Petroleum potential of the deep water Taranaki Basin, New Zealand

Uruski, C. I., Institute of Geological & Nuclear Sciences, Lower Hutt, New Zealand, and Peter Baillie, TGS-Nopec Geophysical Company, Perth, Australia

Abstract

The New Zealand exclusive economic one (EEZ) contains at least six large deep water basins: the deep water Taranaki basin, the Raukumara basin, the Pegasus basin, the Head of the Bounty trough, the Great South basin and the Solander trough. Structural styles vary from rift basins through strike-slip dominated basins to major accretionary prisms. Source rocks encountered include coal measures, black marine shales and lacustrine facies. Sedimentary thicknesses, heat flow studies, and basin modeling, supported by production and numerous seeps in the shelf and onshore, suggest that these basins may be prolific hydrocarbon producers in the future. Recent developments suggest that the most promising of these basins is the deep water Taranaki basin, outboard of New Zealand’s only producing basin to date.

The petroleum histories of most of these basins began with the Late Cretaceous break-up of Gondwana and the formation of rift basins. In onshore New Zealand and on the continental shelf, many of the source rocks for the productive Taranaki basin were deposited at this time. The earliest sediments to be deposited were commonly fluvial, lacustrine, deltaic, and nearshore facies. and an increasing marine influence as the region foundered through the Paleogene.

The formation of the present plate boundary and the emergence of New Zealand in response to plate collision occurred during the Neogene. Many of the more spectacular structures in the New Zealand sedimentary basins formed during the Neogene. Meanwhile, the deep water basins away from the plate margin continued a quieter development. Some inversion occurred, but not to the extent of the nearshore and onshore regions. This relatively gentle structural evolution increases the likelihood of discovering large hydrocarbon fields in unbreached structural traps.