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Whanganui, King Country & Waikato Basins

Basin Summary

The Waikato and King Country basins offer little thermogenic oil and gas potential, though they do have a possible coal seam gas resource. The Whanganui Basin is perceived to be thermally immature and lacking in good source rocks.

Key facts

Location

Three basins which combined, cover about 40,000 sq km onshore and offshore the southwest coast of the North Island.

Geology

Relatively small, southward-propagating depocentres. Whanganui, the youngest, formed in the last 5 million years and contains about 5,000 m of latest Miocene to Recent basin-fill. In Waikato, Late Eocene alluvial to paralic coal measures are overlain by Eocene to Oligocene transgressive facies and Early Miocene turbidites.

Wells

Nineteen onshore wells have been drilled.

Hydrocarbons

No discoveries. Coal seam gas investigated and tested in Early Miocene (King Country) and Eocene (Waikato) coal measures. Biogenic gas known in Whanganui Basin onshore. Some higher hydrocarbons from onshore water bores.

Prospects

Plays include inversion structures, anticlines, stratigraphic pinch-outs, and drapes over pre-existing basement relief.

Source rocks

No effective conventional source rocks confirmed. Basal on-lap rocks may contain paralic facies. Eocene, Oligocene and Miocene coal measures present in King Country and Waikato regions. Quaternary peats may be sources of shallow biogenic gas.