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Deepwater Pipelines Design for Installation and Operation

Pavia, November 21st, 2014

Roberto Bruschi – [email protected] Marchionni – [email protected] Parrella – [email protected] Maria Bartolini – [email protected]

Deepwater Pipelines Design for Installation and Operation – Pavia, November 21st, 2014

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CHALLENGES BY DISCIPLINE …

2

FLOW ASSURANCE

SEABED MECHANICSMECHANICAL

DESIGN

OCEAN ENGINEERING

DESIGN FOR INSTALLATION

DESIGN FOR OPERATION

PIPELINE INTEGRITY

MANAGEMENT

MATERIALS & WELDING


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MECHANICAL DESIGN – MEETING DEFINED SAFETY TARGETS

3

Design guidelines such as ISO and DNV OS-F101 adopt a LRFD (Load Resistant Factor Design)approach relating failure modes and consequences to “Safety Class” categorization. A set of limit state design formats, including partial safety factors for both load and resistance, are

defined. The partial safety factors to meet a predefined safety target have been calibrated using structural

reliability methods.Reliability methods applied directly to specific structure, avoiding the use of pre-established partialsafety factors, are allowed and sometimes recommended.

SLS serviceability limit state ; ULS ultimate limit state; FLS fatigue limit state; ALS accidental limit state

DNV OS-101 2013


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Load and Resistance Factors Targeting given Safety Level

LIMIT STATES DESIGN FORMAT

Ld( F, C S) < Rd (SC m)where:

Ld design load effect functionRd design resistance functionC condition load factor environmental load factorF functional load factorS system safety factor resistance usage factor

Prob

abili

ty D

istr

ibut

ion Resistance

Distribution, R

Load Distribution, L

Nominal Load Nominal Resistance

Nominal SafetyDomain

fL>1 fR<1

5

MECHANICAL DESIGN – DEFINITION OF RELEVANT LIMIT STATES

The limit state format is a functional relationship including any parameter influencing the relevant failure mode


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MECHANICAL DESIGN - LRFD DNV OS-101

ULTIMATE LIMIT STATES (ULS): Bursting / Pressure Containment Collapse Propagating Buckling Local Buckling due to Combined Loading (DCC and LCC) Fracture/Plastic Collapse/ Ductile Tearing of Defective Girth Welds Ratcheting (accumulation of plastic deformation in case of excessive

bending at the S-lay Stinger) SERVICEABILITY LIMIT STATES (SLS): Ovalization Limit due to Bending

FATIGUE LIMIT STATES (FLS) ACCIDENTAL LIMIT STATES (ALS)

7


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MECHANICAL DESIGN - LRFD DNV OS-101 (BURSTING LS)

Note:cont = Density pipeline contentPb = B ursting PressureD = D Nominal outside iameterfy = SMYS ’tnom = Nominal wall thickness of pipe (un-corroded)tfab = F abrication thickness tolerancetcorr = C orrosion allowance

Minimum wall thickness for pressure containment/bursting according to DNV OS F101 design criteriaThe criterion shall be fulfilled in both Operating and System Pressure Test conditions at the applicable water depths.

mSC

beli

tppp

)( 1

pb(t1) Pressure Containment Resistancepli Local Incidental Pressurepe Local External Pressuresc Safety Class Resistance Factor

as per Tab. 5-5 of DNV RP F101m Material Resistance Factor

as per Tab. 5-4 of DNV RP F101

According to DNV OS F101 Sect. 3 B305, the incidental over design pressure ratio, inc, can be set to 1.05, which is the minimum allowed ratio, provided that the requirements to the Pressure Safety System are satisfied.This implies that the Pressure Safety System shall guarantee the maximum incidental pressure does not exceed the design pressure by more than 5%.

contincdli hgpp

8

fabnom

corrfabnom

uub

ysb

ubsbb

contincdli

ttt

tttttx

fxD

xxp

fxD

xxp

xpxpxphgpp

××

××

×××

1

1

1

,

,

,,

TestPressure

lOperationa

32

15.12)(

322)(

))();(min()(


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scm

ce

tppp

1min

tDfppppppp opelcpcelc 22

3

21

2

DtE

pel DDD

fominmax

Pe External Pressure

Pmin Minimum Internal Pressure(zero for installation except in case of flooded pipe)

