Assessment Of The MODU Rowan Gorilla I Capsize And Sinking

Abstract

The Rowan Gorilla I was a Mobile Offshore Drilling Unit (MODU) fabricated in Mississippi by the Marathon Le Tourneau Shipyard, and completed in 1983. The jack-up spent its first 5 years following completion off the east coast of Halifax, Nova Scotia involved in drilling activities for several clients. After remaining dormant for several months due to a decline in offshore activity in the fall of 1988 the decision was made to relocate the unit. On route to the North Sea, the unit, in tow by the tugboat Smit London, encountered unfavourable weather. The rig was down by the stern allowing waves to board the working deck. Green water reduced stability and compromised the water tight integrity of the deck. The following seas caused shock loading of the tow wire eventually leading to failure. The rig with stern facing the waves suffered severe impact loading for which it was not designed. Oscillating motions of the three 154 meter truss legs caused local hull fracturing resulting in ingress of water. The crew abandoned the rig after which it was observed to capsize and sink. The marine casualty can be attributed to a combination of factors which include the design of the rig, regulatory standards, personnel experience, and negligence. The sequence of events leading up to the loss was not anticipated by either party involved in the tow. It is evident that better planning and closer adherence to recommendations prior to departure may have resulted in a different outcome. The report to follow will outline the incident prologue and account, briefly discuss contributing factors, and outline the severity of loss, loss prevention and impact of the disaster. While conclusions have been included, enough detail is provided for the reader to execute their own assessment and draw relevant conclusions.