Griffon Hoverwork Ltd (GHL) was commissioned by Shell in 2009 to complete concept designs of fit for purpose hovercraft capable of conducting year round activities, from shore to 15 nautical miles offshore in the Beaufort Sea and further offshore in the Chukchi Sea. This required that the designs have the capability to operate in extreme cold conditions (-40°C) and have the ability to cross ice ridges of significant height.
The operation calls for three distinct types of hovercraft:
A Routine Re-supply craft capable of carrying 30 tonne of cargo or passenger modules.
A Hoverbarge capable of carrying a payload of 150 tonne.
An Escape, Evacuation, Rescue (EER) craft for evacuating the rig in case of fire or other emergencies, to be positioned on the rig.
Previous work for Shell by D.F. Dickins Associates, had shown that the hovercraft may offer logistics options and a secondary solution to the problem of emergency evacuation of installations off the North Slope of Alaska.
As starting points, Shell provided outline concepts for two logistics craft. For the EER role, GHL have two examples of commercially available hovercraft designs that have been tried and tested in service, namely the Griffon 8100 and the BHT150. It has been reasoned that the 8100TD cannot be designed with any greater cushion height than 2.5m and the BHT150 no greater than 3.0m. Part of the requirement was to take as much research information as possible from cold weather hovercraft operations and then, using a many proven components as practical, develop the concepts. A ridge crossing formula was developed to model the capabilities of the craft and determine the ridge approach speed. From the outset, it was relised that existing craft would require extensive modifications, particularly to the skirt in order to increase the cushion clearance for operations over rough ice and potentially high sea states. This in turn required the craft to be increased in width to maintain stable operation.
The paper will show how the solutions were developed, how the key obstacles were overcome, and will explain how further research is being undertaken.
Significance of Subject Matter.
This paper describes how appropriately designed hovercraft can provide important solutions for some of the logistics and emergency evacuation problems that are foreseen for the oil industry operating offshore in the Arctic.