Pc Characteristic Resistance to External Pressure (collapse)

sc Safety Class Resistance Factor as per DNV OS-

F101 Tab. 5-5m Material Resistance Factor

as per DNV OS-F101 Tab. 5-4

Note:D Nominal Outside Diam.Dmax Maximum In/Outside Diam.Dmin Minimum In/Outside Diam.U Material Strength Factor

t1 = tnom – tfab (Install & Hydrotest)t1 = tnom – tfab – tcorr (Operating)tnom Nominal Steel Wall Thicknesstfab Fabrication Thick. Tolerancetcorr Corrosion Allowance

Plastic Collapse Pressure

OvalityElastic Collapse Pressure

DtSMYS = p

ofabUp

22

MECHANICAL DESIGN - LRFD DNV OS-101 (COLLAPSE LS)

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12

2c

mineSm

22

2pc

SdSm

2pc

SdSm

tppp

tSS

tMM

CC

C

220 ttDf = S yP

2

2

tD

pp

f = 1-pp 1-

pp o

p

C0

p

C

el

C

ttDf = M yP 22

20




c Flow Stress Parameter

MSd Design Moment

SSd Design Effective Axial Force

sc Safety Class Resistance Factor as per DNV OS-F101 Tab. 5-5

m Material Resistance Factoras per DNV OS-F101 Tab. 5-4

Plastic Axial Capacity

Plastic Bending Capacity

Note:D0 Nominal Outside Diam.U Material Strength Factor

t2 = tnom (Install & Hydrotest)t2 = tnom – tcorr (Operating)tnom Nominal Steel Wall Thicknesstcorr Corrosion Allowance

y

uc f

f 1

600

601590

60

155.0

2

0

2

020

2

0

tDfor

tDfortDt

Dfor

Collapse Pressure• f0 = f(Dmax, Dmin, D0)

• pel = f(E, D0, t)

• pp = f(SMYS, U, fab, D0, t)

MECHANICAL DESIGN - LRFD DNV OS-101 (LOCAL BUCKLING LS LCC)

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23

,0

278.0dh

gwC 0.01 -

Dt =

SMTSSMYS

dh max,

60

6020100

200.1

200.1

2

0

2

02

0

2

0

tDifdefinednot

tDif

tD

tDif

gwGirth Weld

Factor

Yield to Tensile Strength Ratio

Note:D0 Nominal Outside Diam.t2 = tnom (Install & Hydrotest)t2 = tnom – tcorr (Operating)tnom Nominal Steel Wall Thicknesstcorr Corrosion Allowance

2

2

tD

pp

f = 1-pp 1-

pp o

p

C0

p

C

el

C

Collapse Pressure



c Characteristic Bending Strain Resistance

Sd Design Compressive Strain


sc Safety Class Resistance Factor as per DNV OS-F101 Tab. 5-5

m Material Resistance Factoras per DNV OS-F101 Tab. 5-4

Resistance Strain Factoras per DNV OS-F101 Tab. 5-8

1 tp

pp + t C

eSCm

C

Sd

0.8

2

min

2 0,

• f0 = f(Dmax, Dmin, D0)

• pel = f(E, D0, t)

• pp = f(SMYS, U, fab, D0, t)

MECHANICAL DESIGN - LRFD DNV OS-101 (LOCAL BUCKLING LS DCC)

11


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13

FLOW ASSURANCE


DESIGN

OCEAN ENGINEERING



PIPELINE INTEGRITY

MANAGEMENT

MATERIALS & WELDING


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The relevant failure modes and limit states for offshorepipeline installation are the following:

Collapse due to external pressure. Buckle propagation due to the external pressure in case of buckle

initiation. Local buckling due to external pressure and bending at the sagbend and

due to tensioner and bending on the stinger in case of S-Lay installation orin flute of the J-Lay tower.

Concrete crushing at the stinger in case of S-lay technology. Plastic collapse & fracture of defective girth welds. Fatigue damage of the girth welds due to severe loads and long time

interval from ramp exit to touch down point.

DESIGN FOR INSTALLATION – RELEVANT LIMIT STATES

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DESIGN FOR INSTALLATION - PIPE “S” AND “J” LAYING

stinger

overbend

sagbend

Touch downpoint

Stinger tip

Shallowwater

S-laying: consists of assembling the pipe jointson the horizontal ramp of the lay vessel.• Even for large diameter pipes, 2-4 (6) km/day• High curvature applied on the overbend• High tensioner forces required to hold the pipe in suitably “S”

shaped lay spanSea bottom

touchdownpoint

sagbendstinger tip

Shallowwater

J-laying: the pipe departs from the lay vessel ata near vertical angle, hanging like a cable andgently curving towards the horizontal as itapproaches the seabed.• Low tension forces required to hold the pipe in suitably “J”

shaped lay span• Slow lay rate, 2-3 (5) km/day• Low curvatures of the lay span

Rationale for safe installation of subsea and sealines: pipeline lay operation mode lay equipment vessel strength/stability capacity calculation

