East Coast Basin

Basin Summary

Although the East Coast region is geologically complex, it has long tantalised oil and gas explorers. Strong gas shows in the three offshore wells, as well as gas finds in the Wairoa area, have maintained exploration interest. The region has potential for large petroleum accumulations. All geologically-sited wells were drilled on anticlinal highs, most of which have proved to have little or no reservoir content. One possible reason may be that syn-tectonic deposition is commonly by turbid flows down the axes of synclines. Traps within synclines are yet to be tested, except perhaps by the small-scale 1880s oil production at Waingaromia.

• East Coast Basin Fact File [863 kB PDF]

• East Coast Basin Map [452 kB JPEG]

Key Facts
 

Location A region of about 120,000 sq km extending for 600 km onshore and offshore along the east coast of the North Island from East Cape to Marlborough in the South Island. Geology Basin formed at, and close to, the ancient Gondwana margin. Older basin-fill marine Early Cretaceous to Paleogene passive margin sequence. East Coast Allochthon extends part way across basin. Thick blanket of Neogene clastics. Now in a convergent margin fore-arc setting, with oblique subduction. Basin-fill may be up to 10 km thick.

Wells

More than 40 wells drilled onshore since 1955. Three offshore wells drilled Neogene strata.

Hydrocarbons

Over 300 oil and gas seeps known. All three offshore wells had significant gas kicks. Onshore, gas flow in Kauhauroa-1, near Wairoa. Small gas flow recorded in Te Hoe-1. Small volumes of oil produced from shallow wells and pits near surface seeps at Waingaromia and Rotokautuku.

Prospects

Numerous structural closures mapped onshore and offshore. Plays include inversion structures, fault-cored anticlines, stratigraphic pinch-outs, and shale-oil and  shale-gas.

Source rocks

Mid- and Late Cretaceous marine mudstones; Late Cretaceous to Paleocene Whangai Formation mudstone; Late Paleocene Waipawa Formation black shale.

Reservoir rocks

Mid- and Late Cretaceous transgressive marine sandstones and turbidite sandstones; fractured Whangai Formation shale and marl; Neogene turbidites; Neogene shallow water bioclastic limestones.

Port facilities

Port of Gisborne
www.eastland.co.nz

Port of Napier
www.portofnapier.co.nz

Wellington
www.centreport.co.nz

• New Zealand Infrastructure and Port Facilities [1.25 MB PDF]
   

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