1
MSc in Subsea Engineering
EG55F6 Risers Systems and Hydrodynamics
Overview of Riser EngineeringDr Patrick O’BrienHonorary Professor of Engineering, University of Aberdeen & Group Director, MCS Kenny
MSc in Subsea Engineering
Presentation Overview
1. General Concepts & Field Layout
2. Riser System Types
3. Overview of Fundamentals of Riser Engineering
4. Riser Design Considerations
EG55F6 Risers Systems and Hydrodynamics
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MSc in Subsea Engineering
Key Messages
Dry tree vs wet tree: Tensioned vs Compliant
Riser TypesypTTRs, Flexibles, SCRs, Hybrids
Riser FundamentalsLarge displacement, effective tension, equations of motion, time vsfrequency domain
Riser Design ConsiderationsVessel motionsTouchdown response and buckling
EG55F6 Risers Systems and Hydrodynamics
Touchdown response and bucklingFlexible pipe design issues and failure modesSCR design issues: touchdown and top connection flex/stress jointInternal flow regime and insulationCross-section impact on global motionsCoupled vessel-mooring-riser response
MSc in Subsea Engineering
1 G l C t & Fi ld L t1. General Concepts & Field Layout
• Dry Tree vs Wet Tree• Tensioned vs Compliant
EG55F6 Risers Systems and Hydrodynamics
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MSc in Subsea Engineering
RESERVOIR CONDITIONS
ENVIRONMENTAL
Riser System Selection
FIELD LAYOUT
SURFACE UNIT
PRODUCTION SCHEME
CONDITIONS
EG55F6 Risers Systems and Hydrodynamics
RISERSYSTEM
MSc in Subsea Engineering
System Architecture: Girassol Subsea
EG55F6 Risers Systems and Hydrodynamics
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MSc in Subsea Engineering
Boomvang Nansen Fields
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
Two Main Riser Types“Dry Tree” riser“Wet Tree” riser
Preliminaries:(Christmas) Tree ~ “manifold” type structure
EG55F6 Risers Systems and Hydrodynamics
( ) ypPoint at which reservoir fluid iscontrolled“Head” of the well
Tree at seabed ~ “Wet” TreeTree at sea surface ~ “Dry” Tree
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MSc in Subsea Engineering
Feasibility of Dry or Wet Tree...
“A riser should be vertical below wellhead (or Tree)”Tree)
to allow equipment to be transmitted through the well
If Dry tree riser...Riser must be vertical (from surface to seabed)Cannot be connected directly to moving vessel
EG55F6 Risers Systems and Hydrodynamics
Cannot be connected directly to moving vesselIf Wet tree riser...
No need to be vertical (from surface to seabed)Can connect directly to vessel (Slack in Riser)
MSc in Subsea Engineering
Dry vs Wet Tree Fundamentals
How to cope with motions of vessel (Dry)Riser Supported Vertically by buoyancy canspp y y y yRiser connected to vessel by Tensioners
Tensioners (like springs) extend and compressRiser top response decoupled from vessel motions
Vessel Heaves, riser doesn’t
How to cope with motions of vessel (Wet)
EG55F6 Risers Systems and Hydrodynamics
( )Riser connected directly to vesselEnough slack/compliancy built into riser
e.g. use of Wave shape configuration
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MSc in Subsea Engineering
Offshore Production Facility Types
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
Floating Production Vessel Types
FPSO
SemiD d ft
Mini TLP
EG55F6 Risers Systems and Hydrodynamics
Deep draft
SPAR
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MSc in Subsea Engineering
Independence Hub Semi
World’s deepest risers…2,438m
SCRs – 7 Initial- 9 Future
Umbilicals
EG55F6 Risers Systems and Hydrodynamics
Umbilicals –STU
MSc in Subsea Engineering
Technology Limits: Water Depth
Deepest Semisubmersible (Independence Hub approx 2,440m)( p pp )(Nakika 1,920m)
Deepest TLP (Magnolia approx 1,433m)
EG55F6 Risers Systems and Hydrodynamics
Deepest Spar (Devil’s Tower approx 1,707m)
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MSc in Subsea Engineering
2 Ri S t T2. Riser System Types
• Top Tensioned Risers (TTRs)• Flexible Risers• Steel Catenary Risers (SCRs)• Hybrid Steel Flexible Risers
EG55F6 Risers Systems and Hydrodynamics
• Hybrid Steel-Flexible Risers
MSc in Subsea Engineering
SPAR Top Tensioned Risers
EG55F6 Risers Systems and Hydrodynamics
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MSc in Subsea Engineering
SPAR Risers - Detail
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
Riser Top Tensioners (TLP)
EG55F6 Risers Systems and Hydrodynamics
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MSc in Subsea Engineering
Individual Riser Tensioners
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
Top Tension Riser Design
EG55F6 Risers Systems and Hydrodynamics
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MSc in Subsea Engineering
Dry vs Wet Tree Design
• Must have dual independent barrier between uncontrolled reservoir fluid and environment
Outer Annulus
Inner Annulus
13 3/8 “ Outer Casing
9 5/8” Inner Casing
5 ½” Production Tubing
– I.e. below wellhead
• Dry Tree– Single or Dual Casing Riser
• (from Seabed to Surface)
EG55F6 Risers Systems and Hydrodynamics
• Wet Tree– No need (below wellhead = below seabed)
MSc in Subsea Engineering
TTR Riser Design Issues
What is the wall thickness of casings?Withstand stresses (hoop axial bending )Withstand stresses (hoop, axial, bending,..)Extreme, fatigue, VIV loading
How many cans/tensioners required to support the risers?