15


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DESIGN FOR INSTALLATION - CRITERIA

Laying Criteria aiming to define allowable moments and strains is the following:

At the Overbend region (mainly S-Lay): Strain (DNV OS – F101) Simplified Criteria Strain (DNV Design Guideline) Design Criteria Allowable Bending Moment (JIP Design Guideline) Design Criteria

At the Stinger Tip (mainly S-Lay): Allowable Bending Moment (DNV OS – F101) Design Criteria No contact to the Stinger Tip (Recommended Practice)

At the Sagbend region (both S & J-Lay): Bending Moment (DNV OS – F101) Design Criteria (2)

Bending Strain (JIP Design Guideline) Design Criteria Bending Strain of 0.15% (API Recommended Practice) Design Criteria (3)

1. The red one are generally used.2. Load Controlled Condition (LCC) i.e. Bending moment criterion is generally used in Shallow Waters.3. Displacement Controlled Condition (DCC) i.e. Bending strain criterion is generally used in Deep Waters.

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DESIGN FOR INSTALLATION - J-LAY LOAD CONDITIONS

vessel

Residual Lay Tension

RollersReactions

Seabed Reaction

Current

Waves

Pipe Submerged

Weight

TensionerTension

The required residual lay tension is low due to the very large αexit(~90 deg). Rollers reactions are

due to pipe lay pull (not to pipe weight). Tensioner tension is a

function of pipe column weight.

αexit

WD

Thruster

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Mean sea level

Sagbend

Stinger Tip

Overbend

Sea Bottom

Bottom Tension

Bollard Pull(Propeller Capacity)

Tensioner Tension

Stinger Radius

From: • Average Stinger Radius Exit Angle• Allowable Strain at Stinger Wall ThicknessTo:• Top Tension Tension Capacity• Bottom Tension Propeller Capacity

Main Relationship:• STT~ BT + SW*WD - BK2/2Where:STT is the stinger Tip TensionBT is the bottom tensionSW is the submerged weight per unit length WD is the water depthB is the bending stiffnessK is the pipe curvature at the point

where STt is applied

Water Depth

TDP

DESIGN FOR INSTALLATION - S-LAY LOAD CONDITIONS

18

Touch down point Shallowwater


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M =f(Rstinger)F = f(N, Rstinger)

N = ½ EJ * k2 + RLT + WD*SWeight

N

M

F

DESIGN FOR INSTALLATION - S-LAY LOCAL LOAD CONDITIONS

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DESIGN FOR INSTALLATION - S-LAY LOCAL LOAD CONDITIONSPi

pe C

urva

ture

Am

plifi

catio

nB

endi

ng S

trai

n(%

)

The amplification of the pipe local curvature increasesconsidering a concentrated contact (1 roller vs. 4rollers) and reducing the stinger curvature radius

20


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40.6

33.9

29.0

25.4

22.6

35.6

28.4

23.7

20.3

17.8

25.4

20.3

16.9

14.5

12.7

20.3

16.3

13.5

11.610.2

15.2

12.210.28.77.6

IGE

SEVERE LAYING

MILD LAYING

0.0

0.5

1.0

1.5

2.0

2.5

3.0

10 15 20 25 30 35 40 45OD"

Forc

es (M

N)

29.3 tF yelastic Generally:• for pipeline exposed to frequent point load events (occurrence >=

10-4 per year per km)

16”<OD<20” : 14 mm wall thickness20”<OD<36” : 16 mm wall thicknessOD>36” : 18 mm wall thickness

• for pipeline not exposed to frequent point load event

10<OD<16” : 10 mm wall thickness16<OD<20” : 12 mm wall thickness

OD (inches)FO

RCE

(MN

)

29.3 tF yelastic

DESIGN FOR INSTALLATION – MINIMUM PIPE WALL THICKNESS

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DESIGN FOR INSTALLATION - ANALYSIS

Tasks Tools/AnalysisActivitiesInputs

Installation Project

Stinger Settingvs.KP

• Normal Laying• Initiation / Lay-Down• Abandonment & Recovery• Stinger Movimentation• Accidental Flooding• Vessel Loss of Position

