Cyclone damage shuts Jadestone's Stag oil field off WA

Cyclone Narelle has shut down Jadestone Energy's Stag oil field, that now has a sinking mooring for oil tankers and damaged casings around wells drilled from the platform.

A number of industry sources told Boiling Cold that the cyclone left Stag, 60km north west of Dampier, with a CALM buoy that has lost buoyancy, and conductors that extend 70 m from the platform deck to the seabed, requiring repairs.

The UK-listed and Singapore-headquartered company may not have fully disclosed the cyclone's full impact to offshore regulator NOPSEMA.

A NOPSEMA spokeswoman said the company reported that the CALM buoy was damaged, but it was "following up with Jadestone regarding damage to other safety-critical equipment to understand the circumstances, including whether all relevant reporting obligations have been met," she said.

"As part of normal practice, NOPSEMA will investigate where the need arises, and where there is potential non-compliance, appropriate regulatory action will be taken."

**Oil is continuously loaded onto a tanker connected to the CALM buoy.** Image: Stag Environment Plan

The CALM buoy sits about 2km from the Stag platform, tethered to the seabed with six chains. It allows oil to continually flow from the platform to a waiting oil tanker.

The platform cannot store oil, so there can be no production until the CALM buoy is retrieved and then repaired or replaced.

The buoy has six watertight compartments and is designed to remain stable if one is flooded, according to the Stag environment plan, indicating that more than one compartment has been breached.

**Stag's CALM buoy can secure 150,000 tonne tankers**. Image: ONA Consultants

Jadestone told investors on March 30 that Stag was damaged after winds from Cyclone Narelle exceeded 200 km/hr, but released no details.

Jadestone started shutting down Stag on March 23, and pipelines were cleared of oil and workers moved to shore.

A spokeswoman told Boiling Cold that while its damage assessment was continuing, "there has been a partial loss of buoyancy in the CALM buoy and damage to some of the well conductors."

"We will provide an update in due course when further information is available."

The NOPSEMA spokeswoman said Cyclone Narelle was an extreme storm running down the coast of WA, impacting many offshore facilities.

"The industry activated cyclone preparedness plans immediately, and no injuries or major environmental incidents have been reported," she said.

Jadestone is claiming insurance for the damage to Stag and the cost of lost production and does not expect Cyclone Narelle will have a material financial impact.

An Australian oil portfolio with a big clean up bill

Jadestone produced 11,000 barrels of oil a day in Australia in 2024 from three projects that together impose a $US438 million ($614 million) clean-up liability on it.

The $277 million company's other Australian interests are the Montara oil field it owns and operates in the Timor Sea and a 33 per cent stake in some Carnarvon Basin oil fields operated by Woodside.

Jadestone, then called Mitra Energy, bought Stag off Santos in 2016 for $US10 million ($14 million).

Stag has been in the red for each of the five years to 2024, according to accounts filed with corporate regulator ASIC, with a total loss of $US63 million ($88 million).

During that time, annual daily production has fluctuated between a high of 2,672 barrels a day in 2023 to a low of 2,005 barrels a day in 2024. Stag contributes about five per cent of Jadestone's production.

Jadestone has recorded a $US127 million ($179 million) liability for decommissioning Stag and expects work to begin in 2036.

The accounts note that this estimate assumes some equipment can be left on the seabed based on past decisions by NOPSEMA despite "under Australian legislation, complete removal of offshore assets is mandated."

Montara produced 5262 barrels of oil a day in 2024 and made a loss of $US15 million ($21 million), according to the latest annual report filed with ASIC.

In September 2025 NOPSEMA directed Jadestone to urgently address corrosion on its 36-year-old Montara Venture oil vessel which "may pose significant safety and environmental risks."

Production from Montara was threatened by industrial action by workers for Jadestone subcontractor Legineering just as oil prices are at record highs. However, the union Offshore Alliance announced on Monday that its members had accepted a pay rise deal.

Jadestone has a provison of $US201 million ($282 million) for decommissioning Montara and expects work to start in 2031.

In 2022 Jadestone bought a one-sixth share of the Cossack, Wanaea, Lambert and Hermes (CWLH) oil fields fom BP and in early 2024 doubled its stake with a purchase from Japan Australia LNG, a Mitsui and Mitsibishi joint venture.

In 2024 Jadestone's share of production averaged 3711 barrels of oil a day and it made a $US36 million ($50 million) profit from CWLH.

It has provisioned $US110 million ($154 million) for its share of the cost of decommisioning from 2037 onwards. Like Stag, this estimate assumes NOPSEMA will allow some equipment to be left in the ocean.

Jadestone has contributed $US169 million ($237 million) to a trust fund to cover this future cost at CWLH.

The CWLH fields are not curently producing as the Okha production vessel sailed to Singapore for planned maintenance in January.

Jadestone Energy's Australian subsidiaries have entered into a deed poll with the the Australian Government to ensure ithe decommissioning costs will be paid when they arise.

The parent company must provide financial security to the Government when its future after tax tax flow is no longer 25 per cent higher than its decommissioning liability.