What happened?
A wireline crew swabbed a sour well with a hydrogen sulphide (H2S) concentration of approximately 10 per cent. During the operation, the crew needed to remove the lubricator assembly to perform routine maintenance.
The crew closed both master valves on the wellhead, bled off pressure above the master valves and purged the system with nitrogen. Purge gas was introduced at the top of the lubricator assembly and from the wellhead wing valve to the well test separator and flare line.
Monitoring was conducted to verify the effectiveness of the purge. The lubricator assembly was disconnected from the wellhead by a worker wearing a supplied-air breathing apparatus (SABA). Following disconnection from the wellhead, the crew laid down the lubricator and performed maintenance, which took approximately one hour to complete.
The crew then commenced moving the lubricator back to the wellhead for reconnection. A wireline operator without SABA positioned the lubricator over the BOP when he noticed a strange taste and felt light-headed. He stepped back from the wellhead before losing consciousness and falling down the stairs on the wellhead platform. The injured worker quickly regained consciousness, was taken to the hospital for assessment, and released later that day. Upon investigation, wellhead master valves were confirmed to be functioning correctly
