Associate Energy Minister Harry Duynhoven today announced preparation for a competitive bidding round had begun, with Crown Minerals joining forces with the Institute of Geological and Nuclear Sciences and UK-based seismic contractor Spectrum Energy & Information Technology to produce a substantial data package on the basin's prospectivity.

"The Northland Basin is located immediately north of the productive Taranaki Basin and initial interpretation, together with the results of Wakanui-1 (drilled by ConocoPhillips in 1999) show the Northland Basin is highly prospective," Duynhoven said.

Although planning had begun, permit boundaries had yet to be confirmed and relevant consultation done. The partnership between Crown Minerals and Spectrum would provide explorers with state-of-the-art reprocessed seismic data, Duynhoven added.

Spectrum will reprocess 9100km of existing seismic from offshore Northland Basin, while GNS prepares an interpretation and hydrocarbon potential report, based on the reprocessed seismic. Reprocessing should be complete by the end of January and the interpretation report will be completed before the anticipated bidding round.

Data to be reprocessed was a 1600km 1982 survey, originally acquired by WesternGeco and a 7500km 1995 survey acquired by ConocoPhillips and partners.

Duynhoven said test lines were already showing significant enhancements in data quality and imaging over the original processing. This was largely due to pre-stack time migration, advanced de-multiple techniques, more detailed velocity analyses and improved post-stack migration.

The Spectrum-GNS package will incorporate a revised understanding of the basin's near-shore potential by utilising recently released data obtained from the deepwater Wakanui-1 well, drilled off the continental shelf in 1999.

Initial interpretation from Wakanui-1 shows the Wakanui structure is not buried by marine Cretaceous rocks, as previously believed, and the presence of a Mid-Jurassic coal measure succession strongly suggests the presence of a new previously unsuspected petroleum system.

Seismic data suggests that the depocentre to the east of the Wakanui structure contains both Jurassic and Cretaceous source rocks and thermal modelling suggests that they are buried deep enough to be generating and expelling hydrocarbons.