+2 votes

Comparison of Spread Moored versus Turret Moored Systems

asked Apr 20, 2014 in Marine by Normandy (21,040 points) | recategorized Jul 29, 2014 by odadmin
  Spread Moored Turret Moored
Vessel Orientation Fixed heading 360weathervaning
Field Layout Prefer flowline arrangement Fairly adaptable, distributed flowline arrangement
Environment Mild to moderate Mild to extreme
Riser System Adapt to various riser systems Location of turret requires special design
Riser Number and Arrangement Can be flexible with additional tie-ins Expansion is limited and required commitment
Vessel Motion Depend on environment/vessel directionality Weathervaning reduces motions
Vessel Arrangement Components spread out and requires extensive interface Compact design and FTL
Offloading Capability Depend on environment/vessel orientation Flexible/adapatable with changing environment
Station Keeping Required larger number of anchor legs Smaller number of anchor legs needed


2 Answers

+2 votes
answered Apr 21, 2014 by Normandy (21,040 points)

Also consider the below key criteria when selecting a type of mooring:

  • Required production uptime and offloading availability
  • Number of risers, well control requirements and power from shore
  • Economics (capital cost versus operating uptime)
  • Hull and other structure fatigue
  • Prevailing met-ocean conditions:
    • Water depth
    • Severity of conditions, nature of severe events
    • Directionality and co-linearity of conditions (dominant direction)
+1 vote
answered Apr 21, 2014 by alsieg (2,780 points)
When selecting a mooring system, CAPEX and OPEX need to be studied and compared side by side to make the best and suitable design for its intended purpose.

CAPEX should take into account: engineering, fabrication and assembly of equipment, installation, procurement, and management costs. Marked up cost may be included as well.

OPEX should include maintenance and inspection interval, replacement of hoses and hawsers, offloading assistance, pilot costs.