Regulator takes action against Woodside over riser turret mooring decommissioning

Australian offshore petroleum regulator NOPSEMA has taken action against the country’s energy major Woodside related to decommissioning of the Enfield field and Nganhurra FPSO.

Nganhurra FPSO
Topsides section of the RTM; Source: Woodside

Woodside operates the Enfield field within Production Licence Area WA-28-L located offshore Australia.

In 2018, the Nganhurra FPSO was utilised to flush, isolate, and preserve the riser turret mooring (RTM) and the subsea infrastructure, before the FPSO was disconnected and removed from the Enfield field.

The Nganhurra Operations Cessation Environment Plan (EP) was revised and resubmitted on 20 December 2019 to address alternatives for removal of the Riser Turret Mooring (RTM) from the field for onshore disposal.

Following further stakeholder consultation, Woodside elected to withdraw the EP and submit a new revision. The revised EP involves a more comprehensive evaluation of the impacts and risks associated with repurposing the RTM into an Integrated Artificial Reef (IAR), as well as further consideration of the practicability of onshore disposal.

NOPSEMA said on Friday it has accepted a revised Nganhurra Cessation of Operations Environment Plan by Woodside, for the decommissioning of the Nganhurra riser turret mooring from title area WA-28-L.

Production Licence Area WA-28-L - Woodside
Production Licence Area WA-28-L; Source: Woodside

Through accepting the environment plan, NOPSEMA has required Woodside to implement a range of protective measures to prevent and mitigate impacts to whale sharks, turtles, and seabirds.

In addition, NOPSEMA has initiated regulatory compliance action due to Woodside being unable to comply with an originally approved plan to remove the equipment for onshore disposal.

Due to the equipment’s poor condition and repair, this is no longer feasible without unacceptable risks to safety and the environment.

Woodside has been issued with enforcement action in the form of a General Direction requiring wells be plugged or closed off, and property no longer in use to be removed in a timely and proper manner.

The General Direction reinforces legal requirements regarding the removal of property associated with offshore petroleum activities and carries significant civil and criminal penalties for non-compliance.

Further, as Woodside is unable to decommission the riser turret mooring as originally approved, NOPSEMA is investigating possible breaches of the Offshore Petroleum and Greenhouse Gas Storage Act 2006. The investigation will examine possible breaches of the law relating to requirements to maintain property in good condition and repair, the regulator explained.

Decommissioning of the riser turret mooring can now be through removal from the title area for placement on the seabed as part of an integrated artificial reef.

Decommissioning in this way requires a permit under sea dumping legislation administered by the Department of Agriculture, Water and the Environment. This regulatory process is in addition to NOPSEMA’s assessment of Woodside’s environment plan.

Under the plan delivered by Woodside, the RTM removal is planned to be completed between March and April 2021 and is estimated to take 30 days.

If unable to meet this commencement window, the activities will be undertaken between December 2021 and March 2022.

Well intervention activities may start from 2021, depending on vessel/MODU availability and would be undertaken opportunistically. If undertaken, well intervention is estimated to take about 10-20 days per well.

If undertaken as a campaign, the cumulative duration is expected to be 18 months and may be performed over multiple campaigns.

NOPSEMA has issued a report addressing the key matters that arose through the assessment of the environment plan, including concerns around the degradation of the riser turret mooring.

In December 2020, NOPSEMA launched an industry-wide compliance plan to reinforce legal requirements regarding the removal of property associated with offshore petroleum activities.

Compliance actions include the issuance of Directions to some titleholders specific to decommissioning and end-of-life requirements.