Description of Incident
A snubbing crew rigged up on location. Set-up operations were completed for the wellhead stabiliser, snubbing jack, catwalk, pipe racks, pumping unit and primary accumulator. The crew was in the process of installing the snubbing unit equaliser line and the pumping unit flow line. The snubbing unit operator was installing the equaliser crossover into the production casing valve. The casing valve handle was in, what was assumed to be, a fully closed position. The downstream piping assembly was then depressurised and removed.
Upon removal of the downstream piping, the snubbing operator noticed an ice build-up inside the casing valve. The snubbing operator sprayed methanol to attempt removal of the blockage, but was not successful. The snubbing operator then used a steel chisel to break up the blockage. At this time, the snubbing supervisor entered the well head area near the affected production casing valve. When the ice plug within the casing valve was removed, a high pressure flow of wellbore gas and fluid was released.
The snubbing operator and crew evacuated the area and gathered at the safety meeting point. A head count revealed that the snubbing supervisor was not present and was still lying in the wellhead area near a crane. The crew retrieved the snubbing supervisor and controlled the well by fully closing the production casing valve.
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