OMV has been granted the last of the environmental consents it needs for a drilling programme off Taranaki this summer.
The company, which operates the Maui, Maari and Pohokura fields, has been granted a discharge consent for up to 11 wells it could potentially drill during the next five years in five permits it has interests in.
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The company plans to drill three wells off Taranaki this summer and is awaiting an additional consent required to drill one well in the Great South Basin off the south-east coast of the South Island.
Should the company receive that consent next month, the programme could get underway in December, a spokesman said.
Vienna-based OMV is New Zealand's biggest gas producer, having bought Shell's interests in the offshore Maui and Pohokura fields last year. It is planning to use the COSL Prospector, a modern, harsh-environment rig sitting idle since Tamarind Resources cut short a development drilling programme at the Tui field in September.
The consent granted for its Taranaki work, published by the Environmental Protection Authority yesterday, primarily covers harmful substances that will be discharged into the sea with the water-based muds used during drilling.
It also covers things like discharges from the rig's cooling systems, hydrocarbons from well tests and excess cement from well construction.
While some of the chemicals may prove lethal to plankton and small fish coming directly into contact with a concentrated discharge plume, the EPA said the overall the impacts of the programme on the Taranaki marine environment will be negligible.
"The effects of the discharges at a well site will dissipate to undetectable levels in an order of weeks to months."
OMV plans three wells in Taranaki and has previously described the programme as "pivotal" to its strategy for assuring long-term energy security for New Zealand.
Toutouwai-1 lies in a permit directly north of the Tui field which OMV manages on behalf of partners Mitsui and Sapura Energy.
Gladstone-1 lies further north, off the coast northwest of New Plymouth in a permit OMV shares with Malaysia-based Sapura.
OMV is also planning an in-fill well at the 40-year-old Maui field it is trying to extend the life of.
The firm's planned drilling in the Great South Basin – the first in 35 years – has been more controversial.
Tawhaki-1 would be drilled early next year about 146 kilometres south-east of Balclutha. The well lies in about 1,300 metres of water so is not especially deep by international or New Zealand standards and has about a one-in-six chance of success, OMV estimates.
In September, the EPA granted a consent for accidental discharges from the rig's deck drains during the programme. It resisted calls from opponents of the programme to broaden that public process to also include the applications it is now considering from OMV for marine consents and discharge consents for the Tawhaki drilling.