Fully Submersible Heavy Lift Vessel

Size: px

Start display at page:

Download "Fully Submersible Heavy Lift Vessel"

August Jacobs
6 years ago
Views:

1 Fully Submersible Heavy Lift Vessel Arnbjorn Joensen Oil and Gas Authority (OGA) (15th February 2016)

2 CONTENT Leadon structures demobilisation Competitiveness (case studies) Decommissioning options Installation options 2

3 LEADON 3

4 TOWHEAD A - NORTH Length 29.0m (32.0m incl. carrier) Width 6.6m (excl. cut spool ends) Height 4.6m (excl. shoes and flooding cages) Weight 231.5Te (wet and in place weight) 270Te (dry, excl. trapped water) 4

5 MIDLINE STRUCTURE Length 22.0m (28.0m incl. carrier, excl. off MLS buoyancy) Width 6.0m Height 4.6m (excl. shoes and riser bases) Weight 200.0Te (wet) 230Te (est. dry, excl. trapped water) 5

6 TOWHEAD B - SOUTH Length 26.0m (29.0m incl. carrier) Width 6.6m (excl. cut spool ends) Height 4.6m (excl. shoes and flooding cages) Weight 204.0Te (wet and in place weight) 235Te (est. dry, excl. trapped water) 6

SRF (BUOYANCY TANK) MAIN PARTICULARS Potential for smaller unit if towhead was partially dewatered Stability during load transfer to be checked if lifted solution Length 40.

7 SRF (BUOYANCY TANK) MAIN PARTICULARS Potential for smaller unit if towhead was partially dewatered Stability during load transfer to be checked if lifted solution Length 40.0m Width 12.0m Height 4.6m (9.0m incl. towers) Mass 150Te, Displacement 450Te, Capacity 300Te System would be fitted with transponder and monitoring equipment Fenders / bumpers piping not shown 7

8 SRF (BUOYANCY TANK) MAIN COMPONENTS Tow Chain Clump Weight Control Chain Control Tower Castles Ballast Lockers Leadon Structure Floodable Tanks 8

9 PREPARATION WORK All flooded member valves in open position Structure pre-rigged with lift rigging Prepare structure with pins / interface arrangement Deploy contingency weight to be used as extra securing in case mass / displacement estimation is wrong 9

10 SET DOWN IN FIELD Adjust tow speed and tow wire to maintain SRF at required depth Slow down when approaching field to lower the system Pay out tow wire to lower tow chain clump weight on to target System will float well above seabed (within range of the Structure) 10

weight on seabed) Lower SRF on to structure by paying out on the control chains

11 DOCK ONTO STRUCTURE Lower control chains into the control chain towers Slew crane to create lead on control chains Pay out chain until the system is neutral (chain weight on seabed) Lower SRF on to structure by paying out on the control chains When landed on structure pay out control chain into control chain towers and disconnect 11

12 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 12

13 DOCKING AND INTERFACE Pin arrangement (pre-installed interface) Supports Latching System Slings (back-up) 13

RAISE STRUCTURE WROV to connect SRF to structure with interface connectors Deploy hoses and de-ballast compartments Deploy control lines and reconnect to the control chains

14 RAISE STRUCTURE WROV to connect SRF to structure with interface connectors Deploy hoses and de-ballast compartments Deploy control lines and reconnect to the control chains Slowly raise the control chains until SRF and structure are rising When clear of seabed, fully recover control chains Note: Excess buoyancy at one end to break-out the structure. 14

15 SUBMERGED TOW Tow chain clump weight balances the subsea deployment vessel 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 AHT tows the subsea deployment vessel back to shore 15

16 Submerged tow Recover chain for surface tow Support / Work Boat De-pressurisation TOW 16

17 LOAD IN All valves open to let drain Pre-rigged with lift rigging Terex Demag TC will have approx. 370Te cap. Pins/interface operation 17

18 Submersible barge Floating dock / dry dock Float off and Lift OTHER LOAD IN METHODS 18

19 19

20 20

21 POSSIBLE VESSEL 12 AHTs on the spot market with WROV Other 30+ AHTs on the spot market 21

22 Lerwick Shore Crane / Subm. Barge 95nm DEMOB LOCATIONS Bergen Dry dock 130nm Nigg Dry dock 210nm Haugesund Dry dock 110nm Rosyth Dry docks 270nm Stavanger Dry dock 135nm 22

23 Based on Lerwick Quay SCHEDULE DSV in field to prepare and support during hook-up Tow speed approx knots Does not consider other DSV work in field 23

Negligible dynamic loading Structures are not recovered to deck Reduced

24 SAFETY AND ENVIRONMENT Low tech / fail safe Operations can be suspended at any time (no point of no return) Operations insensitive to weather Negligible dynamic loading Structures are not recovered to deck Reduced risk of catastrophic loss Fewer personnel involved Low carbon footprint + VS 24

25 SEASTATE STATISTICS Subject to operational windows and seasonal variations 25

26 INHERENT SAFETY Total loss minimised Close to neutral No point of no return Rigging failure Buoyancy loss TOW WIRE FAILURE (10x) 26

27 COMPETITIVENESS (CASE STUDIES) 27

CONVENTIONAL METHODS Heavy lift vessel (semi submersible) Day cost base > $900 000 Transit speed <

Constrained project scheduling Heavy lift vessel (shipshape) Day rates > $200 000 Transit speed >

28 CONVENTIONAL METHODS Heavy lift vessel (semi submersible) Day cost base > $ Transit speed < 7 knots (mob/demob expensive) Can lift in relative rough weather (off deck) Limited availability Constrained project scheduling Heavy lift vessel (shipshape) Day rates > $ Transit speed > 13 knots Weather sensitive Hs < 1.5m Limited capacity in ultra deep water Only few with DP capability 28

29 GORGON-JANSZ ( ) 29

30 SHTOKMAN ( ) 30

31 DECOMMISSIONING OPTIONS 31

32 SKIP / PIPE RACK Skip with SRF interface can be placed at towhead locations May be filled with mats, spools and other rubbish Avoids multiple and risky lifts to DSV/RSV deck Similar interface may be created to transport bundle sections 32

33 SKIP Skip hold can be de-ballasted to bring it to shallow draught Skip can be used for both subsurface and surface transport Demonstrated skip Length Width Depth Weight 32m 16m 8m 300Te Capacity (sub) 300Te Depth rating* 150m * May be deeper if upper tubulars are pressurised 33

Side and Double Bottom Tanks (high point open to the sea) Upper tubular (fully

34 Remotely operated (Valves will be operated remotely for de-ballasting) SURFACING Hold (water can be pumped out of the hold using pressurised air from lower tubular) Side and Double Bottom Tanks (high point open to the sea) Upper tubular (fully sealed, buoyancy equals submerged weight of skip) Lower tubular (c/w ballasting facilities) 34

35 INSTALLATION OPTIONS 35

36 U-SHAPE WITH INTERFACE FRAME 36

37 U-SHAPE WITH INTERFACE FRAME Templates / manifolds Opportunity to increase slots Suction cans vs. mudmats 37

38 SUBSEA COMPRESSION (MODULES) 38

39 DEEPWATER SDV / SKIP SDV hold can be de-ballasted to bring it to shallow draught SDV can be used for both subsurface and surface transport 39

40 SUBSEA STORAGE UNIT 40

Fully Submersible Heavy Lift Vessel

Fully Submersible Heavy Lift Vessel Arnbjorn Joensen Aberdeen Maritime Branch (28th January 2015) PRESENTATION Introduction to the Subsea Deployment Vessel Installation method Tank test video Potential