phase 4 report - DNV

RN06: ICE MANAGEMENT – STATE OF THE ART REPORT // Ice Managementthe SALM to the seabed was about 36 hours. Hencethe IM management team had to ensure that nohazardous ice arrived at the SALM site within thistime. Short time forecasts of 3 to 10 hours were alsorequired to support SALM raising operations in thespring.The forecast model was calibrated by comparingthe ice drift measured from radar, for the 24 hoursbefore the forecast date and time, to the calculatedice drift. Ice drift was also obtained by comparing thelocations of the same floes in Terra MODIS satelliteimages obtained over two or three consecutive days.Terra Modis images were received daily when thevisibility was good.Physical Ice ManagementPhysical ice management was provided primarilywith three vessels. There was a dedicated ice breakerwhich was used as a scouting vessel to the North ofthe island to warn of approaching dangerous ice.When the SALM raising or lowering operation wasimminent, the scouting icebreaker would come closerto the site to assist with the ice breaking. A primaryice breaking vessel was situated 1-3 miles from theSALM area and broke ice on the drift line as reportedhourly by the team on the Molikpaq platform to asize that could be handled by the primary protectionvessel. An azimuthing ice breaking supply vessel wassituated a few hundred meters ahead of the SALMon the drift line and provided a flushing operationusing her thrusters angled out in opposing directionsand operating at high power levels to clear an area ofwater wider than the SALM and FSO from ice.Procedures for Threat EvaluationThe threat of dangerous ice was evaluated by theice management team. Firstly they evaluated thedangerous ice that was around to the North of thesite, up to the Northern most point of the Island, andthen assessed the likelihood and the timings for itcoming to site. If it was likely to drift outside of theSALM area then it was only monitored for changesin drift. The operation for raising or lowering theSALM and keeping the FSO connected to the buoywas evaluated and ‘T’ times were developed whichwere the times required to remove the assets to aplace of safety (i.e. lower the SALM back to theseabed and take the FSO to an area with ice thatwould not damage her hull.) The Ice ManagementTeam then issued daily ice alerts which advised the‘T’ time available, the dangerous ice in the area andthe likelihood of it impacting the site.Procedures for disconnectionThe FSO and export tanker could disconnect quicklyfrom the site as Camlock flanges were fitted on theend of the export hose from the FSO to the exporttanker and the hose was mounted on a reel on the aftend of the FSO for faster recovery. The FSO couldrapidly disconnect from the SALM as there was aquick disconnect coupler fitted and the SALM hosecould be lowered quickly and buoyed off. There wereremote operated bow mooring hooks which couldrelease the FSO from the SALM and the vessel couldmove off within minutes if necessary although amore controlled disconnect was preferred.The SALM took longer to lower to the seabedand was a complicated procedure which relied on thetide flowing in the correct direction so as to avoiddamaging the bottom swivel bearing which had to belaid down in a 40 degree segment only. Around 18hours as a minimum was required for a controlledlaydown so the preference was to defend the SALM ifpossible with the ice breakers. The weak point of theSALM was the export hose which exited the SALMaround 2.5 – 4m below the sea surface (depending ontide) which could be crushed and damaged by any icepassing through with a deep enough keel.Organization, Responsibilities and ProceduresThe Ice Team consisted of 9 individuals with manyyears of operational ice experience. The Ice Teamleader, the Ice Management Director (IMD) workedon the FSO and reported in to the Marine Managerand he presented a consolidated view from the iceteam in order to present the management teamwith only one position to avoid confusion. Twoship masters with experience in ice managementassisted the captain on the ice breaker and onone of the support boats. Their job was to reviewthe ice situation at all times and advise the ships’captains and the IMD where appropriate. One iceobserver was placed on the ice breaker, to developice maps of the ice around and at some distancefrom the Molikpaq. Three Ice Observers worked onthe Molikpaq to collect ice drift data using marineradar and as a central data collection team. One IceObserver remained nearby shore base and heliport,to conduct helicopter ice reconnaissance’s whenrequested. The satellite image provider also providedanalysis of ice drift further away from the site whenrequested and where there were identifiable icefeatures. All vessels and personnel were in constantcommunication via internet, marine radio, andtelephone.TrainingThe ice team members were all experienced icescientists before coming to site. There was an icemanagement manual developed which had themethodology described for all of the processes used.The ice team was assembled a couple of weeksbefore the operations were due to commence andtherefore had time to review this manual, sort out214RUSSIAN–NORWEGIAN COOPERATION PROJECT