The decommissioning of the abandoned Tui oil field off the coast of Taranaki has hit a bump in the road.
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 was overseeing the project - said Helix Energy Solutions' Q7000 Heavy Well Intervention vessel was leaving New Zealand waters without completing the full scope of phase three work expected.
Q7000 arrived in New Zealand in late May and was expected to take three months to plug and formally abandon wells across the field.
The work included re-entering four wells and then positioning cement plugs about 3000 metres below the seabed surface. This was the most substantive part of the decommissioning.
Tui Project spokesperson Melanie Sole said the work had taken longer than expected, but could not say whether this had affected the costs of the phase three decommissioning work at Tui because they had not yet been been determined.
Neither the Tui Project or MBIE would be liable for any late penalties occurred by Helix for arriving late at its next client, she said.
The majority Helix's phase three work had been completed, including:
- Plugging of the four ex-production wells
- Retrieval of five Christmas (Xmas) trees
- Severance and recovery of six out of eight wellheads
Work remained to be done on two wellheads which were still exposed on the seafloor.
"The two remaining wellheads protrude above the seabed. The Tui Project's overarching approach to decommissioning is to leave a 'clear seabed' through the recovery of all subsea equipment and removal of all wellheads to below the seabed surface."
Sole said that work would be picked up by another contractor already expected on site early next year.
"The remaining two wellheads will now be transferred to Sapura Energy Australia to complete, in addition to removing the four mid-water arches. This campaign is scheduled to begin in February 2024. Sapura is well equipped to undertake the work.
"Sapura was contracted in May this year to remove the mid-water arches in early 2024 (residual work from Phase 2), and to undertake any wellhead severance and recovery operations remaining from phase three."
This would be the final step in the tui decommissioning project.
MBIE has partnered with Te Kāhui o Taranaki (Taranaki Iwi) for decommissioning.
Sole said the ministry had been in regular contact with Te Kāhui o Taranaki which was aware the outstanding phase three work had been transferred to Sapura Energy.
The final work was schedule to be completed during summer.