Limit Sea State Conditions

vs.Pipe Dynamics

Station Keeping

Metoceancondition along the

route

• Dynamic Analyses• Fatigue Analyses

• Offpipe (static)• Abaqus (static)• Pipelay (static)

• Offpipe(dynamic reg.& irreg. wave)

• Pipelay(dynamic reg.& irreg. wave)

• FIPLA

Ramp Management

vs.Water Depth

• Fully integrated DP and Pipelay Analyses

Lay VesselOperability

• In-house software

• Metocean forecasting• Operation Wave Nowcasting

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DESIGN FOR INSTALLATION – ANALYSIS OUTCOME

Analysis results (Overbend region & Stinger Tip)

-60 -40 -20 0 20 40 60 80 100 120

-25

-20

-15

-10

-5

0

5

10 Tenstop = 329 Tons

clr = 15.25 cm out = 28.50 deg

WD = -124 m Sagmax = 0.1238 %Tensbottom = 245 Tons

Dout = 44.0 in (1.1168 m) wtsteel = 0.0246 m Dout conc = 1.3468 m wtconc+cc = 0.115 m Wair = 19.8708 kN/m Wsub = 4.5609 kN/m

R10 - 0.2525 %

X Coord [m]

Y C

oord

[m]

R19 R18 R17 R16 R15 R14 R13 R12 R11 R10 R09 R08 R07 R06 R05 T030

0.1

0.2

0.3

R10 = 0.2525 %

Ben

ding

Stra

in [%

]


5000

10000 R10 = -9616 kNm

Stip = -2920 kNm

Rol

ler M

omen

t [kN

m]


200

400

600 R7 = 428 kN( 44 Tons )

Roller ID

Rol

ler R

eact

ion

[kN

]SEMAC1 - Wheatstone Project - OD = 44.0 in - WTsteel = 24.6 mm - WTconc = 110 mm

Moment

Strain

Pipe Configuration

Reactions

23


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DESIGN FOR INSTALLATION – LARGE CAPACITY EQUIPMENT

A&R/SUBSEA DEPLOYMENT SYSTEM WITH HIGHER CAPACITY Fabrication: feasibility up to dia 180mm, MBL 2500mT, length 3800 m Testing: availability of test facilities up to 2500 t Alternative solutions (use of multiple steel wires system) move problems

from the fabrication/testing of the steel wire to the inspection/discardcriteria

DESIGN CRITERIA Applicable standards for offshore A&R/Subsea deployment

winches/steel wire Safety factor definition criteria in Normal/Emergency Operation Wire Rope Fatigue Life design Criteria Test Requirements: break testing and test facilities available

MAINTENANCE/INSPECTION CRITERIA Maintenance of subsea ropes: lubrications (type of lubricants,

application methods, regulations) Monitoring/inspection during operation: method and criteria

(visual inspection, NDE, cut back and test, cycles data logging and fatigue monitoring )

Discard criteria: definition, methodology and regulation

25


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26

Accidental Flooding Scenarios failure modes: Excessive Bending Moment/Strain combined with

Point Load Force at stinger tip (mainly Deep Water scenarios);

Excessive Bending Moment/Strain at TDP region (mainly Shallow Water scenarios)

Defective through thickness girth weld Leaking valve on special items

Development ofexcessive bendingmoment/strain at thesagbend occurs dueto residual lay tensionreduction.

Stinger tip region is notcritical for the pipelineintegrity.

Stinger Tip

Sagbend

SHALLOW

Stinger tip region is criticalfor the pipeline integrity dueto development of excessivebending moment/straincombined with a point loadforce.

Development of excessivebending moment/strain atsagbend is limited.

Stinger Tip

Sagbend

DEEP Accidental Flooding Scenarios shall take

into account: Distinguish Deep vs. shallow water scenarios; Distinguish Trunkline vs. flowline (different

pipe flooding time and evolution); Contingency measures, if any, and lay vessel

structural integrity more than pipe integrity; Accidental flooding is generally driven by the

lay equipment and vessel integrity; Vessel equipment includes a smart wet buckle

detection system.

Pipe S and J Laying, Water Flooding during Installation

DESIGN FOR INSTALLATION – INCIDENTAL FLOODING


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DESIGN FOR INSTALLATION – AFT, SPECIAL EQUIPMENT

Parameters on a large and complex project55000 hp => 1000 hp100 M€ => 10 M€3600 psi => 36 psiRTO 72 h => 72 sRTO = Ready To Operate

• Principles / ApplicationUse a market available pipeline isolation tool for reducing flooding risk when laying in deepwater.

