With probe into gas leaks on North Sea platform done, Equinor gets regulatory order

Norwegian offshore safety regulator has finished investigating gas leaks on an Equinor-operated platform in the North Sea, located on one of the oldest producing fields on the Norwegian continental shelf (NCS), and followed it up with an order to the operator.

The Petroleum Safety Authority Norway (PSA) reported on Thursday, 23 February 2023, that it had issued an order to Equinor, following an investigation of gas leaks on the Statfjord B platform on 23 May 2022. According to the PSA’s report, breaches of the regulations have been identified, and Equinor has now been given an order.

The offshore safety watchdog explains that the incident, comprising two leaks on Statfjord B where Equinor is the operator, occurred in connection with running up after a turnaround and the leaks came from holes in two pipelines used for blowdown/pressure relief in the 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.

Based on the Norwegian regulator’s statement, the incident’s actual consequence was gas leaks with a consequent shutdown, emergency response mobilisation and a delay of just under two days in restarting the facility while no significant material damage was suffered except to the already degraded blowdown lines. The PSA confirmed that no personnel were injured. However, the gas leaks could have had greater consequences under different circumstances and lives might have been lost.

The offshore safety watchdog’s investigation outlined that the direct cause of the leaks was external corrosion and consequent loss of integrity, as both pipes were probably corroded through before the incident occurred. The PSA says that the underlying causes are complex, “with failure to carry out maintenance as a crucial factor.”

The regulator’s investigation indicates a number of reasons why the necessary maintenance was not executed and shows the 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.”

While conducting its investigation, the PSA identified several breaches of the regulations. The seven nonconformities that the regulator found include management of HSE, knowledge of weaknesses in barriers and barrier elements, marking of equipment, maintenance, maintenance programme, maintenance criteria, and maintenance efficiency.

In addition, the Norwegian regulator identified seven improvement points 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, and ensuring appropriate behaviour.

On that basis, Equinor has been ordered to ensure the 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.

Additionally, Equinor has been ordered to verify that the maintenance programme for hydrocarbon pipes in carbon steel for its facilities and land plants 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 Petroleum Safety Authority confirmed that the deadline for compliance with the first item is 1 June 2023, while the deadline for meeting the second one is 31 December 2023.

“We must be notified when the order has been complied with in accordance with the specified deadlines,” concluded the PSA.

The Statfjord B platform stands on the Equinor-operated Statfjord field, which is located in the Tampen area in the northern part of the North Sea on the border between the Norwegian and British sectors. The Norwegian share of the field is 85.47 per cent and the water depth at the site is 150 metres. 

According to Equinor, Statfjord is one of the oldest producing fields on the Norwegian continental shelf and the largest oil discovery in the North Sea. Discovered in 1974, the Statfjord field has been developed with three fully integrated production platforms: Statfjord A, Statfjord B, and Statfjord C.

Statfjord B in the southern part of the field came into production in 1982 and the Norwegian share of the field lies in blocks 33/9 and 33/12 in production licence 037, while the British part is in UK block 211/25 in licences 104 and 293.