Authors: Márcio De Abreu Grove; Ricardo Portella; C. Levi
Addresses: Projemar Engineering Co., Rio de Janeiro Brazil. ' Projemar Engineering Co., Rio de Janeiro Brazil. ' Laboratório de Tecnologia Oceânica LabOceano, COPPE UFRJ, Rio de Janeiro Brazil
Abstract: An innovative concept of station-keeping system to be used in Floating, Production, Storage and Offloading (FPSO) production units located in deep waters is described. The new concept combines the conventional catenary mooring lines (namely, spread mooring), in a special configuration known as 'Differential Complacency Anchoring System DICAS', with thrusters controlled by dynamic positioning system. The chief idea behind such a hybrid system is to design the conventional mooring system just enough to support the usually mild operational environmental loads and consider thruster assistance to cope with the more severe survival conditions. Such a combination may allow for reducing the total number and/or size of the mooring lines to be employed. In addition, the occasional use of the thrusters reduces their working time, having a positive impact on their operational costs and reliability. As one may expect, acquisition, installation and maintenance costs of the conventional mooring system are largely dependent on water depth. On the other hand, dynamic positioning costs are nearly constant with respect to water depth. Therefore, it would be possible for a given environmental condition to find the water depth above what it would become more economic to install the hybrid system in the FPSO. A further benefit obtained from the hybrid system is due to the horizontal complacency of the DICAS mooring line arrangement. The thruster lets interventions, applied to change FPSO heading, to reduce, within certain limits, the hull roll motions when energetic swells come from aside (beam seas). As a result, the FPSO working time and operational safety index may be accordingly increased.
Keywords: deep water production units; FPSO vessels; ship hydrodynamics; offshore oil production; station-keeping systems; spread mooring; differential complacency anchoring; dynamic positioning.
International Journal of Computer Applications in Technology, 2012 Vol.43 No.3, pp.234 - 247
Published online: 03 Apr 2012 *Full-text access for editors Full-text access for subscribers Purchase this article Comment on this article