volve subsea removal - subopsvolve subsea removal –wellheads cut and recovered to nsg deck....
TRANSCRIPT
Trond Hofseth
Subsea Operations ConferenceHaugesund 08.08.2018
Volve Subsea Removal
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Recovery and disposal of:
➢ STL loading buoy
➢ Mid-Water Arch (MWA)
➢ 9 off mooring lines
➢ Approximately 1.600m of exposed risers
and flowlines
➢ All subsea structures
➢ MWA gravity base structure (3 pieces)
➢ 3 off riser holdback anchors
➢ Drilling template
➢ SSIV
➢ 5 off GRP covers
➢ 10 off wellheads
Volve Subsea Removal – Overall scope of work
Removal of STL Loading Buoy
4Volve Subsea Removal - Cutting of riser and mooring line wire
Volve Subsea Removal – Simops - Recovery of STL loading buoy
Volve Subsea Removal - Towing and lifting the STL loading buoy
Volve Subsea Removal – Lessons learned - STL loading buoy
Lessons learned
➢ Successful vessel simops operation. The method
proved to be a well planned and well performed
operation
➢ During tow of STL the winch readings was approx. 41
tonnes with a velocity of 7.2 knots. This is a higher
speed than expected on this load (ref. tow analysis)
➢ Cutting procedures and subsea tooling worked well,
although the outer plastic layer on riser seems to clog
the diamond wire
➢ Successful use of dyneema sling with additional
protection for towing
➢ Towing calculations conservative with regards to towing
forces
Removal of the Mid-Water Arch (MWA)
Volve Subsea Removal – Mid Water Arch (MWA)
Volve Subsea Removal – Recovery of MWA
Volve Subsea Removal – Lessons Learned - Recovery of MWA
Lessons learned
➢ The vessel crew was well prepared, proactive, selfgoing
and extremely efficient
➢ Communication was excellent
➢ Cutting procedures and subsea tooling worked well
➢ Vessel A-frame with top roller proved to be perfect for the
handling of MWA. This A-frame made it possible to get the
whole MWA on deck instead of towing it to land
➢ Did allow vessel to use own procedures and routines
which improved the operations
Cutting and recovery of 9 off mooring lines
Page footer text | 13Volve Subsea Removal – Mooring line
Page footer text | 14Volve Subsea Removal – Cutting of mooring chain
Observation
➢ Highly trained personell on vessel, correct
equipment on vessel and good planning with input
from vessel crew made this to a very smooth
operation
Lessons Learned
➢ Back filling and loose sediments at the seabed
created bad visibility when Skandi Vega ROV tried
to connect rigging to the chain
➢ Testing and adjusting rotation speed on diamond
blade for cutting of chains is highly recommended
before mobilization
Volve Subsea Removal – Mooring line recovery
Cutting and recovery of flexible export lines
Page footer text | 17Volve Subsea Removal – North Sea Giant
➢ Did cut approx. 1.600m of exposed pipe
➢ 8 inch oil export line and 7.4 inch gas export
line
➢ Cut in 11m sections
➢ The cutter was upended on deck & deployed
vertically
➢ Very efficient, landed onto flexible vertically,
made the cut in 20 second
➢ The shear cutter was also used to lift the
flexible pieces into the subsea baskets
Volve Subsea Removal – Cutting of flexibles using shear cutter
Volve Subsea Removal – Relocation of cut flexibles pieces
Recovery of subsea structures
Volve Subsea Removal – Recovery of subsea structures
Volve Subsea Removal – Design vs actual lift-off weights
Cutting and recovery of wellheads
Volve Subsea Removal – Drilling template recovered to NSG deck
Volve Subsea Removal – Concrete removal at drilling template
Volve Subsea Removal – Concrete removal at drilling template
27Volve Subsea Removal – Cutting of wellheads
➢ Remove riser stumps (incl. tie-back connector)
➢ Drift clean wells internally and install internal cutting tool
➢ Cut through all casings and conductors below mudline
➢ Pull wellhead out of the cement / formation
➢ Recover wellhead to deck
➢ Cutting time approx. 5-6 hours
Volve Subsea Removal – Wellheads and upending frame
Volve Subsea Removal – Wellheads cut and recovered to NSG deck
Summary of vessel operations
VESSEL CAMPAIGN SCOPE DURATION WHEN
Wellservicer C0 Cut loose STL Buoy and MWA, SIMOPS. Cut all 9
chains at pile. Concrete removal at drilling template.
Dredge and relocate GRP covers. General prep work
29 days May/June
2017
Skandi Vega
(CPI)
C1 Tow STL Buoy and MWA to Vats. Recover all 9
mooring lines. Wires on winch and chains in locker
10 days May 2017
North Sea Giant C2 Cutting and recovery of exposed flexibles and risers 15 days Nov 2017
North Sea Giant C3 Release and recovery of 9 off tie-back connectors with
2m riser stumps on top. Cutting and recovery of 10 off
wellheads. Campaign aborted due to perforated
casings
14 days Oct 2017
North Sea Giant C4 Recovery of SSIV, 5 covers, 3 RHA, MWA GBS (3
lifts)
10 Nov 2017
North Sea Giant C3.1 Cutting and recovery of 10 off wellheads and 15 slot
drilling template
16 Dec 2017
Volve Subsea Removal – Summary of vessel operations
AF Decom - Disposal Yard
33Volve Subsea Removal – Disposal summary
CategoryDisposal method In tons
Energy Recovery
Landfill Recycled Reuse Technip Reuse AF Decom Sum
Hazardous waste 1,58 1,28 2,86
Low radioactive waste/Hazardous Waste
3,08 3,08
Metals 2231,83 4590,50 6822,33
Non-Metals 24,12 351,06 375,18
Items sent for inspection to Statoil
31,48 31,48
Saleable 55,16 55,16
Sum 25,70 4,36 2638,05 4590,50 31,48 7290,09
Summary
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➢ Decommissioning more complex than installation (lifting)
➢ Lack of As-Built information, especially from older fields
➢ Concrete removal takes a lot of time (double the time estimated)
➢ Good performance from all subcontractors
➢ Good performance from all three vessels
➢ 6% WOW October through December (North Sea Giant)
➢ Focus on planning as well as flexibility between campaigns and/or vessels required
➢ Great cooperation between Client and TechnipFMC teams
➢ No issues with NORM, but still important to measure
Volve Subsea Removal – Overall lessons learned
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Recovery and disposal of:
➢ STL loading buoy
➢ Mid-Water Arch (MWA)
➢ 9 off mooring lines
➢ Approximately 1.600m of exposed risers
and flowlines
➢ All subsea structures
➢ MWA gravity base structure (3 pieces)
➢ 3 off riser holdback anchors
➢ Drilling template
➢ SSIV
➢ 5 off GRP covers
➢ 10 off wellheads
Volve Subsea Removal – Overall scope of work
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