The Petroleum Safety Authority Norway (PSA) completed its investigation on the fire in the mud laboratory on West Phoenix of 5 November 2018. The report identified several breaches of the regulations. This rig is operated by Seadrill Management (Seadrill), and was drilling well 6406/2-9 S in Norwegian Sea with Equinor as the operator, when the incident took place.
The incident
The incident happened in connection with testing drilling fluid (mud) in a retort in the lab.
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A retort is an electrical apparatus which measures and monitors the quantities of water, oil and solids in drilling fluid. While drilling is being conducted, the retort is usually used several times a day to check the density and content of solids and water in the fluid.
The retort was being used when the fire started. Nobody was in the lab, but the smoke alarm was activated and personnel could confirm the presence of flames in the room. A general alarm was also activated, and all personnel mustered. There were 117 people on board at the time.
The fire team arrived on the scene and used powder and then water. The entry into the room was prevented by the high temperature, and the fire was fought through the doorway. The fire was confirmed as extinguished at 15.10.
The incident caused material damage, as well as a five-day halt to drilling. No people were injured.
As PSA notes, the mud lab was not regarded as an area with a high probability for a fire, and the walls met fire class A0. If the fire was not quickly extinguished, it would probably have spread because flammable materials were stored and used in the room.
In addition, fire damage to cables passing through the mud lab and/or the fire spreading to the near cement operator station would have led to a longer halt to drilling and significantly greater material damage. Spreading of the fire could also have distributed smoke to large areas of the facility.
Probable cause
Investigations by the National Criminal Investigation Service found that the fire was probably caused by serial arcing in the extension cord used. This arcing caused a high temperature and ignited flammable material which was nearby. The arcing was probably caused due to an insulation failure after a mechanical damage.
Moreover, chemicals used for mud testing were stored in the fume cabinet. Design drawings show that this cabinet should be made of stainless steel, but the fire damage indicates that it was clad internally with flammable sheets. The chemicals and the flammable sheets inside the cabinet led to the quick escalation of the fire.
Non-conformities
The PSA’s investigation identified a few breaches of the regulations and conditions with a potential for improvement. Three non-conformities have also been registered, regarding the following conditions.
- Use of extension cords with a 16A overcurrent protected device;
- Retort;
- Fume cabinet design.
Furthermore, four improvement points have been identified, regarding the following:
- Portable third-party equipment taken on board;
- Checking of extension cords;
- Storage of flammable materials in the mud laboratory;
- Maintenance of retorts.
What is more, information from the police on the findings of the forensic examination showed that a break in the extension cord was the probable cause of the fire. This was communicated to the companies, so that they could take the necessary measures.
Now, PSA’s investigation has been completed, and Seadrill has been requested to explain how it will deal with the non-conformities. The deadline for a response has been set until 29 March 2019.
See more information in the PDF herebelow
