Free-Hanging vs Free-Standing Seabed Mining Vertical ...
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Transcript of Free-Hanging vs Free-Standing Seabed Mining Vertical ...
Free-Hanging vs Free-Standing Seabed Mining Vertical Transport Systems
Frank Lim & Richard Harrison
UMC Bergen11 September 2018
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Overview
Nautilus Minerals DesignBlue Mining ConceptFree-Hanging SystemAlternative – Free-Standing SystemInstallation ConsiderationsSMS or SMnNConclusionQ & A
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Nautilus Minerals Design
One positive displacement pump
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Blue Mining Concept
A number of centrifugal pumps along riser length
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Generic Free-Hanging System
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Contingency actionRemote disconnection packagePump dis-connectable from riser and left on seabedCrawler and pump retrieved separately for maintenance by vessel A-frame
Free-Hanging Single Pump
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Oil & Gas Drilling RiserDisconnectionPackage
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Structural Response Issues with Free-Hanging System
Towing VIV (Vortex-Induced-Vibrations)
Axial Resonance
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VIV Mitigation
Reduce towing speed, which can mean failing to meet production targetConsider VIV suppression strakes along the riser:
adds complexity to the installation of the VTSincreases the overall drag of the systemImpacts operating windows
Connectors on pipe section will need to be more fatigue resistantRequire taper joint at connection to pump to reduced local bending stresses In place monitoring and tracking of fatigue damage
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Alternative –Free-Standing System
Gravity Base anchors riser to seabedLarge buoyancy tank keeps riser standing freelyFlexible hose connects riser top to vesselPump can be disconnected to be retrieved separately from the seabed for maintenance, like the free hanging riser
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Oil & GasFree Standing Risers
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Buoyancy Tank
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Hose Disconnection from Vessel
Contingency actionSurface hose dis-connectable from vesselHose end located by a marker buoyHose retrieved and reconnected on vessel’s return
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Free Standing Riser Hub –Extension System
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Extended Reach & Mine Map
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Installation Considerations
Free-Hanging System Mining vessel needs to have the riser installation/recovery capabilities
Free-Standing SystemInstallation by dedicated vesselLeft subsea semi-permanentlyMining production vessel to relocate itMinimal riser handling facilities on vessel
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SMnN or SMS ?
Picture: NOAA / Flickr
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Seafloor Manganese Nodules
Nodules lie on seabed surface which are harvested by scrapping Fast process and large coverage area to meet economic targetA Free-Standing System will require frequent relocation with associated downtimeFree-Hanging System remains the preferred solution
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Seafloor Massive Sulphides
Surface deep resource requires excavation and crushingSlow processSmall coverage areaWell suited for Free-Standing VTS
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Conclusions
Free-Hanging VTS configuration has so far been the normIt is suited for SMnN extraction because of the speed and large area it needs to coverFor SMS exploitation, a Free-Standing alternative is proposedFree-Standing risers are increasingly common in deep and ultra-deep oil field developmentsThe knowledge and experience are transferable to Seabed MiningIt places much less demand on the mining vessel handling facilities It is safer for the mining vessel !
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