Christmas Tree damaged by wave

Print this pagePrint this page
Rating: 
No votes yet
Alert ID: 
03690
Description of Task: 

Normal production operations, Platform was under the Adverse Weather Policy so no individuals were exterior to the TR at the time.

At c.16:50 a wave struck the platform and caused gratings to lift in a lower module. The module is 23.2m above sea level and it is believed the wave was deflected upwards after striking one of the  legs.

One of the gratings struck a pressure transducer attached to the service valve on one of the Christmas Trees, causing a small hydrocarbon leak. This leak was reported to the CCR by a crew member working in an adjacent internal module, There were no F&G indication or annunciated alarms during this period. The CRO dispatched Operations to check this, who on reaching the area confirmed that the gratings were displaced and there was a leak. The platform went to manually activated GPA.

 

The Christmas Tree was isolated safely, by closing the manual master valve on the Christmas Tree and isolating the well by the HMV (Hydraulic Master Valve) and SSSV (Sub Sea Safety Valve). From the time of the first report to making the Slot safe and closing off the leak, between 3 and 5 minutes passed. At this time the Emergency Response Team arrived and barriered off the area with the displaced gratings. The plant was shut-down while the incident was fully understood and remained offline until the next day.

The grating sheared the instrument pressure transducer service line upstream of the Christmas Tree service valve. The instrument line is 8.5mm in diameter. The closed in pressure was 1800 psi. The  is a batch flow well with a 99.5% water-cut that is shut in at various periods to allow pressure to build up. The well was offline at the time of the incident. The calculation for oil released during this incident is between 4.9L and 8.18L based on duration.The gas released was calculated at release rate of 7.84kg per hour with a release volume of between 0.39 to 0.65kgs.

The following day the gratings were reinstated and production operations resumed, with Slot 1 remaining offline.
At the time of the incident the wind speed was 87 knots at 247 degrees. The wave height was in excess of 14m and clearly reached the production deck to displace the gratings in this area.

Lessons Identified: 

1.The investigation identified the need to review grating attachment, particularly around platform legs. so that gratings are suitable.

2.The adverse weather policy contained no pre-adverse weather checklist.

Recommendations: 

1.Review grating arrangements for areas with high potential for wave impact.

2.Update Adverse Weather Policy to include pre module check-sheet.

Specific Equipment: 

 Transducer attached to the service valve on well Christmas Tree.

Incident consequence: 
Hydrocarbon release
Activity: 
Production operations
Location: 
Fixed Installation
Cause of accident or incident: 
Uncontrolled release of a flammable gas or liquid