• ObjectivesDrastically reduce the need for a compression station at land, which is needed for pipeline recovery operations in case of pipeline rupture during laying.Compression station cost reduction.Reduce time to recover a pipeline damage situation, because only the last part of the pipeline need to be deflooded.

27


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DESIGN FOR INSTALLATION – IAU, SPECIAL EQUIPEMET

Buckle Risk area

TECHNOLOGY COMPARISON

Radio (RF), Pressure Wave (AC)Pros Fast Good Range

Hi‐Repeatability Hi‐RepeatibilityOn board noise proof Simple technology

Cons Accuracy AccuracyRange On board noise influenceComplex technology

Reduce risk in case of mechanical BD failure and retrieval. Reduce time for corrective actions.

Remote Buckle Detection

• Principles / ApplicationInjecting a signal (radio, pressure wave) into a waveguide (pipeline) face-end, each geometrical anomaly reflect part of the signal depending on its characteristics.

• ObjectivesA system which can provide a certified Buckle Measure up to the end of the stinger and capable to detect obstructions up to about 4 Km.

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Tensile stress-strain test

EXTERNAL

0180360

INTERNALHoop

Obtained curves from simulation

Compressive stress-strain

test

A sample

B sample

Sample location

EXTERNAL

360

C sample

D sample

180INTERNAL

Comparison: Test vs

numerical

Line Pipe Manufacturing

Issues (JC vs. UO)

Plate

“O”ing die

“U” ing

die

FINITE ELEMENT MODELING

Bauschinger effects included indesign criteria equation by afab(see DNV OS-F101)

WHERE (across thickness) and WHEN (plate, pipe, beforeor after coating) to characterise the compression capacityof the line pipe steel afab

DESIGN FOR INSTALLATION – MANUFACTURING VERY THICK LP

30


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Ovality and Collapse Resistance vs. Expansion/Compression Strain

UOE / UO / UOC COLD FORMINGPRESSURE vs. OVALITY

-7.00E+07

-6.00E+07

-5.00E+07

-4.00E+07

-3.00E+07

-2.00E+07

-1.00E+07

0.00E+000.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

Ovality [%]

Exte

rnal

Pre

sure

[Pa]

UO

UOE (E=0.4%)

UOE (E=1.3%)

UOC (C=0.5%)

UOC (C=1.0%)

DESIGN FOR INSTALLATION - COLLAPSE CAPACITY vs FAB

31

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Combined External Pressure and Bending (Baushinger Effect)

X65 OD=24" t=31.8mm - NUMERICAL ANALYSES (ABAQUS)

0.0E+00

5.0E+05

1.0E+06

1.5E+06

2.0E+06

2.5E+06

3.0E+06

3.5E+06

4.0E+06

4.5E+06

-2.0%-1.8%-1.6%-1.4%-1.2%-1.0%-0.8%-0.6%-0.4%-0.2%0.0%

MINIMUM COMPRESSIVE LONGITUDINAL STRAIN (%)

BEN

DIN

G M

OM

ENT

(Nm

)

t=31.8mm; fo=1%; X65, WD=2150m; Afab=1.00

t=31.8mm; fo=1%; X65, WD=2150m; Afab=0.90

t=31.8mm; fo=1%; X65, WD=2150m; Afab=0.85

Maximum or Limit Bending Moment

DESIGN FOR INSTALLATION – BENDING CAPACITY vs FAB

32

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Combined External Pressure and Bending

X65 OD=24" t=31.8mm - NUMERICAL ANALYSES (ABAQUS)

0.0E+00

1.0E+06

2.0E+06

3.0E+06

4.0E+06

5.0E+06

6.0E+06

-6.0%-5.5%-5.0%-4.5%-4.0%-3.5%-3.0%-2.5%-2.0%-1.5%-1.0%-0.5%0.0%MINIMUM COMPRESSIVE LONGITUDINAL STRAIN (%)

BEN

DIN

G M

OM

ENT

(Nm

)

Pure Bending, fo=1%, water depth=0mPressure + Bending, fo=1%, water depth=500mPressure + Bending, fo=1%, water depth=1000mPressure + Bending, fo=1%, water depth=1500mPressure + Bending, fo=1%, water depth=2150mMaximum or Limit Bending Moment

33

DESIGN FOR INSTALLATION – NUMERICAL LAB FOR STRENGTH C.

