The Petroleum Safety Authority Norway (PSA) has revealed that during an investigation into the hydrocarbon leak on BP‘s Ula oil field in the North Sea, it identified serious breaches of the regulations and has ordered the company to conduct a safety review.

According to the safety authority, a hydrocarbon leak on the 12th September 2012 at the platform resulted in around 125 barrels (20 cubic metres) of oil and 1,600kg of gas being leaked.

The PSA investigation found that the leak was caused by the fracturing of bolts that were holding together a valve in a separator outlet.

During the leak, seepage in the valve exposed the bolts to produced water with a high content of chlorides and a temperature of about 120°C.

As a result, chloride stress corrosion cracked and weakened the bolts, until they finally fractured. PSA said that serious regulatory breaches were found at an early stage in the investigation, which prompted BP to adopt immediate physical measures on the installation.

"Seepage in the valve exposed the bolts to produced water with a high content of chlorides and a temperature of about 120°C."

On the basis of the findings from the investigation, the PSA has ordered the company to review its management system for the NCS.

BP has to evaluate whether the system is adequate to identify and manage risks, in addition to an assessment of why the system had failed to identify and deal with the nonconformities identified in the investigation of the leak on Ula.

The UK-based energy company will also have to assess whether measures planned and initiated after the fire on the Valhall platform in 2011, and other improvement activities, are relevant and adequate.

BP will have to complete the review by 1 September 2013, and will have to implement measures identified under the two items by 31 December 2013. The company stopped production at the field for 67 days following the leak incident, in which no people were injured.

In the investigation, PSA noted that the incident had the potential to become a major accident, which could have risked a number of lives and caused material damage.

Image: Ula lies in block 7/12 (PL019A) in the southern Norwegian section of the North Sea.