Buoyancy Spacing Implications for Fatigue Damage due to Vortex-Induced Vibrations on a Steel Lazy Wave Riser (SLWR)

摘要

As oil and gas exploration ventures into deeper waters, designing risers with sufficient extreme strength and fatigue lifernbecomes a challenging task. This task is even more difficult in regions with strong currents at great depths. Among thernhandful of riser concepts that can be used in such conditions, the Steel Lazy Wave Riser (SLWR) concept has shown greatrnpromise.rnThe SLWR concept does come with its own share of challenges. When deep ocean currents exist, obtaining sufficient fatiguernlife due to Vortex Induced Vibrations (VIV) becomes a major design challenge. A critical area of concern from VIV fatiguerndamage is the buoyancy section on the SLWR riser. Shell Oil Company performed some state-of-the-art experiments in 2011 tornstudy the effects of buoyancy spacing on VIV response. The experiments were performed at the Marintek Ocean Laboratory inrnNorway with a 38 m (～125 ft) long pipe what was 30 mm (1.18") in diameter. The buoyancy was simulated using 80 mm (3.15rn") diameter sections. This paper describes these experiments, discusses results and provides design insights on the effectivernsizing and placement of the buoyancy modules in SLWRs to minimize the fatigue damage caused by VIV.