Innovative Response Forecasting Leads to Increased Gangway Connectivity on Safe Zephyrus

23/11/2016 01:07

Increase in gangway connectivity was achieved by using the Deep Sea Mooring and StormGeo response forecasting tool on Safe Zephyrus, leading to substantial cost savings.

One of the most important tasks for offshore accommodation vessels (flotels) today is providing a safe passage for personnel to the host installation. In such cases, the accommodation vessels are positioned alongside the rig and connected by means of a telescopic gangway. 

Yet, despite the latest dynamic positioning (DP) systems on the accommodation vessels, unpredictable weather and the understandable need to err on the side of caution means that in questionable conditions such gangways are often non-operational. 

"Historically the decision on whether or not to connect the gangway has been down to the seamanship of the team on board who operate according to a specific guidelines," said Captain James Suffield, Master & Offshore Installation Manager of the Safe Zephyrus accommodation vessel.

"These include a free range of heading movement of around 90 degrees and a maximum telescopic movement of the gangway of no more than +/- seven meters before disconnection is required."

Yet, what if you could estimate the movement of the vessel based on the latest weather forecasts and highly accurate predictions on how such floating units will respond?

Such a scenario is becoming a reality through an innovative partnership between Deep Sea Mooring (DSM) and StormGeo, a provider of decision-support services for weather sensitive operations.

DSM combines state-of-the art hydrodynamic software and weather forecasts to accurately predict the relative movement of the flotel and the gangway stroke to the attached platform. The result is the ability to forecast gangway motion, maximize availability, reduce risk, and optimize operations.

One such pilot is taking place on Prosafe’s Safe Zephyrus, one of the world’s most advanced and versatile accommodation units capable of operating in the harshest environments and to the highest standards of safety.

The vessel is equipped with a DP3 system, can accommodate 450 persons, and is at the time of writing supporting Aker BP (formerly Det norske oljeselskap ASA) in the Ivar Aasen Project field in the Norwegian sector of the North Sea. The field is 100 miles south west of Stavanger in harsh offshore conditions (especially in winter) where wave height is rarely below four meters.

Captain Suffield continues: "The predictive software and DSM’s engineering expertise has been very helpful to us in determining the best heading and optimal loading required to maintain gangway connections. Whereas previously in marginal weather states, we have perhaps disconnected too early, now we have the necessary information to optimize connectivity while still adhering to the highest safety standards."

The result is that over just two months, gangway connectivity has increased by an extra 2 per cent compared to previously. Taking into account that the Safe Zephyrus houses 450 personnel - all on high day rates - as well as the rig and support vessel hire costs, the increased connectivity is leading to substantial cost savings.

The knowledge-based information generated from DSM and StormGeo is also very useful in helping plan longer-term support vessel operations. Captain Suffield again: "The information allows us to change heading when required and is particularly useful when simultaneous support and supply boat operations are taking place. The result is more efficient operations."

And there is more to come. Captain Suffield concludes: "We are continuing to fine-tune the information we receive and combining it with other hydrodynamics and power management data to even better predict vessel movement. Supporting helicopter logistics is also an option as well. What is clear to us so far, however, is that the forecasting system provides significant potential for operators."