MODU Mooring Installation and Recovery Assistance includes:

  • Modeling line catenaries both real time and in the future
  • Monitoring rudder clearances to anchor handling vessels (AHVs)
  • Assisting with anchor placement for conventionally installed systems
  • Calculating mooring loads for proper load sharing between vessels

Modeling Line Catenaries

Fugro Chance and Delmar worked together to develop the Starfix.Moor program. Using Delmar’s Del-Cat mooring software, Starfix.Moor continually updates and displays in 3-D the catenary shapes of the mooring lines both during installation and recovery in real time. Clearances to any assets (such as pipelines, umbilicals, etc.) are noted and warnings can be seen if these clearances ever fall below approved limits. A screen capture of StarFix.Moor is shown below:

In addition to modeling the mooring catenaries independently to verify the real-time display, Delmar can run the catenaries ahead of time to determine boat positions and payouts necessary to help make safe and efficient connections or disconnections. If too little component is paid out, connections can be too tight for AHVs to make connections safely or rudder contact can occur (see below). If too much is payed out, time is wasted to pay out or haul in excessive component or, if a line is being worked over an asset, safety clearances are typically reduced. Thus, supplying these vessel payouts is critical.

Monitoring Rudder Clearances

As mooring operations are being conducted, it is necessary to ensure that mooring component does not come into contact with the rudders of the AHV. Sometimes it is required for the AHV to turn the boat heading in order to make preset connections and disconnections. If sufficient component is not paid out by the MODU or AHV, rudder contact can occur. This contact can lead to damage to the AHV’s rudder or mooring equipment, which can be especially critical if operations are being conducted over assets.

Anchor Placement

For conventionally installed mooring systems, the anchor is stretched with the AHV after the proper components are payed out by the rig. Therefore, the anchor placement is highly dependent upon the payouts and vessel positions. Delmar can run catenaries in these cases to assist with getting the anchor closer to the proposed position. Modeling the stretch of the line is also important to ensure much of the mooring component is off bottom prior to cutting power on the AHV and setting the anchor in the mud.

Load Sharing

As moored rigs move into deeper water, the weight of the mooring components can become more critical. Deeper water typically requires more component, and the vessels must work with the additional physical weight from suspending more load. For example, for cases where a conventional line is being deployed in deep water, all the heavy chain is paid out and then both the MODU and AHV pay out the necessary wire lengths. If this chain weight is not evenly distributed between the vessels, either the MODU or AHV will have a difficult time paying out if it is supporting too much of the chain weight. Delmar can run catenaries to help ensure that proper load sharing is occurring between the vessels.