THE WOODLANDS, Texas – INTECSEA’s Worley Parsons Group is featuring its FHSB Semi design at the Deep Offshore Technology conference being held at The Woodlands Waterway Marriott Hotel & Convention Center. The company says the new design enables semisubmersibles to be suitable for dry tree applications in harsh environments.
INTECSEA says that top tensioned risers (TTRs) have their advantages in allowing direct vertical access to production wells. However, due to tensioner stroke limitation, the use of TTRs requires a floating system that provides minimal heave response. Both spars and tension leg platforms (TLPs) have been recognized by their favorable response and therefore their suitability to support TTRs.
But in water depths beyond about 1,500 m (5,000 ft), the company says that TLP tendon design becomes increasingly challenging, leaving spars as the only feasible solution in ultra-deepwater. However, the single column configuration of spars can support limited deck area, and poses restrictions on the maximum payload. Spars also require hull upending and topside integration through heavy lifts offshore. These operations bring their own cost and risk disadvantages.
Conventional semisubmersibles provide significantly larger deck area, are less sensitive to payload and do not require offshore integration. However, due to their large heave response, semisubmersibles are not suitable for dry tree applications.
INTECSEA says that the FHSB Semi maintains the advantages of conventional semisubmersibles, and offers favorable motion characteristics of spars to enable the use of TTRs.