New Zealand scientists have helped to confirm the potential for new oil reserves off Northland.

They say their findings, to be presented to an international oil conference next month, have great commercial and scientific significance.

The exploration and mapping of the giant Northland Basin was a bonus spinoff from a collaborative study of New Zealand's continental shelf by research teams from New Zealand's Institute of Geological and Nuclear Sciences and France's Geosciences Azur Institute.

They found a series of sedimentary basins just beyond the upper continental shelf directly north of Northland.

A member of the study team, geophysicist Dr Vaughn Stagpoole, said seismic mapping of the basin showed a similar geology to that of the Maui oilfields in Taranaki.

He will present those findings to the New Zealand Petroleum Conference in Christchurch next month.

"From our study it looks like there are all the elements required for petroleum generation and entrapment and in some cases it looks like there are quite large reserves," said Dr Stagpoole.

A United States company sank the first well in the Northland Basin last year but plugged and abandoned it when no hydrocarbons were found.

The Petroleum Exploration Association of New Zealand says the Northland Basin is regarded as virgin territory by international standards.

"The Maui oil and gas fields have been the main focus for a long time but they are in decline and there is no identified replacement for them," said spokesman Russell Plume.

While Dr Stagpoole expects there will be plenty of interest in the study findings at the conference, the cost of exploring in water up to 2km deep means that only a handful of the world's largest oil companies could consider drilling the area.

Study member Dr Rick Herzer said deep-water basins were coming into vogue as oil prices rose. They have nearly trebled in the past 12 months.

A further spinoff of the New Zealand-French research is what Dr Herzer describes as "the last great land grab" - the scramble by countries to define the outer edge of the continental shelf outside their 200 nautical mile limit. Under the Convention on the Law of the Sea New Zealand must make a submission on this to the UN by 2006. But that cannot be done until the underwater shelf has been clearly mapped.

Said Dr Herzer: "If you don't survey these areas, where there might be either overlap or a geological connection with neighbouring countries, we are at a disadvantage."