After an extensive seismic survey program, Origin has ranked the best drilling opportunities in licence PEP 38619 for a possible multi-well drilling program.

Early last year, the CGG Veritas vessel, Pacific Titan, shot about 1910km of 2D seismic over the Pantheon prospect and 432 square kilometres over the Nimitz prospect near the edge of the Taranaki and Northland basins for Origin and OMV, which hold equal stakes in the Origin-operated PEP 38618 and 38619 leases.

It also acquired a further 1200km of 2D seismic over the Akira prospect further offshore in PEP 38618.

Origin and OMV hold equal stakes in the PEP 38618 and 38619 leases, with Origin acting as operator.

Origin exploration manager Rob Willink told PetroleumNews.net the Nimitz survey had revealed some "excellent prospects" just north of Todd Energy's undeveloped Karewa gas field, about 50km off the Waikato coast.

Three prospects - Kokako, Korimako and Korimako South - were fault-dependent closures targeting potential Miocene and Eocene-aged reservoirs.

The fourth, Tarapunga, targeted a Pliocene-aged turbidite play similar to the Karewa discovery.

Willink said the seismic program had also uncovered two encouraging "giant leads", which he did not name, in the adjacent permit PEP 38618 located in deeper water, though these had higher reservoir and hydrocarbon charge risk.

The leads in PEP 38618 were targeting Eocene-aged turbidites in a large structure.

"Their areal closure is simply huge," Willink said.

He said the leads together covered about 500sq.km, with the potential to collectively contain several trillion cubic feet of gas or 100 million or more barrels of oil reserves.

Willink said Origin was looking to drill at least one of the prospects in the shallow water of PEP 38619 during 2009.

Water depths over the four prospects were about 100m and a large jack-up, such as the Ensco Rig 107, which is finishing drilling the three development wells for Origin and its partners at the Kupe gas field, could be used, Willink said.

Origin has also booked the Kan Tan IV semi-submersible rig for four wells.

These slots are nominally for the company's Bass Basin commitments but this rig could be used for a Northland well if the jack-up option is not pursued, Willink said.

Only three wells had been drilled in the Northland Basin.

The Kora-1 oil well, drilled by United States independent Arco during the early 1990s, indicated the presence of Waipawa black shale source rock.

A few years later, ConocoPhillips drilled the unsuccessful Wakanui-1 well a few years later, as well as Karewa-1 five years ago. ConocoPhillips then left New Zealand.

While Karewa-1 was not commercial, its results were interesting enough for Conoco's partner, Todd Energy, to retain a small part of the original permit.