Gas supplies are set to be reduced because of problems at several of the country's biggest fields.
The Pohokura Platform off the coast of North Taranaki. Photo: Supplied
Contact Energy has been told its allocation of gas from the offshore Maui and Pohokura fields will be cut by 3.7 petajoules (PJ) to 10.6 PJ for next year, down about a quarter on its supply for 2020.
The primary issue appears to be with the Pohokura field where there has been an unexpected and unexplained fall in production.
The field's operator, Austrian-owned OMV, has been investigating why Pohokura's output has fallen as much as 15 percent after maintenance work on several wells earlier in the year.
In September, the company brought into operation a large compressor to increase production from the field which supplies 40 percent of the country's natural gas.
OMV said it was still looking into the fall in production from offshore wells, but expected tests might provide some causes and possible remedies.
"The production outlook for 2021 remains uncertain and it is too early to indicate the impact of the ongoing well interventions or any future work that may be undertaken in 2021," the company said in a posting on a gas industry website.
OMV said it expected production from Pohokura for next year to be around 39 PJ, which compared with 67.7 PJ produced in the 2019 calendar year.
Unexpected outages of the field in 2019, which reduced gas supplies, were a factor in a major spike in wholesale electricity prices which affected thousands of consumers.
Other fields
Production from the Kupe offshore field is also be reduced because of problems with equipment.
Australian firm Beach Energy which operates the Kupe field, the country's third biggest field, said the field's offshore platform has a problem which will also reduce gas production.
The Kupe partners - Beach, Genesis Energy, and NZ Oil and Gas - are looking at further drilling and exploration of the field. That has triggered a review by Genesis about whether it should keep its 46 percent stake.
Meanwhile, OMV has said it expects next year's production from the Maui field to be about the same as 2019 at about 22 PJ.
The Petroleum Exploration and Production Association of New Zealand (PEPANZ), the oil and gas sector's lobby group, said natural gas supplies are at risk and called for greater flexibility in gas permits.
"Despite having our own natural gas here in the ground, we could end up reliant on imported LNG from Australia if we aren't careful," PEPANZ chief executive John Carnegie said.
The group's post-election briefing paper included a call for a look at extensions of both geographic areas and time limits in exploration permits, as the country faced a 60 percent fall in gas production over the next decade.