On 31 December 2024, there was an oil spill from Njord A. The Njord field is located in the Norwegian Sea, about 130 kilometres west of Kristiansund. Equinor is the operator.

The oil spill lasted for 2 hours and 20 minutes before it was stopped, and the total spill is estimated at about 75 m3 of oil.

Havtil made a decision on 10 March 2025 to conduct its own investigation of the incident.

The incident

The oil spill was in the form of oily water via the system for treating produced water.

Over time, the level control in the 1st stage separator at Njord A has been problematic. Instability in the water/oil boundary (here referred to as the water level) has been caused both by variations in flow rates into the separator and by weaknesses in the level control valve regulating the water exiting the separator. The instability has occasionally been handled by manually operating the level control valve.

Prior to the oil spill, the control room experienced such instability, putting the level control to manual, and therefore the level control valve in a fixed position, to handle this. The valve was left in this fixed position by mistake. This triggered the incident by causing the water level to fall and oil eventually joined with the water exiting through the separator’s water outlet, via the system for cleaning produced water and onward to discharge into the sea.

The discharge was detected by a person in the facility noticing an unusual odour and reporting this to the control room. The area operator then made a tour of the field, and reported that oil was observed on the water. The source of the spill was identified within approximately nine minutes. The produced water outlet from the separator was then closed and the discharge stopped. 

Direct and underlying causes

The proximate cause of the oil spill was that the level control valve on the water outlet from the 1st stage separator on Njord A was left in a locked open position after a manual intervention.

The cause of the incident was that the established barrier against a spill (the safety system that should close the emergency shut-off valve on the water outlet in the event of low water) did not function as intended. The level gauge showed an incorrect stably higher water level than the shutdown set point throughout the incident, and the water outlet was therefore not closed it as should have been.

There were no other technical barriers that could prevent the spill.

The investigation has uncovered several elements that have, or may have had, significance for the incident occurring and for the duration of the spill.

These include:

  • Need for manual intervention
  • Measurement concept and calibration of safety system and control system
  • Follow-up of safety function
  • Potential for capturing the incident
  • Transition from project to operation

Actual and potential consequences

The actual consequence of the incident was the spill of oil into the sea. The oil spill went on for 2 hours and 20 minutes before it was stopped, and the total spill is estimated at about 75 m3 of oil. The estimate is based on a change in the measured oil rate for export in the time before, during and after the incident.

The spill was detected by chance and, in other circumstances, it could have taken longer for it to be detected, which could have resulted in a larger spill.

The investigation has also identified potential consequences associated with overpressure in equipment downstream of the level control valve.

Non-conformities and improvement points

The investigation identified the following breaches of the regulations:

  • Level gauges in 1st stage separator were not calibrated correctly
  • Inadequate testing of safety systems
  • Deficiencies in process safety system
  • Single fault affecting both control system and safety system

During the investigation, we also observed the following factors that we have chosen to categorise as improvement points:

  • Lack of continuation and knowledge of assumptions from the project phase
  • Regulation of the processing plant

What happens now?

Havtil’s investigation has now been completed. We have asked Equinor to report to us on how the non-conformities will be addressed, and for their assessment of the improvement points observed.