Taranaki Basin - NZ

The Taranaki Basin is a large complex basin that is located along the west coast of the North Island in New Zealand. The basin covers an area of about 115,000 km2 with most of the area being offshore. The eastern margin of the basin is defined by the large, north-south trending Taranaki Fault. To the northwest and northeast the basin joins the New Caledonia, Reinga and Northland basins although the boundaries are not well defined. 

History

The Taranaki Basin is New Zealand’s premier hydrocarbon basin and the only New Zealand Basin with commercial production to date. The basin has a long history of petroleum exploration dating back more than 100 years. Over two hundred exploration wells have been drilled and have resulted in forty discoveries, eleven of which are offshore. Discoveries in the offshore tend to be larger and include the giant Maui oil, gas and condensate field, large Kupe and Pohokura gas fields and the Tui and Maari oil fields. 

Geology

The Taranaki Basin was formed in the Late Cretaceous due to rifting associated with the breakup of Gondwana and the separation of New Zealand and Australia. This extension created a series of half-graben depocentres that were progressively filled with non-marine syn-rift strata followed by later marine transgression. The basin was part of a large passive margin setting during the Paleocene and Eocene that culminated in maximum marine transgression in the Oligocene with widespread limestone deposition. Tectonic compression and major uplift occurred in the Miocene and parts of the Taranaki Basin were inverted. The Pliocene to Recent has featured rapid progradation of the shelf and the development of thick clinoforms.

The main source rocks in the Taranaki Basin are Late Cretaceous to Paleocene-aged coals and coaly shales. These source rocks are buried unevenly across the basin and produce oil, gas and condensate depending on their depth of burial and thermal maturity. Reservoir and seal units are present throughout the Late Cretaceous to Miocene section and stacked pay intervals are common.