The arrival of a specialist vessel at Port Taranaki this week marks the beginning of the final phase of decommissioning the abandoned Tui Oil Field.
The Tui field was deserted in 2019 after the financial collapse of Tamarind Taranaki, which left the Crown responsible for its safe decommissioning.
The Ministry of Business Innovation and Employment (MBIE) - which is overseeing the project - said the Helix Energy Solutions' Q7000 vessel would plug and formally abandon wells across the field.
The phase three work is expected to take about three months and the Q7000 will not be carrying out any new oil field activity during its time in New Zealand.
Helix Energy Solutions is an international provider of well intervention and abandonment services, and the Q7000 is the most modern vessel in its fleet.
Tui Project director Lloyd Williams welcomed its arrival, saying this phase had been in the planning for more than two years.
"The well plugging and abandonment is the most substantive part of the Tui decommissioning project," Williams said.
"It involves re-entering wells on the seafloor and then positioning cement plugs about 3000m below the surface.
"In addition, we will remove any equipment on the wells from the seafloor."
The project was providing opportunities for New Zealand specialists and local suppliers, Williams said.
"Over 50 percent of the offshore crew of around 100 will be New Zealanders or Australians, and more than 20 local businesses are contracted to support the project."
MBIE has partnered with Te Kāhui o Taranaki (Taranaki Iwi) for the Tui decommissioning.
Tumuwhakarito (chief executive) Wharehoka Wano said the arrival of the Helix marked an important next step in the project.
"It's vitally important Taranaki Iwi and the hapū of Ngāti Kahumate, Ngāti Tara, Ngāti Haupoto and Ngāti Tuhekerangi continue to work closely with MBIE on this project," Wano said.
"As kaitiaki, we ensure our taiao and important cultural resources are protected and enhanced for the next generations."
Following this phase of work, the Tui Project will focus on removing the four mid-water arches, which is a residual task from the previous phase.
In May, MBIE signed an agreement with Sapura Projects, an Australian-based supplier of subsea services, for this work to be carried out in the coming summer period.
Removing the mid-water arches will be the final step in the Tui Decommissioning Project.
Port Taranaki commercial head Ross Dingle said the Q7000, which was in transit from Perth, would come to port under its own steam and be provided with a pilot and tug support to bring it into berth.
"Dozens of workers and project staff will be joining the vessel in New Plymouth, so it works well for the vessel to come into port for the crew transfer and to load supplies before heading to the site."
Energy consultancy Elemental Group is providing project management assistance for Helix Energy Solutions in New Zealand.
Director Nick Jackson said as well as providing logistics support and assisting with health and safety and environmental compliance, the company was assisting with procurement, and managing the New Zealand companies needed for the project work.
"All up, there will be a team of more than 100 on the Q7000, over half being Kiwis and Aussies in operations roles working alongside the Helix crew, as well as several specialist roles, such as wireline and cementing," Jackson said.
"We're excited to be a part of the project. I worked on some of the original Tui exploration wells, so it's nice to be involved in restoring the mauri of the area."