PSA: Heimdal Leak among the Most Serious Gas Emissions on NCS

The Petroleum Safety Authority Norway (PSA) has notified Statoil of an order after its investigation of a hydrocarbon leak on Heimdal platform on 26 May 2012. The report identifies serious non-conformities from the regulations which are significant for safety.

The hydrocarbon leak occurred in connection with the testing of two emergency shutdown valves (ESDVs) on Heimdal’s HMP1 production, drilling and quarters platform.

To prepare for the test, a pipeline was to be depressurised to the flare. This contained a ball valve with a 16-bar pressure class as the final barrier against the flare. Because it was closed, the valve experienced a pressure of 129 bar.

Gas leak

The pressure caused the seal in the valve flange to fail, resulting in a gas leak estimated at 3 500 kilograms. The initial leak rate was 16.9 kilograms per second (k/s). Gas was detected across a large area of the installation.

This leak ranks among the most serious gas emissions on the Norwegian continental shelf (NCS) for several years.

According to operator Statoil’s own calculations, the leak on Heimdal caused the emission of 3 500 kg of gas over a period of 252 seconds with an initial rate of 16.9 kg/s. The total gas volume in the piping segment was 7 000 kg.

Non-conformities

This investigation has identified serious non-conformities from the regulations which are significant for safety.

These non-conformities show that important improvement measures identified and implemented by Statoil after earlier incidents, such as the hydrocarbon leak on Gullfaks B of 4 December 2010, have not had the expected effect on Heimdal.

Non-conformities have been identified in relation to the design solution, identification of the relevant design solution, and descriptions of how the work should be done.

They also relate to Statoil’s document management, risk assessment during planning, experience transfer and learning from previous incidents, expertise and risk understanding.

Potential

In addition, inadequate capacity in the fire water system and in the fire wall between the production and drilling areas was identified.

A number of the non-conformities also involve weaknesses in the work of management in following up that the activity was being conducted in an acceptable manner.

The incident had a substantial potential for harm in the event of ignition or in marginally changed circumstances. The PSA concludes that it had a clear potential to become a major accident.

On that basis, the PSA has given Statoil notification of the following order:

Pursuant to section 69 of the framework regulations on administrative decisions, see section 6 of the management regulations on the management of health, safety and the environment and section 21 on follow-up, Statoil is ordered to:

• identify the reasons why the improvement measures adopted by Statoil have not had the necessary effect on Heimdal
• ensure that the improvement measures mentioned above have the necessary effect on Heimdal, and present a plan for the work required to achieve this
• confirm that similar conditions indicating a lack of effect from the above-mentioned measures do not exist on other Statoil installations.
• The deadline for compliance with this order is set at 1 March 2013.

Heimdal

The Heimdal Gas Center, on Production License (PL) 036, is a hub for the processing and distribution of gas. It consists of an integrated steel platform, and a riser platform.

Gas from Heimdal is processed together with gas from the Huldra and Vale fields.  In addition, Heimdal receives gas from the Oseberg Field Center through the Oseberg Gas Transport system (OGT).  Periodically, reverse gas flow from the Statpipe pipeline goes to Heimdal and on to Vesterled.

Heimdal is also equipped to export gas as pressure support to produce oil on the Grane field, after it started operating on October 1, 2003.

The total maximum rate of processed gas on Heimdal is comparable to some 15-20 percent of Norway’s total gas export.

Related:

Statoil Submits Heimdal Gas Leak Investigation Report to PSA Norway

Statoil: Heimdal Gas Leak Under Investigation (Norway)

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Press Release, December 20, 2012