In May and June 2024, three cases of decompression sickness occurred during surface-oriented diving on the Goliat field, where Vår Energi AS is the operator. The diving was carried out using a light diving craft (LDC) and with Nitrox as the breathing gas. The incidents occurred on two separate occasions:

  • 21 May 2024: One diver suffered decompression sickness after a dive to 19.5 meters for 75 minutes.
  • 2 June 2024: Two divers suffered decompression sickness after dives to over 21 metres with bottom times of 86 and 88 minutes.

All the divers were treated in a hyperbaric chamber. After the second incident, the diving operation was terminated and the project demobilised.

What is decompression sickness?

A dive consists of three phases: descent, bottom time at a given depth and ascent. The air pressure at the surface is one atmosphere and the pressure increases by one atmosphere for every ten metres of water depth. When the diver ascends to the surface, the ambient pressure decreases. The greater the depth under water and the longer the bottom time, the more the body’s tissues become saturated with gas.

At a controlled rate of ascent, the diver will eliminate some of the excess gas through gas exchange in the lungs. If the ascent is too rapid relative to the depth and bottom time, gas bubbles may form in the tissues and blood. “Decompression sickness” refers to various symptoms that can arise when the breathing gas taken up in the tissues and blood forms gas bubbles due to the reduction in ambient pressure as the diver ascends.

Decompression sickness is treated in a hyperbaric chamber by means of recompression and periodic breathing of oxygen in accordance with the Norwegian Diving and Treatment Tables (NDTT).

Decompression sickness may be reversible with rapid treatment. The health outcome for a diver following decompression sickness can range from no consequences at all to severe injury or long-term harm. Ultimately, severe decompression sickness can be fatal.

Actual and potential consequences

In the first incident, on 21 May 2024, one diver showed signs of cutaneous decompression sickness and possible neurological symptoms. The person was treated in the hyperbaric chamber and sent ashore for further medical monitoring.

In the second incident, on 2 June 2024, cutaneous decompression sickness was detected in two divers. No neurological symptoms were detected. Both were treated in the hyperbaric chamber. The companion divers received preventive treatment in the hyperbaric chamber.

The investigation considers that the potential of the first incident was eliminated. For the second incident, it is assessed that, under only slightly different circumstances, severe decompression sickness with permanent late effects could have occurred.

Direct and underlying causes

The investigation identifies several factors that, in combination, likely contributed to the occurrence of decompression sickness.

These include deficiencies in:

  • Management that takes uncertainty into account
  • Using the annexes to the NDTT
  • Organisation of the diving operation at Goliat
  • Vår Energi’s classification and follow-up of the first incident
  • Vår Energi’s assessment and qualification of the diving method
  • Vår Energi’s follow-up of the diving contractor

Non-conformities and improvement points

In the investigation, we identified two regulatory non-conformities. These concerned:

  • Inadequate follow-up
  • Inadequate decision-making criteria for surface-oriented diving

We also observed one factor that we have chosen to categorise as an improvement point. This concerned:

  • Inadequate specification of regulatory requirements

What happens now?

Havtil’s investigation has now been completed.

We have asked Vår Energi to report to us by 15 October 2025 on how the non-conformities will be addressed, and to give us their assessment of the improvement point observed.