The company estimated between 3000 and 5000 litres of oil escaped. NOPSEMA is confirming the volume of oil lost and modelling the extent of its spread.

In March 2021, NOPSEMA ordered Jadestone to improve its management of corrosion after an inspection identified a string of issues including lack of action to identify problems and insufficient action when it did. The regulator again took action later in 2021 to stop the use of unsafe lifting equipment.

NOPSEMA said it would continue investigating the root cause of the leak.

The Montara spill comes just three months after about 25,000 litres of light oil called condensate leaked near Varanus Island off WA while Santos loaded a tanker.

In 2009, before Jadestone bought it, the Montara was the site of one of Australia’s biggest maritime environmental disasters. A wellhead blew out and oil flowed unhindered into the ocean for 10 weeks until the fifth attempt at sealing the well was successful.