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34

FLOW ASSURANCE


DESIGN

OCEAN ENGINEERING



PIPELINE INTEGRITY

MANAGEMENT

MATERIALS & WELDING


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DESIGN FOR OPERATION – LIMIT STATES

35

The relevant failure modes and limit states for offshorepipeline in operation are the following:

Pressure Containment Capacity due to internal overpressure duringoperation and in field pressure tests;

Shear Running Fracture due to internal pressure; Collapse due to external pressure in case of pipeline depressurization; Buckle Propagation due to the external pressure in case of buckle

initiation and pipeline depressurization; Local Buckling due to internal and/or external pressure and bending due

to bottom roughness or lateral buckling in case of pipeline depressurizationand high pressure and temperature conditions.

Stress-Strain Capacity of defective girth welds during operation (it isnormal practice to say that an export pipeline has to withstand appliedtensile stress - strain up to yielding - 0.5%.

Fatigue damage of the girth welds due to environmental loads in operation(at free spans) and pressure and temperature fluctuations (oligocyclic).


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• Differential Pressure (Internal and/or External)• Steel Axial Force• Bending Moment

Pipeline strength and deformation capacity aims to quantify the maximumloads and the associated deformation the pipeline can taken when subjectto:

Dimensionless Curvature

Dim

ensi

onle

ss M

omen

t

Dim

ensi

onle

ss M

omen

t

Dimensionless Curvature

High D/t Ratio

Low D/t Ratio

Limit Bending Moment Capacity (LBMC)Curvature at Limit Bending Moment (CLBM)Lost of Capacity due to Strain Localization (LCSL)

Empty Pipe

Pipe Under Design Pressure

Limit Bending Moment Capacity (LBMC)Curvature at Limit Bending Moment (CLBM)

PIPELINE CAPACITY UNDER COMBINED LOADS

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HOTPIPE 2 - EXPERIMENTAL TESTS - PIPE SPECIMEN NO. 3BENDING MOMENT VS. CURVATURE RELATIONSHIP

0.00E+00

1.00E+05

2.00E+05

3.00E+05

4.00E+05

5.00E+05

6.00E+05

7.00E+05

8.00E+05

9.00E+05

1.00E+06

1.10E+06

1.20E+06

1.30E+06

0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400 0.450AVERAGE CURVATURE (1/m)

BEN

DIN

G M

OM

ENT

(Nm

)

T3 Pipe specimen t = 16.2 mm, , fo =0.0%, SMYS = 480 MPa, Mean D FE Mesh, Mid Section,

T3 Pipe specimen t = 16.2 mm, , fo =0.0%, SMYS = 480 MPa, Mean D FE Mesh, Mid Section, Triggering Force

Specimen 3 - Experimental Test

PIPE BENDING MOMENT CAPACITYFEM ANALYSIS vs. LABORATORY TESTS RESULTS

ABAQUS FE Models have been developed to evaluate the strength and deformation capacity of pipes subjected to combined loads

(int/ext pressure, axial force and bending)


37


saipemCORRODED PIPES

COLLAPSE

PIPELINE BENDING ON S-LAY STINGER

BUCKLE ARRESTOR DESIGN

SPECIAL COMPONENTS FEM ANALYSIS

POST-PROCESSING

“PIPEONE” PRE- and POST-PROCESSOR


LOCAL BUCKLING UNDER INTERNAL/EXTERNAL

PRESSURE, AXIAL LOAD AND BENDING

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For given defect acceptance,allowable stresses and strains

For given load condition,allowable defect size

The need of safely withstandingbending load effects (axial load effectsare minor) both during installation andin operation (including hoop loadeffects).

The strength capacity of girth weldsthreatened by weld defects must besuitably analysed to establish:

ECA - MINIMUM STRENGTH CAPACITY REQUIREMENTS

Pipe

Girth Weld

Defect

DEFECTS ACCEPTANCE

CRITERIA

PROJECT SPECIFICATIONS(CTOD-R CURVE)

STRAIN (4.0%)CAPACITY

NEEDED FORSPECIFIC/LOAD

SCENARIOS

Contractor Contractor to meetto meet

CompanyCompanyAsk ContractorAsk Contractor

PROJECT REQUIREMENTS

Who ECAs???

DESIGN FOR OPERATION – GIRTH WELD STRENGTH CAPACITY

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The relevant load condition for offshore pipeline in operationare the following:

Operational conditions i.e. design pressure and min and max designtemperature;

External pressure during shut – down; Sea bottom roughness giving rise to the formation of free span; Environmental loads (surface waves and marine currents) in the shallow

water section; High pressure and high temperature conditions giving rise to the

development of lateral buckling; Geohazards particularly plastic flows and turbidity currents.

