Alert 22-05 Semi-submersible Mobile Offshore Drilling Unit (MODU) Unlatched From Well in Progress

WHAT HAPPENED:

A semi-submersible Mobile Offshore Drilling Unit (MODU) was unlatched from the well in progress and located at a survival location during a storm. A dual wire mooring line failure occurred to simultaneously positioned lines. The failure of the wires allowed the free azimuth of the associated fairleads which punctured the hull, and over the ensuing period, the fairleads clashed, causing significant damage to both fairleads. The primary failure mechanism of the wires was identified as high load – low cycle bending fatigue…