Operational mistakes and a lack of maintenance led to near-fatal accidents at Norway's Troll field and at the Mongstad refinery, operator Statoil said on Friday.
A number of incidents at Statoil's offshore and onshore installations last year prompted several investigations by the company and authorities. In November, unions and Norway's safety watchdog warned that cost-cutting in the industry due to low oil prices could affect safety.
The latest two investigations by Statoil looked into an incident on Oct. 15 involving the loss of control on the Songa Endurance drilling rig of a well in the North Sea Troll field, and a hydrogen leak that occurred on Oct. 25 at the Mongstad oil refinery.
"This is among the most serious well-control incidents we've had," Statoil's head of technology, projects and drilling, Margareth Oevrum, told a news conference, in reference to the accident at Troll.
The well control incident led to a gas leak that pushed seawater more than 30 metres up the derrick, before the well was closed by the blowout preventer (BOP) about one minute later. A derrick supports the drilling apparatus on an oil rig.
A gas leak due to a break in a corroded pipe socket at the Mongstad refinery led to the facility's shutdown and evacuation.
The link between the incidents at the drilling rig and the refinery was a lack of understanding of the risks, not efficiency improvements or cost cutting, a Statoil spokesman said.
"Maintenance is decided by technical conditions, not economic considerations," he said.
Norway's biggest union of oil workers, Industri Energi, said cost-cutting was to be blamed, however, because it had resulted in laying off skilled workers and a fall in competence.
"This is not just about two isolated incidents, but it shows how cuts and reduction in competence and resources impacts health, environment and safety in all areas," the union's secretary, Haakon Aasen Bjerkeliveien, said in a statement.
Nobody was injured but Statoil said both accidents could have led to the loss of life if the safety equipment had failed or if the gas had been ignited.
"If the gas had caught fire, this incident could have caused fatalities," the head of Statoil's Marketing, Midstream & Processing unit Jens Oekland said, referring to the event at the Mongstad refinery.
Two people were in the vicinity when high-pressure hydrogen-rich gas was released.
Statoil said its investigation showed maintenance at Mongstad was wrongly prioritised due to lack of understanding of the risk and it would step up maintenance in the next two years.
"In this case, our risk management was inadequate. We made the wrong priorities," Oekland said.
Statoil also said it would not use the downhole valves, which were unintentionally opened during the well control accident at Troll, as barriers against the reservoir.
Norway's Labour Minister has appointed an independent commission to investigate the link between cost-cutting efforts and industry accidents.
In December, Statoil released reports on two other accidents, one of which injured five people, including two students on work placement, but the company said it had not found evidence linking those events to its cost cuts.