Incident ID: 8346
Explosions or burns
Lifting, crane, rigging, deck operations
During a routine offshore well intervention for replacement of an Electrical Submersible Pump (ESP), at first an hydrocarbon release from the well occurred lasting approx. 3 mins at the workover rig floor, affecting rig floor, platform main deck and crane.
The activities were immediately stopped and instructions were given to secure the well and to start the oil clean-up from decks and structures. The situation was considered to be safe after the well was observed for a period of time in static conditions. The
water re-circulation inside the production string was started in order to remove hydrocarbon traces from the annulus and since the annular BOP could not guarantee the sealing due to the presence of the ESP electrical cable and control line, it was decided
to circulate with open well through the standpipe. During this activity a deflagration occurred under the rig floor, followed by an extended fire encompassing the workover rig and platform, resulting in 5 injured persons and a missing worker (crane operator).
Immediate shut-down of the platform was activated as well as the evacuation process. When the safety conditions allowed to re-board the installation, sadly the emergency team discovered on the crane platform that the missing worker had been fatally injured.
What Went Wrong:
- Oil presence on platform main deck due to hydrocarbon release during extraction of ESP followed by a well fill up. - Gas presence under derrick floor due to circulation with open BOP since ESP electrical cable and control line did not ensure BOP sealing.
- No continuous monitoring system for explosive mixtures in workover plant area other than platform fixed gas detector since ESP extraction was considered a low risk operation. - Presence of hydrocarbons (gas and oil) affecting rig floor, platform main deck
and crane was made worse by the presence of confined areas around the rig. - Too much confidence in workover activities conduction, considered routine activity, carried out in the same manner over the past.
- Install fixed gas detectors for explosive mixture in workover plant. - Ensure a continuous fill up, detailing this operation in the well program. - Ensure sealing of the annular BOP in presence of ESP electrical cable and control line, allowing the safety
fluid circulation through well control equipment. Formalise this action in an execution standard. - Ensure the availability of appropriate rope knife, allowing BOP complete sealing. - Ensure suitable and safe escape way from the crane cabin. - Ensure that,
in case of well servicing, risk assessment for SIMOP include plant layout associated with risk related to the presence of explosive mixture (not only H2S) and fire protection measures.