The offshore safety regulator has halted drilling of the Barossa gas field 300km north of Darwin because vital safety equipment may not work in an emergency.
NOPSEMA ordered London-based Valaris to stop work on its MS-1 drilling rig on May 5 due to concerns about the blowout preventer (BOP) that is designed to quickly stop the flow of oil and gas from a well in an emergency.
The failure of a BOP to seal a well was central to the 2010 Deepwater Horizon disaster that killed 11 workers and caused a devastating oil spill in the Gulf of Mexico.
The regulator's direction, published on Monday, stated that "the BOP system is degraded and may not function as intended in an emergency scenario, such as a well blowout, resulting in a potential major accident event with serious or fatal health consequences to workers.
A set of hydraulic rams failed a pressure test conducted after the BOP had been installed underwater. The safety standard Valaris had told NOPSEMA it would follow requires two pairs of rams to be operable.
Prior to NOPSEMA issuing the legally enforceable stop work order, it had told Valaris it considered the state of the BOP to be unacceptable, and the company had not advised it whether it had taken any action.
Valaris must secure the well it is drilling as safely as possible and return the BOP to the surface to be fixed.
A Santos spokeswoman said the regulator ordered repairs to the BOP after a routine inspection.
"There was no safety incident and there is no threat to people, property or the environment," she said.
"Valaris is making the repair and expects to resume drilling later this week,
"The rig’s remaining work is to complete two of six wells, with the four completed wells already sufficient to achieve Barossa’s nameplate capacity."
Last week, Santos told investors that gas is scheduled to start flowing to Darwin in the September quarter.
I worked in oil & gas in commercial and engineering roles for 20 years. Since 2016, I have written for The West Australian, WAtoday and Boiling Cold, winning five WA Media Awards.
Peter Milne
