11 - HMC 5Dec Norwegian Society of Lifting Technology[1]

7/30/2019 11 - HMC 5Dec Norwegian Society of Lifting Technology[1]

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Norwegian Society of Lifting Technology

How can we assist in you r sub sea development

Presented by: Danny Mus

Date: 5 December 2012


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Introduction, How can we assist in your subsea development

Introduction

Presentation contents How can we assist in your subsea development:

- Selection of subsea project from the past

- Typical project phases- Engineering phase

- Transport from yard to offshore site

- Field preparations: Survey and Positioning

- Lower structures through splashzone and set down on seabed

- Offshore Decision making

2


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Subsea Lifting Experience (selection)

3

2005 | Norsk Hydro Ormen Lange

(Heaviest Subsea Template @ 850 msw)

2008 | DSME Tombua Landana

2009 | Hydro O&G Troll & Vega

2010 | BP Block 31

(Worlds Deepest Foundation Piles @ 2,030 msw)

2012 | Total Laggan & Tormore


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Ormen LangeNorway

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Record Lift

Heaviest Subsea Template @ 850 waterdepth


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Client

DSME

Scope

Tower Base Section

Tower Base Template

Leveling Pile Template

Max. Weight

29,500 mT

Water Depth

370 m

Period

Q1 2008

Location

Block 14, Cabinda, Angola

Tombua LandanaAngola

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LEVELLING PILES TEMPLATE

(LPT, 520mT)

-370 m.

waterline

GROUTED

CONNECTION

TOWER BOTTOM SECTION,

TBS, 29,500mT)

GROUTED

CONNECTION

TOWER BASE TEMPLATE

(TBT, 3010mT)

4 No. LEVELLING PILES (315mT each)12 No. FOUNDATION PILES (850mT each)

TOPSIDES ( Total

weight: 30,000T)

TOWER TOP SECTION,

TTS, 7000mT)

Tombua LandanaAngola


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Troll & VegaNorway

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Laggan TormoreUnited Kingdom


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Block 31Angola

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BP Block 31 PSVMExtend of Subsea Scope: Free Standing Riser installation

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9 x Single Line Hybrid Riser (SLHR)


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Riser Base FoundationBallast Module & Driven Pile

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12m

12m

~330mT @ 2,030m


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Lower Riser Assembly

Weight = 23-36mT

Length = 41m


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Upper Riser Assembly

Weight = 60-75mT

Length = 40m


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14

Buoyancy Tank

Weight = 180-240mT

Length = 35-47m

Weight = 180-240 mT

Length = 35-47 m


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Buoyancy Tank Stabbing into Upper Riser Assy


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Install riser string into Riser base Foundation

Steel wire rigging

Riser string weight 500-600 mTRiser length ~1900 m

Polyprop stretcher in rigging


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Rotolatch functionality (1)

17Ready to insert rotolatch(lowering)

rotate rotolatch(lowering)

lock rotolatch(lifting)

A Rotolatch is a locking

/ unlocking device

Load transfer from

steel rigging to

polyprop stretcher

Installation vessel heave is +/- 1m

Riser pre-tension by stretcher.

Stretcher is the absorber to

compensate heave of vessel.


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Rotolatch functionality (2)

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3 pairs of cams

Cam1

Cam2

Toolreleased

Toolengaged

2nd horizontal

left rotation

1st horizontal

left rotation


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Lower complete riser string to locking position in base foundation

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Freestanding Riser Systems: Stabbing Riser

Transferring weight from polyprop stretcher to buoyancy tank

Riser string weight is transferred from steel wire arrangement to

polyprop stretcher arrangement (damping motions)

Heave of vessel is absorbed by polyprop stretcher

Free stabbing Rotolatch connector at seabed

Inserting and locking of Rotolatch in foundation


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Free Stabbing of Riser

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Position and lowerLower and Rotate

Lift and engage

Final position


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Typical Project Phases

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Project Phases and Issues encountered

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Engineering preparation stage

