The incident occurred when the 13 ⅜" casing in the Q-21 well was to be cut in connection with the permanent plugging and abandonment of the well. The casing was cut at a depth of 510 meters, approximately 160 meters below the seabed. Shortly after the cut, large amounts of water and gas gushed uncontrollably onto the facility.

Equinor has estimated that approximately 930 kilograms of gas, consisting of a mix of methane, ethane and propane, was released.

There were 114 people on board the facility when the incident occurred. One person, who was in the shaker room, sustained minor injuries.

Major accident potential

Havtil considers the incident to be very serious, with the potential for a major accident. Under slightly different circumstances, the gas could have ignited, which could have resulted in serious injury or loss of life, as well as significant damage to the facility.

Direct cause

The direct cause of the incident was that gas from the reservoir, which had accumulated behind the 13 ⅜″ casing, was released when it was cut. The investigation shows that this was due to a failure in the well’s outer barrier.

Underlying causes

The incident had several underlying causes. These concerned a lack of barriers with respect to the reservoir, the use of technology and methods that were not qualified for the purpose, as well as weaknesses in planning, risk assessment and communication.

Faulty calibration led to misinterpretation of the log data, which contributed to the failure to detect the presence of gas. In practice, the cut was therefore carried out without functioning well control barriers.

Watch video

In the video above, we present the sequence of events and the main learning points from the investigation.

Non-conformities

The investigation identified 12 non-conformities. These concerned:

  • Inadequate design of well barriers
  • Inadequate quality assurance during the calibration of equipment for logging the 13 ⅜″ casing
  • Use of technology that was not qualified for well barrier assessments
  • Inadequate formulation of requirements in the well integrity manual
  • Missing well barriers during cutting operation
  • Noise level in the driller’s cabin during well control operation
  • Inadequate sharing of information about barriers and barrier impairments
  • Separation of HVAC 1 and HVAC 2 rooms
  • Failure to use differential pressure data
  • Lack of maintenance of differential pressure gauges
  • Inadequate formulation of requirements in the well control manual
  • Inadequate updating of technical documentation

One improvement point was also identified concerning the handling of hazard and accident situations.

Order

The scope and severity of the non-conformities have revealed a need to verify whether the elements of Equinor’s management system for planning and executing well workovers and permanent plugging operations are functioning as intended.

We have consequently issued Equinor with the following order:

Pursuant to the Framework Regulations, section 69 concerning administrative decisions, with reference to the Management Regulations, section 21 concerning follow-up, we order Equinor to:

  1. Review and identify deficiencies and weaknesses in Equinor’s requirements for risk management and follow-up in the planning and execution of workover and permanent plugging operations (DW200 – Workover and PP&A offshore), based on the incident of 23 September 2025.

The review shall include, but not be limited to,

    • control mechanisms such as risk analyses, verifications, and signing and escalation matrices
    • use of new technology/method

  2. Identify measures to address the deficiencies and weaknesses identified following the review in section 1. A time-delimited and binding schedule for implementing the measures shall be drawn up.

  3. An overview of the deficiencies and weaknesses identified by the review (section 1), the identified measures, and schedule for implementation (section 2) shall be submitted to Havtil.

The deadline for complying with the order is 17 September 2026. We are to be notified when the order has been carried out.

English version of the investigation report will be available shortly.