mining depletion with resources remaining in line with last year at 3.90Moz of gold.
OceanaGold managing director and chief executive Mick Wilkes said the company was able to achieve stable copper and gold inventories in 2012.
"This provides a solid mineral endowment as the company transforms itself in 2013 to a multinational gold producer," Wilkes said.
"We will continue to invest in exploration opportunities in New Zealand and we look forward to commencing a significant exploration program across our board portfolio of exploration prospects in the Philippines once the renewal of our exploration permits is received."
An update to the Blackwater project's resource in New Zealand is underway following the completion of the drill program in early 2013, and is tipped to be released to the market next month.
The company spent $US14.9 million ($A14.3 million) on exploration in 2012, mostly in New Zealand.
2013 is expected to be a transformational year for the company as it ramps up commissioning at Didipio and transitions into steady-state operations.
Shares in OceanaGold fell 3.3% to $A2.66 in morning trade.