Economics of the Positioning of Drillships Using a Mooring and/or Dynamic Positioning System. Part 1. Mooring Analysis.

摘要

In the study a general applicable method has been derived to compare the operational costs of stationkeeping a drilling vessel by: a dynamic positioning system; and a dynamic positioning system in conjunction with a mooring system. The method has been applied to the 'Neddrill 2' drilling a well on a location nearby Tunesia in the Mediterranean. The use of the mooring system as a fully self-redundant system was not considered. Because of the presence of a dynamic positioning system, it was expected that nearly always the mooring system would be assisted by the dynamic positioning system to achieve the most cost-effective way of stationkeeping. Operational costs of stationkeeping drilling vessels in an environment of waves, wind and current are caused by the following factors: downtime due to the exceedance of the operational limits with respect to the motions of the vessel; power consumption of the dynamic positioning system; maintenance of the stationkeeping systems; and deployment costs of the mooring system.