phase 4 report - DNV

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RN06: ICE MANAGEMENT – STATE OF THE ART REPORT // Ice ManagementIce Load MonitoringThe vessel was kept on station by the manuallydriven thrusters with the bow continuouslymaneuvering to head into the direction of theoncoming ice. Load could be roughly monitored byassessing the thrust required to manoeuvre the vessel.Performance of Ice ManagementPlanners predicted that the fleet could maintain thedrillship’s station for up to 2 full days. It turned outthat the station-keeping ability was stretched to morethan 9 consecutive days.Experience, learnings and recommendations from theACEX Ice Management operationLearnings from the ACEX project regarding IMinclude:• Dynamic Positioning (DP) isnot possible in heavy ice• Long periods of manual station keepingis not beneficial for the operation• Operational experience regarding requiredmovement of vessel facing ice-drift is essential• It is important to have total integration ofboth drilling and ice management system• Difficult conditions arose when wind speed/ice drift speed stopped and the ice wouldstart to rotate due to the Coriolis effect.• Prop-wash from icebreaker effects positioning2.6. Shtokman Gas Condensate Field, Phase 1SGCF Phase 1Note 1: at the moment of writing the present section,the SGCF Phase 1 Project is at pre-FID stage (presanction).FID stands for Final Investment Decision.Note 2: the present section has been writing bySDAG and remains the courtesy of SDAGThe SHTOKMAN Gas Field is located 610 km fromMurmansk in the Barents Sea. The area is a harshArctic environment. The water depth at location isaround 340 m and the reservoir is 2000 m belowthe mudline. The field reserves are estimated to be3700GSm3. The field will be developed in three<strong>phase</strong>s, the expected production of each <strong>phase</strong>being around 70 million Sm3 per day. ShtokmanDevelopment AG (SDAG) owned by GAZPROM,TOTAL and STATOIL will develop and operate theFirst Phase of the Shtokman gas and condensate field.The offshore facilities of Phase 1 consist mainly ofthe following:• Subsea Production System (SPS).• Umbilicals, Flowlines and Risers (UFR).• Ice resistant and disconnectableFloating Production Unit (FPU).• Trunklines to shore.Drilling is planned to commence approximately twoyears before the FPU arrival on site. Logistics willprovide support in terms of ice-class vessels andaerial means. From the ice management point ofview, there stages are distinguished:• Installation (approximately from earlyMay to late September over 3 years)• Drilling (year around for approximately 3 years)• FPU Operation (year around for 50 years).Ice and Iceberg Management (IIM) Philosophy forthe Installation Stage is as follows:• No installations activities will beperformed when sea ice is forecasted toenter the area of offshore operations• Detection of glacial ice and appropriateoperational measures (threat assessment,alerting, suspension of operations, disconnectionand move off) will be performed. Sincethe probability of iceberg occurrence inthe area of offshore operations duringthe installation stage is very low, physicaliceberg management is not planned.216RUSSIAN–NORWEGIAN COOPERATION PROJECT
RN06: ICE MANAGEMENT – STATE OF THE ART REPORT // Ice ManagementBarents 2020The objectives of IIM during this stage are to:• Ensure safety of the offshore operationsfrom sea ice and iceberg threats• Optimize mobilization timing of marine spread.Specific tasks of IIM during this stage are to:• Forecast potential delay in the beginning of theinstallation season due to the presence of sea ice• Monitor and warn about sea ice edge locationwith respect to the area of offshore operations• Detected icebergs in the areaof offshore operations.Ice Management Philosophy for Drilling Stage is asfollows:• Suspend drilling operations when significant seaice is forecasted and move off the location. Forice-reinforced semi-submersible rig with the riserprotection included, the ice coverage exceeding2/10 th with ice strips / ice floes exceeding 250m is deemed “significant sea ice”. Ice stripsor isolated ice floes less than 250 m will bebroken up using available ice-class vessels inpieces small enough that they pose no threat.• In order to minimize iceberg relateddowntime, it is deemed necessary toperform physical iceberg management,in particular since the resources (anchorhandlers) will be available on site anyway.The objectives of IIM during this stage are to:• Ensure drilling rig safety fromice and iceberg threats• Minimize ice and iceberg related downtime• Minimize/avoid Emergency Disconnections.Specific tasks of IIM during this stage are to:• Carry out sea ice surveillance (detection,tracking & forecasting), using drillingrig(s) as part of the detection network• Carry out physical iceberg management• Break isolated ice patches / floes (intentionallynot called as physical sea ice management)• Alert drilling rig of ice & iceberg hazardsarrival in sufficient time to safely suspendwells, disconnect and move off.Ice Management Philosophy for the FPU OperationStage is as follows:• The FPU will be designed as an ice resistant(Arc 5 with additional strengthening for icereversal situations and iceberg impacts) anddisconnectable production unit able to withstandindependently almost all ice and icebergactions expected to occur at Shtokman. Theseconditions are called design limits and acceptableresponse criteria under these conditions andinteraction scenarios will be satisfied.• An additional safety margin will be applied tothese design limits to define the FPU operationallimits (OPL). Any ice feature or ice situationforecasted to exceed these operational limitsis considered an ice threat to the FPU.• Ice management will be used to detect andmitigate sea ice and iceberg threats to minimize/avoid production downtime. If an ice threatcannot be managed in time, appropriatedisconnection procedures will be initiated.• Two types of disconnection procedures havebeen identified based on available time:planned disconnection (PDC) and emergencydisconnection (EDC). The duration of PDCis in the range of 5 to 6 hours. When theice threat is discovered late, emergencydisconnection (EDC) will be initiated. Thisprocedure will not take more than 3 minutes(excluding time required for decision making).• If, during PDC or EDC, the ice threat isaverted, the procedure can be reversed inorder to resume production. On the otherhand, if during PDC the ice threat gets tooclose (in terms of distance or time), therecan be transition from PDC to EDC.• Initiation of the FPU disconnection is based onforecast of the adverse ice effects, while triggeringof the final disconnection step (MRB release) willbe based on the real-time situation monitoring.The primary objectives of IIM during this stage areto:• Ensure FPU safety from sea ice and iceberghazards by detecting and tracking icethreats Minimize FPU downtime due tosea ice and icebergs by forecasting andperforming physical management.The secondary objectives of IIM during this stage areto:• Ensure safety and efficiency of marineoperations, in ice and icebergs infestedwaters (for instance route planning, icebergavoidance, assistance for load transfers)• Assist FPU during transit and reconnection in ice• Assist emergency EER from theFPU in ice conditions.Report no 2012-0690 217
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Barents 2020Barents 2020Assessment
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Barents 20206. Contents of Risk Man
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Barents 2020CONCLUSIVE SUMMARYThe B
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RN02: DESIGN OF FLOATING STRUCTURES
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