DESIGN FOR OPERATION – EXTERNAL LOAD CONDITIONS

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Bottom Roughness and Free Span Analysis

SEABOTTOM PROFILE54400 56400 58400 60400 62400 64400 66400

KP (m)

-550

-500

-450

-400

-350

-300

-250

Wat

er D

epth

, m

Seabed morphology indicatesthe optimum route alignment

Sea bed preparation works(berms) by gravel dumping

Steep deep depression

Seabed morphology indicatesthe optimum route alignment

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

-70

-60

-50

-40

-30

-20

-10

99100 99200 99300 99400 99500 99600 99700 99800 99900 100000 100100

Am

plitu

de (

-)

WD

(m)

KP (m)

Cross Flow Vibration Mode - F = 0.370

0

0.2

0.4

0.6

0.8

1

1.2

-70

-60

-50

-40

-30

-20

-10

99100 99200 99300 99400 99500 99600 99700 99800 99900 100000 100100

Fatig

ue U

sage

Fac

tor (

-)

WD

(m)

KP (m)

Cross Flow Total DamageFatigue Damage

Cross-Flow Modal Analysis

Bottom Roughness Analysis

DESIGN FOR OPERATION – BOTTOM ROUGHNESS

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In-Service Buckling due to HP/HT Conditions

0 .0 0 0 0 0

0 .0 0 0 2 0

0 .0 0 0 4 0

0 .0 0 0 6 0

0 .0 0 0 8 0

0 .0 0 1 0 0

0 .0 0 1 2 0

0 .0 0 1 4 0

0 .0 0 1 6 0

0 .0 0 1 8 0

0 .0 0 2 0 0

0 .0 0 2 2 0

0 .0 0 2 4 0

0 .0 0 2 6 0

0 .51 .52 .53 .54 .55 .56 .57 .58 .59 .51 0 .51 1 .51 2 .51 3 .51 4 .51 5 .51 6 .51 7 .51 8 .51 9 .52 0 .5

K P

R = 6 2 0 m

R = 8 7 0 m

2 7 0 0 m

2 0 8 0 m

1 7 4 0 m

1 9 4 0 m

C ro s s in g

G F CH T C

V 1 0

V 9

V 8V 7

V 6

V 5V 4

V 3

V 2

V 1

2 1 7 0 m

2 1 1 0 m

1 9 3 0 m

2 0 3 0 m

1 8 2 0 m

C ro s s in g C ro s s in g

V1V2V3V4V5V6V7V8V9V10

-70

-65

-60

-55

-50

-45

-40

-35

-30

71500 71550 71600 71650 71700 71750 71800 71850 71900 71950 72000 72050 72100 72150 72200KP (m)

Y (m

)

-0.20

-0.10

0.00

0.10

0.20

0.30

0.40

0.50

Embe

dmen

t (m

)

CC 90 As-Laid

CC 90 Deformed

CC 65 As-Laid

CC 65 Deformed

Embedment Inner

Embedment Outer

CURVE 5

LIGHTENING

DESIGN FOR OPERATION – HIGH TEMPERATURE HIGH PRESSURE

49


saipem330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 3520

0.2

0.4

0.6

0.8

1

KP (km )

Loc

al B

uck

ling

Un

ity C

hec

330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352-200

-100

0

100

200

KP (km )

Y-c

oo

rdin

ate

(m

)

As -La id Hydrotes t Operating_Condi tions

330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 3520

2000

4000

6000

8000

KP (km )

Ho

rizo

nta

l B

OP

Cur

vatu

reR

ad

ius

(m)

As -Laid Hydrotes t Operating_Condi tions Sm oothed Pipe l ine Configuration

330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352-95

-90

-85

-80

-75

-70

KP (km )

Z-c

oord

inat

e (

m)

As -La id Hydrotes t Operating_Condi tions Vertica l Seabed Profi le Vertica l Seabed Profi le - Modi fied

As -La id Hydrotes t Operating Condi tions

All the relevant pipe parameters are plotted as a function of the KP

330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352-0.02

0

0.02

0.04

0.06

0.08

KP (km )

Max

imu

m L

ongi

tudi

nal

Tota

l Str

ain

(%)

330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352-1000

-500

0

500

1000

1500

KP (km )La

tera

l B

en

din

g M

om

en

t (k

N

Horizontal Pipeline Configuration

Pipeline Curvatures

Vertical Pipeline Configuration

Longitudinal Strains / Stresses

Lateral and Vertical Bending Moments

Lateral Buckling Unity Check (DNV-OS-F101)

