Prelude, one of the world’s most expensive and technically complex non-naval ships was deployed off north east Australia with the help of tugs and simulation. Shell’s floating liquefied natural gas production, storage and offloading vessel, Prelude FLNG, was positioned off the coast of Western Australia for final commissioning.
This followed a lengthy tow from the Geoje Shipyard in South Korea, by three ocean-going tugs operated by PACC Offshore Services Holdings (POSH) and days of towage simulation. Shell’s huge LNG production facility is 488 m in length and is estimated to have cost US$10Bn to build.
It will be stationed on the Prelude remote gas field, 475 km off Broome, Western Australia, for a minimum of 25 years and was the first FLNG vessel to be ordered. Prelude will be secured to the seabed using prepositioned mooring chains. Once the vessel is secure, it will begin a complex hook-up and commissioning process. Shell expects it to start production in 2018.
Prior to this major towage project, Shell and POSH used simulators in Australia operated by HR Wallingford to plan and practice towage operations. Tow masters, pilots and tug masters were able to familiarise themselves with a realistic simulation of Prelude manoeuvres at sea at the Australia Ship Simulation Centre in Fremantle.
This included real-time navigation simulation for Prelude FLNG’s departure from the Geoje Shipyard, passage through the Busan Channel in South Korea, positioning and mooring Prelude once on site. Simulators were also used to test berthing and departure of LNG, LPG and condensate offtake tankers that will moor alongside the FLNG.
Three powerful, specialised tugs will provide vessel-assist duties. The infield support vessels will remain on station at Prelude, returning only occasionally to Broome for maintenance.
Up to six integrated simulators at the Australia Ship Simulation Centre were used to simulate the FLNG facility and the tugs for the shipyard departure operation. They were used for practising the positioning during connection to the FLNG’s mooring lines, once the vessel was at the installation site.
The simulation models included wind, wave and tidal conditions that were recorded from the site. This enabled crew to test the capability and power of the tugs in advance. Three POSH tugs were attached to the FLNG vessel using 700 m long wires, weighing around 30 tonnes. Tug Deep Orient connected Prelude to its 16 mooring lines at the site.
POSH expanded its fleet with the addition of two Azistern tugs, Posh Husky and Posh Hardy earlier this year for ocean-going towage and harbour duties.
The Australia Ship Simulation Centre opened new premises in Fremantle for navigation and pilot training with Kongsberg simulators earlier this year.