Ultra deepwater floating production facility for Makassar Strait
Gde Pradnyana
Jafar Korloo
An in-depth comparative analysis of the various dry tree floating systems was carried out for Indonesia deepwater application. The analysis showed that due to the low wave heights and the high persistent surface and deep currents, a spar design may not be the best solution. In addition, a spar was evaluated to have the highest hull costs and high installation costs in this application.
The dry barge concept having risers tensioned by means of buoyancy cans is quite mature and has been proposed for several West Africa deepwater projects. However, the riser tensioning system is complex and may require further specific site investigations.
Considering the low wave height nature of the area, the semi concept offers no major advantage over the dry tree barge concept and it suffers from the same riser system issues as the barge. The maturity of the dry tree semi concept is not at the same level as the dry tree barge.
TLPs, by design, move in surge and sway with wind, waves and currents, but resist heave, roll and pitch because of the fixed length of the tendons. A TLP uses a buoyant hull securely fastened to the seafloor by tensioned tubulars, or tendons. The buoyancy of the hull applies the tension to the tendons. TLPs have been developed and used since the early 1980s in a variety of shapes, configurations, and sizes.
The TLP concept with drilling tender assist proved attractive at West Seno for several reasons.
The key advantages and disadvantages of TLP concept in relation to applications in the Indonesia’s deepwater areas were:
Advantages:
• Heave restraint
• Risers could be locked off to the deck without requiring tensioners
• May be based on nonproprietary design
• Simple hull form
• Low cost hull fabrication
• Could be fabricated in several local yards
• Large number of suppliers resulting in a competitive cost
Disadvantages:
• Weight sensitive
• Costly tendon fabrication, installation, and limited fabricators
• Restraints on sea bed well layout/spacing
• Seabed hydrate commonly associated with deepwater may require additional work in the design of foundation
• Limitation of availability of suitable deepwater installation vessels in the area.
West Seno TLP
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Page 2 of 5
Volume 66 Issue 2
February 2006
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