SDV to Deploy SST (14 th April 2016) Subsea Deployment Systems Ltd. - - PowerPoint PPT Presentation

Subsea Deployment Systems Ltd.

SDV to Deploy SST

(14th April 2016)

Subsea Deployment Systems Ltd.

2

INTRODUCTION

• An installation method that overcomes the needs for a heavy lift vessel
• Low risk / low tech / low cost installation method
• Reduced weather sensitivity

Subsea Deployment Systems Ltd.

3

SUBSEA DEPLOYMENT VESSEL (SDV) & SST

Control chain Control tower Tow chain clump weight Castle Subsea Storage Tank (SST) Buoyancy modules Floodable hull Interface frame c/w ballast locker

Subsea Deployment Systems Ltd.

4

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.

Subsea Deployment Systems Ltd.

5

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

Subsea Deployment Systems Ltd.

6

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

Subsea Deployment Systems Ltd.

7

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

Subsea Deployment Systems Ltd.

8

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

Subsea Deployment Systems Ltd.

9

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

Subsea Deployment Systems Ltd.

10

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

Subsea Deployment Systems Ltd.

11

CONTROL CHAIN TOWERS - DYNAMICS

Control chain / towers

• Vertical control
• Lateral control
• Rotational control
• On-bottom weight

Dynamics

• Natural period > 120s
• Response amplitude < 20%
• f surface vessel
• Soft-soft landing

Subsea Deployment Systems Ltd.

12

+

VS

SAFETY AND ENVIRONMENT

Considering like for like operation

• Small number of people directly involved in operation (typ. 1:10)
• Environmental impact considerably less

Subsea Deployment Systems Ltd.

13

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)

Subsea Deployment Systems Ltd.

14

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

Subsea Deployment Systems Ltd.

15

SEASTATE STATISTICS

Subsea Deployment Systems Ltd.

16

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