IN-SERVICE BUCKLING ANALYSIS USING 3-D SEA BOTTOM PROFILE

INTEGRITY ASSESSMENT IN OPERATION (DESIGN PHASE)

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Detailed ABAQUS FEM analyses to:- Investigate the puncture resistance of the pipe

shell due to the impact- Quantify the pipe shell behavior due to the

interaction with a dragged anchor duringhooking

- Quantify the global-local behavior of the pipebeam hooked by large dragged anchors

Pipeline Structural Integrity against Ship Traffic Related Threats Anchor Hooking

NORD STREAM PROJECT: Dragged Anchor AnalysisLONGITUDINAL STRAIN VS. ANCHOR FORCE RELATIONSHIP

FINLAND OD = 1.21482m WT= 30.9mm

-4.0%

-2.0%

0.0%

2.0%

4.0%

6.0%

8.0%

0 1000 2000 3000 4000 5000 6000 7000 8000

ANCHOR FORCE (kN)

MA

XIM

UM

& M

INIM

UM

LO

NG

ITU

DIN

AL

STR

AIN

LC5 FREE FEED-IN Pi=19.5MPa - EF=-7.000kN - 0.25/0.30

LC6 FREE FEED-IN Pi=19.5MPa - EF=-7.000kN - 0.50/0.90

LC7 10000 m Pi=19.5MPa - EF=-7.000kN - 0.25/0.30

DESIGN FOR OPERATION – IMPACT FROM HUMAN ACTIVITY

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55

FLOW ASSURANCE


DESIGN

OCEAN ENGINEERING



PIPELINE INTEGRITY

MANAGEMENT

MATERIALS & WELDING


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SOLID CORROSION RESISTANT ALLOY PIPE• DUPLEX OR SUPERDUPLEX

CS OUTER PIPE & CRA INNER PIPE• MECHANICAL BOND OR LINED PIPE

• METALLURGICAL BOND OR CLADDED PIPE

MATERIAL - ALTERNATIVE PIPE CONCEPTS

Weld Overlay Seal Weld

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MATERIAL - PERFORMANCES OF NEW CONCEPTS

• DUPLEX OR SUPERDUPLEX EXPENSIVE NOT SUITABLE FOR EXTENSIVE APPLICATION AND SENSITIVE TO THERMAL DE-RATING

• CLADDED PIPE AND LINED PIPE ARE LESS EXPENSIVE BUT…

• SOME TECHNOLOGICAL GAPS TO BE ADDRESSED BY SUPPLIERS, CONTRACTORS AND OPERATORS JOINT EFFORTS

• APPLICATION FOR HT/HP PIP SYSTEM IN A SNAKED LAY CONFIGURATION PERFORMED BUT EXTREME COMPLEX AND AT THE TECHNOLOGY LIMIT

GIRTH WELD

GIRTH WELD

LINER DISBONDMENT

FATIGUE RESISTANCE

CRACKS

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MATERIAL – TRADITIONAL, NEW PIPE CONCEPT FOR REEL LAY

Reel-lay is the process where rigid pipes are:1. Prefabricated as long strings and stacked in dedicated onshore bases;2. Spooled onto a storage reel on-board the reel-lay vessel, yielding the steel;3. Transported onto the offshore field;4. Unwounded, straightened and laid by a dedicated system on-board the vessel.

New Competitors (Heerema, EMAS) are entering in the market with an alternative process different from the conventional one by:

2. Spooling the pipe onto a storage reel placed on-board a dedicated barge/supply vessel;

3. Transporting it onto the offshore field and lifting it by the reel-lay vessel crane.

1 2 3 4

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MATERIAL – REEL LAY TECHNOLOGY

Conventional reeling applications (since '70 up to 2k): More than 6000 km of steel pipelines laid especially

in GoM and North Sea Mainly flowlines (up to 16") in water depths that

were increasing through the years In the '90 also more complex products (e.g. PiP, SCR,

thick insulation, …) were laid in deep water (up to1000 m)by reeling

The best in class vessel of those years, the "Apache",is still operative (re-hulled in 2010) and owned byTechnip

65

Late reeling applications (2000-2010): More than 14000 km of pipelines laid worldwide Contractors invested both in new vessels and in onshore

spoolbases to warrant presence in "golden triangle" Complex field development projects in deep water (up to

3000 m) increases their market share To face new demanding market needs Technip delivered

the best in class multi-lay vessel Deep Blue (lay tension 550 tons)


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Thanks!

THANKS

68

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