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The on and offshore Taranaki Basin is the only producing region in New Zealand. It contains a number of small- to medium-sized oil and gas fields. Clastic reservoirs occur throughout the Cretaceous to Cenozoic interval with discoveries in terrestrial, shallow marine, and deep marine formations.
The oldest producing intervals were deposited during Cretaceous rifting as the break-up of eastern Gondwanaland proceeded. Basin fill comprises Late Cretaceous to Late Oligocene sediments laid down in a transgressive phase.
The overlying Neogene is composed of thick, foreland deposits within a back arc and thrust belt setting. These were laid down in a regressive phase related to subduction at the Australian-Pacific Plate boundary.
All other basins in New Zealand have failed to yield commercial hydrocarbons although deep water regions have barely been drilled.
Oil and gas seeps, emanating from sediments of the Taranaki Basin, were first seen on Ngamotu Beach in New Plymouth by both Maori and early European settlers. The first well was then drilled in 1865 near Motorua where oil seeps had been recognised around a volcanic plug. The well, named Alpha, was hand-dug to 55m. It briefly produced oil at around 2 bbls per day from Pliocene sands.
Away from the Taranaki Basin oil seeps were reported from the East Coast Basin in the Poverty Bay District in 1866, from the Westland Basin at Kotuku in 1897, and in Chertsey Borehole-1, drilled in the Canterbury Basin in 1917.
The first commercial field was developed at Motorua and brought onstream in 1904. However, it was not until 1959 when a major gas discovery (Kapuni-1) was made by Shell BP & Todd Oil Services following an extensive seismic survey over the southern Taranaki Peninsula. It caused a surge in onshore activity in the area.
Motorua had been the only producing field until 1970 when Kapuni came onstream. The smaller McKee field was developed in 1980 followed by a series of modest-sized fields from 1988.
The Continental Shelf Act was passed in 1964 and drilling then began offshore on the Eastern Taranaki Mobile Belt and on the Western Platform. In 1969 Shell BP & Todd Oil Services discovered the Maui wet gas and oil field which was the largest in the country. Maui began producing in 1979.
Exploration then peaked in the mid 1980s but no further offshore fields were developed until 2006 during another peak in exploration activity.
Increased exploration activity ended in 2014 by which time a total of 62 discoveries had been made and there were 24 producing fields, all in the Taranaki Basin. The offshore fields, although much fewer in number, have produced substantially more oil and gas than the more numerous onshore fields. Oil and gas output, as well as activity, are now in decline.
In April 2018 the New Zealand Government announced a ban on new offshore permits and new onshore permits outside Taranaki as part of the Zero Carbon Bill. Consequently the 2018 Block Tender of onshore acreage was significantly reduced in area.
The investment potential of the country has thus been downgraded with some large companies exiting, although there remains a possibility that the policy could be reversed by a new government.
Oil and gas production and activity in New Zealand are forecast by Globalshift to continue the steady decline that began before 2014. Opportunities are dwindling, large companies are leaving, and environmental policies deter explorers from investing in the country.
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Oil and gas forecasts
NEW ZEALAND: SEDIMENTARY BASINS
Globalshift.co.uk (source: Te Ara Encyclopaedia of NZ)
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