Comprising two leaks on Statfjord B, where Equinor is the operator, the incident occurred in connection with running up after a turnaround. The leaks came from holes in two pipelines used for blowdown/pressure relief in process area M10T.
These leaks are estimated to have had initial rates of 0.52 and 0.57 kilograms per second respectively, with a total emission of about 285 kilograms of export gas.
Actual and potential consequences
The incident’s actual consequence was gas leaks with consequent shutdown, emergency response mobilisation and a delay of just under two days in restarting the facility.
No significant material damage was suffered except to the already degraded blowdown lines. No personnel were injured.
Under different circumstances, the gas leaks could have had greater consequences and lives might have been lost.
Direct and underlying causes
The direct cause of the leaks was external corrosion and consequent loss of integrity. Both pipes were probably corroded through before the incident occurred
Underlying causes are complex, with failure to carry out maintenance as a crucial factor. The investigation indicates a number of reasons why the necessary maintenance was not executed.
The investigation shows that this incident could have been avoided if Equinor had established a robust system for following up and maintaining control of the integrity of the blowdown lines.
The investigation has identified seven nonconformities, related to
- management of HSE
- knowledge of weaknesses in barriers and barrier elements
- marking of equipment
- maintenance programme
- maintenance criteria
- maintenance efficiency.
In addition, seven improvement points have been identified, related to
- assessing the HSE consequences of manning changes on Statfjord B
- assessing the HSE consequences of manning changes in the onshore organisation for Statfjord B
- ensuring competence (training backlogs)
- activating deluge
- plans for running up the facility after a turnaround
- evacuation measures
- ensuring appropriate behaviour.
The investigation has identified serious breaches of the regulations (see nonconformities 8.1.1, 8.1.4 and 8.1.5 in its report), and Equinor has now been given the following order.
Pursuant to section 69 of the framework regulations on administrative decisions, see sections 45 and 47 of the activities regulations on maintenance and maintenance programme respectively, and sections 58 and 59a of the technical and operational regulations on maintenance and maintenance programme respectively, see section 21 of the management regulations on follow-up, Equinor is ordered to do the following.
- Ensure maintenance of hydrocarbon pipes in carbon steel on Statfjord B so that they are able to perform their demanding functions in all phases of production life.
- Verify for all Equinor’s facilities and land plants that the maintenance programme for hydrocarbon pipes in carbon steel contains activities for monitoring performance and technical condition to ensure that failure modes which are under development or have arisen as a result of external corrosion are identified and corrected.
The deadline for meeting item 1 in the order is 1 June 2023. The deadline for meeting item 2 in the order is 31 December 2023. We must be notified when the order has been complied with in accordance with the specified deadlines.