He said that Taranaki, situated close to tectonic plates, had so far produced 500,000 barrels of crude and condensate and 1.7 billion barrels of oil equivalent (boe) of gas from an area of about 100,000 square kilometres.

"But the potential for big oil is in the basins away from the tectonic plates, and that often means deep water," Uruski said.

New Zealand's deepwater basins, which cover about 1 million square kilometres have the potential to produce at least 17 billion boe.

Uruski said GNS and Crown Minerals had so far mapped or interpreted existing mapping of many of the deepwater basins surrounding New Zealand.

This work has identified many anticlines and stratigraphic structures.

The Great South Basin was perhaps the deepwater basin with the greatest potential, Uruski said. GNS and Crown Minerals' seismic had been a factor in attracting three joint ventures - headed by ExxonMobil, OMV and Greymouth Petroleum - that are planning to spend up to $NZ1.2 billion in the area over the next five years.

Meanwhile, GNS and Denver-based Global Resource Holdings have already identified several structures in the Deepwater Taranaki Basin that could each contain one billion barrels of more of oil, if filled to spill point, Uruski said.

Global is presently trying to farm-out some of the 100% interest it holds in its Deepwater Taranaki block.

Further north, Origin Energy and OMV are planning an exploration program over offshore Northland acreage where GNS has also reprocessed seismic.

And the Raukumara Sub-basin, north of the North Island's East Cape, was also full of potential, with at least a dozen leads identified that could hold one billion barrels or more of oil, according to Uruski.

Raukumara was relatively undeformed, compared with the East Coast basin to the south, he said.

PTTEP president Maroot Mrigadat agreed with Uruski's assessment that New Zealand, particulary the Great South basin, has similarities with the North Sea.

Mrigadat told the conference on Monday that his company's first foray into New Zealand - as a partner in Great South Basin exploration - was a high-risk, high-reward position that was balanced by New Zealand being the "perfect low-risk" country, with its strong fiscal and regulatory regimes.

Last year the Thai company won three Great South Basin blocks (36%) in conjunction with Austrian giant and operator OMV (36%) and Mitsui (28%).