SDV to Deploy SST (14 th April 2016) Subsea Deployment Systems Ltd.
Subsea Deployment Systems Ltd. INTRODUCTION • An installation method that overcomes the needs for a heavy lift vessel • Low risk / low tech / low cost installation method • Reduced weather sensitivity 2
Subsea Deployment Systems Ltd. SUBSEA DEPLOYMENT VESSEL (SDV) & SST Control chain Buoyancy modules Tow chain clump weight Control tower Castle Interface frame Floodable hull c/w ballast locker Subsea Storage Tank (SST) 3
Subsea Deployment Systems Ltd. INSTALLATION SCENARIOS Base Case • SST filled with fresh water giving a net weight of 1500t Optional Case • SST filled with oil giving a net weight of 200t In both cases the installation method will be similar but a smaller SDV would be used for the optional case. 4
Subsea Deployment Systems Ltd. SDV MAIN PARTICULARS • Length 35.2m • Width 29.2m • Depth 5.0m • Overall height 13.0m (Est. 21.5m incl. interface frame) • 408 no. 3x3x1m buoyancy modules • Steel 525t • Scrap chain 1800t • Displacement 3400t 5
Subsea Deployment Systems Ltd. OUTLINE INSTALLATION METHOD Load out • Dock on interface frame • Flood and lower the SST below the surface • Float SDV over and connect to SST • Flood and lower the SST until fully supported by the SDV • Disconnect inshore HLV 6
Subsea Deployment Systems Ltd. OUTLINE INSTALLATION METHOD Tow • Shallow water tow • Flood of all tanks and piping • Surface tow with nominal buoyancy • Deploy tow chain and fully submerge the assembly 7
Subsea Deployment Systems Ltd. OUTLINE INSTALLATION METHOD Approach • Adjust tow wire and tow speed to slow down upon approach to site • Lower tow chain clump weight on to temporary target with SST in range of final target 8
Subsea Deployment Systems Ltd. OUTLINE INSTALLATION METHOD Landing • Lower control chains into control towers • Pay-out until the system is neutral and lower the assembly on to target • When landed lower control chains into control towers and temporarily disconnect • Install ballast equivalent to SST weight • Disconnect SST from interface frame • Reconnect to control chains • Raise SDV clear of SST by raising control chains • Pull control chains clear of SDV 9
Subsea Deployment Systems Ltd. OUTLINE RECOVERY METHOD Recover SDV • Tow chain clump weight anchors the SDV • Recover wire to bring the chain clear of the seabed and slowly move forward • Increase tow speed and adjust tow wire until SDV at suitable depth 10
Subsea Deployment Systems Ltd. CONTROL CHAIN TOWERS - DYNAMICS Control chain / towers • Vertical control • Lateral control • Rotational control • On-bottom weight Dynamics • Natural period > 120s • Response amplitude < 20% of surface vessel • Soft-soft landing 11
Subsea Deployment Systems Ltd. SAFETY AND ENVIRONMENT Considering like for like operation • Small number of people directly involved in operation (typ. 1:10) • Environmental impact considerably less VS + 12
Subsea Deployment Systems Ltd. INHERENT SAFETY General • Total loss minimised – “close to neutral” • Insensitive to weather • No point of ‘no return’ Rigging failure • No catastrophic loss Tow wire failure (10x) 13
Subsea Deployment Systems Ltd. VESSELS • Currently 10 AHTs on the spot market with WROV fitted • Some with offshore crane (crane not strictly required) • All with DP II capability and BP > 220t • Other 30+ AHTs on the North Sea spot market 14
Subsea Deployment Systems Ltd. SEASTATE STATISTICS 15
Subsea Deployment Systems Ltd. SUMMARY • Largely failsafe and very low tech • Larger weather window (wave & ice) • Potentially greater availability compared to HLVs • Potential for phased installation when not relying on HLV • Technology is considered “disruptive” by major contractors • SDS is looking for an opportunity to develop the concept into a working solution 16
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