Transport from fabrication yard to offshore location

Field preparations for survey and positioning

Lift structure from barge or SSCV deck

Lower structure through the waterline (splashzone)

Lower structure through the watercolumn

Position and land the structure on the mudline/seabed/template or

foundation already installed

Level structure if necessary

Completion work


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Engineering Preparation Phase

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Typical Subsea Transport and Installation Project, engineering topics:

Barge transport engineering (motion response analysis, grillage and seafastening

design, bollard pull requirement)

Transfer transport unit to SSCV option

Single vs dual crane installation

Anti twist system, anti rotation system

Rigging release systems

Installation engineering (rigging design, dynamic analysis, suction foundation analysis

etc)

ROV detailed scope of work

Survey and positioning detailed scope of work

Handling equipment specification

Installation manual


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Transport from yard to Offshore Site

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Typical Subsea Transport and Installation Project:

Transport from fabrication yard to offshore location

On barge

On SSCV deck

Combination of both (inshore transfer)

Laggan Tormore structures on 400 barge

Vega structures on barge


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Laggan Tormore structures on Thialf

Deck

Tombua Landana TBT on barge H627


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Barge vs Thialf deck transport:

Size and weight structure

Space on deck SSCV

Liftable from deck

Quay location

Access barge vs access SSCV

Workability (lift off from barge vs lift off from Thialf deck)

Offshore lift from barge weather sensitive

Offshore lift from SSCV deck less weather sensitive

Transfer lift to SSCV deck in sheltered waters


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Lift Structure from Barge or SSCV deck

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Lifting the structures from SSCV deck or barge

Pros lift from SSCV deck Pros lift from barge deck

Lift off no critical weather operation Heavier and larger structures can be installed

Preparations to structures direct from SSCV

deck

No height restriction of structure

No barge mooring operations offshore

No people transfer to offshore barge

Rigging attachment less weather restrictive


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Field Preparations, Survey and Positioning

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Installation tolerances drive the field preparations. In order to position the

structure within tolerances (position and heading) a few methods/options can be

distinguished:

1. Positioning via DP and subsea transponder array

2. Positioning via gravity (pre-installed) anchors

3. Subsea infrastructure already present, dock structure over other structure

Each of above mentioned methods have their own accuracy. As back up method

the installation of subsea marker buoys are often used.


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Positioning by Transponders

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1. Positioning via DP and subsea transponder array

Transponder array to be pre installed and surveyed

Transponders on subsea structure for communication with array

ROV interface

Example: Laggan Tormore

Installation Tolerances for positioning SWPS:

Final as built data, position from target:

Structure Position Heading

SWPS +/- 0.50m +/- 2.00

Structure Position Heading

SWPS 0.14m 0.30


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Laggan Tormore Example

Transponder array

Template Target

Typical Survey plot:


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Positioning by Gravity Anchor

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2. Positioning via gravity (pre-installed) anchors

Gravity anchors to be pre installed and surveyed

Sling length determined and custom made

Subsea attachment by ROV

Example: Ormen Lange


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Positioning on Structure

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3. Subsea Structure already present; dock structure over other structure

Docking guides and receptors required for positioning and guiding

Docking loads during installation (steel on steel, docking study)

Subsea connection between foundation and structure

Example: Tombua Landana Compliant Tower, TBT Installation


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Positioning on Structure (2)

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TBT; L*B*H ~ 34*34*22,

W ~ 3010mT

Foundation Piles; L ~ 190m, diam 108

W ~ 850mT each

Barge H-627; L*B*H ~ 177*49*11m


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Installation sequence, TBT landen on LPT

(Levelling Pile Template)

Primary, secondary and tertiary docking pin

engaged

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Tombua Landana Example

Mudline -370 m.


