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.
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. See the RNNP reports on trends in risk level in the petroleum activity for 2001-11.
According to operator Statoil’s own calculations (see document 43), 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.
The PSA resolved to initiate its own investigation of the leak. Go here for details.
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.
In addition, inadequate capacity in the fire water system and in the fire wall between the production and drilling areas was identified. These conclusions are presented in sections 7.1.1-7.1.9 of the investigation report.
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:
The deadline for compliance with this order is set at 1 March 2013.
Øyvind Midttun, Press contact
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