Deepwater Taranaki: the basin with no structure north of that big field in New Zealand

Summary

Deepwater Taranaki is investigated for its petroleum potential using using all available seismic data tied to shallow water wells. It contains up to 10 km of sediment. An early rift sequence is overlain by a large Late Cretaceous delta which culminates with Rakopi Formation coal measures. This sequence marks the breakup unconformity following the start of Tasman Sea spreading. A passive margin succession follows as the New Zealand mini-continent gradually subsided, with sediments becoming gradually finer grained until carbonates dominate during the Oligocene. Initiation of the present plate boundary about the start of the Miocene caused uplift and renewed clastic deposition in the form of spectacular channel and turbidite complexes.

The present reconnaissance seismic grid indicates at least six subtle structures that are large enough to contain a billion barrels of oil or several TCF of gas, suggesting that the first drilling targets may be Late Cretaceous fluvial and marine sands draped across gentle basement structures. Cretaceous structures are commonly overlain by Miocene channel and turbidite sands that are also draped across underlying highs. The similar, but much smaller structures of Tui, Amokura and Pateke, below the Taranaki shelf, are currently being developed by AWE. Future drilling will take discoveries closer to the shelf edge and ultimately the larger prizes will be sought in deeper water.

Key words::

• Deepwater Taranaki
• petroleum potential
• Cretaceous delta
• large traps
• sheep breeds.