At the time of the incident the platform was shut down (therefore the flare was unlit) and a nitrogen purge of annuli & flare system was taking place prior to breaking containment. The HP Flare system has no knock out drum and relies on an auto drain system to remove liquids. However, the auto drain was not functioning in auto mode, instead relying on periodic manual operation. The operations team & a vendor set up to nitrogen purge the Gas Lift header plus numerous gas lift flowlines. Well annulus fluids had accumulated in the flare system, but the auto drain was not manually operated prior to the purge commencing. As nitrogen was introduced to the purge envelope, the venturi effect was sufficient to pull fluid through the flare system with a coarse aerosol effect to sea.
- The issue of possible transfer of fluids to the HP Flare header had been considered prior to the venting task taking place and was considered to be a low risk.
- The importance of ensuring that the auto drain is fully functioning or any manual operation is tightly controlled to ensure no fluids are in the system.
- At re-start or during any venting it is important to check and establish whether it was gas or other fluids which are being bled
- Auto drain was unblocked, cleaned, inspected and reinstated for use.
- A PMR was raised to ensure that the correct maintenance regime is in place to ensure the continued correct operation of the auto drain.
- Operating procedures now require a visual check to ensure that the drains are free from fluids at various stages during venting operations (i.e. pre, during and post venting)