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Lower Structures Through the Waterline

(Splashzone)

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Lifting structures Through the Splash Zone

Dynamic Loads! (DNV-RP-H103) vs design forces

Multiple installation stadia

Structure mass and drag area vs water particle acceleration and velocity,

Hoist wire dynamics, hatch loads, equipment loads etc

Wave force on structure, transferred to rigging and hoists

2 Stages (multiple stages can be defined): Roof just above water and roof just

below waterline:


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Orbital wave motion

Source picture: http://fcit.usf.edu/florida/teacher/science/mod2/beach.profiles.html

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(Splashzone)


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Wave particle motion for deep water described as circles, decreasing with waterdepth:

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Wave orbital motion

Wave period

Waterdepth

Short waves highest effect on slamming

loads but depth effect is large


(Splashzone)


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Wave particle motion for deep water described as circles, decreasing with water depth:


(Splashzone)


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Influence crane tip motions (velocity and acceleration) is very minimal wrt water

particle velocity and acceleration. For a wave period of 6 s, the heave velocity

and acceleration is ~ 2% of the water particle velocity and acceleration!

In other words, the installation vessel hardly moves and slamming loads are

only wave induced, not vessel (motion) induced

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(Splashzone)


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Resulting maximum wave

height based on maximum

allowable dynamics (rigging

design driven, template

design more critical):

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(Splashzone)


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Result is completely

opposite of normal

installation limits.

Normal limits driven by

vessel induced motions

Characterized by:

Hs

43Tp


(Splashzone)


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Effect: short crested waves defined the installation limit

for wave periods around 6 seconds

Low(er) workability!

SSCV is a very large vessel, what is the influence of

the SSCV on the local wave field?

SSCV Shielding study

Shielding effect of SSCV: SSCV, installing a template

on the lee side of the vessel, sheltered from (short

crested) waves.

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Wave

propagation

SSCV

Template


(Splashzone)


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Wave Reflection effects

SSCV Radiation effects

Wave Diffraction effects +

Installation Vessel Shielding Study

Input characteristics

JOHNSWAP Wave Spectrum

6s < Tp < 20s

0 degr < wave heading < 355 degr

Results

Tp = 6s

Wave heading 225 degr (bow quartering)

50% reduction on wave height

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(Splashzone)

Installation Vessel

Wave

propagation


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Set-down structures on seabed

Dynamic Loads vs design forces

Maximum set down velocity on seabed (~ 0.5m/s)

Hoist wire dynamics (max DAF)

Vessel induced motions characterize dynamics,

transferred to rigging and hoists

Mass Spring System, natural behavior defined by:

* mass and added mass template

* waterdepth / reeving length

* Environmental Conditions / crane tip motions(wave induced vessel motions)

* hoist wire stiffness (spring term)

* template drag (damping term)

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Lower Structures

(Set-down on seabed)

Mudline

Crane tip

Motions

Hoist wires

Vessel

Motions

Template

Motions

Waves


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Create model (frequency domain) Thialf, hoist wires, template:

Per wave heading, obtain template heave velocity RAO and

Hoist wire dynamic force RAO.

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Lower Structures



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Create model (frequency domain) Thialf, hoist wires, template:

Per wave heading, obtain template heave velocity RAO and

Hoist wire dynamic force RAO.

For maximum allowable template velocity 0.5m/s and hoist wire dynamics,

define allowable wave height per peak period and wave heading:

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Lower Structures


Hsallowable

Hsallowable

V < 0.5m/s DAF < allowable


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At start of project, wave rider buoy is deployed and directional full spectral

wave and weather predictions obtained.

Decision making tool: compare measurements with predictions, with

RAOs decide on installation window where DAF and set down velocity

will be within limits.

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Lower Structures

(Offshore Decision making)


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Lower Structures

(Offshore Decision making)

Check predicted vs measured

waves (Hs)

Check near bottom vertical heave

velocity template within limits

Check DAF within limits

Date, time

Limiting criterion dynamic force

Limiting criterion heave velocity

Hs

Vheave

Fdyn


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Position template on seabed

When a suitable window is there:

Attach rigging

Cut seafastening

Lift from deck, lower through the

water column and set down on

seabed

Release rigging

Perform hatch operations

Apply suction (if needed)

Completions


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Questions?

Email: [email protected]
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]

Documents

11 - HMC 5Dec Norwegian Society of Lifting Technology[1]