No abstract

The Horn Mountain Production Spar was installed in 5,400 feet of water in June 2002. This was the deepest floating production unit at that time. A comprehensive instrumentation program was initiated to measure spar and riser responses (Edwards et al, DOT 2003). The present paper discusses the results of these measurements and comparison with analytical predictions of spar behavior during two selected events, hurricane Isidore in September 2002 and a summer storm in August 2003. Particular attention has been placed on the slowly varying surge and pitch motions and the importance of coupling with risers and mooring on hull motions. Our conclusion is that uncoupled analytical models for spar behavior predict accurately the wave frequency responses, however riser coupling has an influence on the slowly varying responses. This conclusion is consistent with earlier measurements of classic spar behavior (Gupta et al, OTC 2000, Prislin et al, OTC 1999).

No abstract

The Horn Mountain Production Spar was installed in 5,400 feet of water in June 2002. This was the deepest floating production unit at that time. A comprehensive instrumentation program was initiated to measure spar and riser responses (Edwards et al, DOT 2003), while motion comparisons were presented on previous publication (Halkyard et al, OMAE 2004). The present paper discusses the results of these measurements and compares with analytical predictions of spar mooring tension during hurricane Isidore in September 2002. Particular attention has been placed on the importance of Coulomb friction between wire chain and the fairlead bearing to the dynamic tension of mooring lines. Mooring tensions were measured at chain jack location (inboard tension), while analytical models computed those tensions at the fairlead location (outboard tension). Our conclusion is that there is excellent agreement between field measurements and computed tensions at the chain jacks when fairlead friction is included, and when the vessel motions are accurately predicted. Ignoring fairlead friction results in a slightly conservative estimate for the tension at the chain jack. This has been the standard practice in all spar designs to date.