EG55F6 Risers Systems and Hydrodynamics
Tapered sections (reinforcements at seabed and vessel interfaces)
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MSc in Subsea Engineering
Flexible Risers
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
Flexible Pipe Cross SectionCarcass (Stainless Steel)
– External Pressure Resistance
Carcass Profile:
Example : Rough-bore Pipe (with Carcass)
Internal Sheath (Polymer)– Internal Fluid Containment Barrier
Pressure Armor (Carbon Steel)– Hoop Load Resistance
Armor Profile:
EG55F6 Risers Systems and Hydrodynamics
Tensile Armor (Carbon Steel)– Tensile Load Resistance
External Sheath (Polymer)– External Fluid Barrier
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MSc in Subsea Engineering
FREE HANGING LAZY WAVE STEEP WAVE
Flexible Riser Configurations
EG55F6 Risers Systems and Hydrodynamics
PLIANT WAVE® STEEP S LAZY S
MSc in Subsea Engineering
Bend Stiffeners
FunctionPrevents over-bending Bend
Stiffener
Provides moment transition between flexible and rigid end connection
Design ConsiderationsPolyurethane fatigue and creep
Non-linear material propertiesSteel collar for load transfer
Steep Wave
EG55F6 Risers Systems and Hydrodynamics
Steel collar for load transferInterface arrangement
e.g. I-tubes, porch,Manufacturing tolerances
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MSc in Subsea Engineering
Buoyancy Devices
TypesDistributed – lazy wave and steep wave configurations
Configuration achieved by buoyancy modulesManufacturers include
Trelleborg CRP LtdFlotechEmerson Cuming
Concentrated – lazy S and steep S configurationsConfiguration achieved by tether buoy
EG55F6 Risers Systems and Hydrodynamics
g y yManufacturers include
Trelleborg CRP Ltd
MSc in Subsea Engineering
Distributed BuoyancyDistributed
Steep-waveLazy wave Lazy PliantSteepLazy-wavePliant waveFloatation attached to result in desired riser configurationBuoyancy Supplied by discrete modules
Lazy Wave
Pliant Wave®
Steep Wave
EG55F6 Risers Systems and Hydrodynamics
Clamps required for buoyancy module to make connection to pipe
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MSc in Subsea Engineering
Distributed Buoyancy
Design considerations– Usually syntactic foam– Net buoyancy requirement
output from configuration design– Clamping
EG55F6 Risers Systems and Hydrodynamics
gModule slippage can alter
configuration– Gradual loss of buoyancy over time– Clashing
MSc in Subsea Engineering
Distributed Buoyancy
Buoyancy Module2 half shellsHeld in place by clampHalf shells strapped together over clampProfiled to avoid overbending of riser
EG55F6 Risers Systems and Hydrodynamics
overbending of riser
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MSc in Subsea Engineering
Distributed Buoyancy Issues• Numerical modeling of modules -
discrete or smeared• Accounting for parameters that reduce g p
buoyancy:– Water absorption– Initial elastic compression– Creep– Marine growth– Manufacturing tolerances
• Review of design requirements for system with lost modules currently
Courtesy of Trelleborg CRP Ltd.
EG55F6 Risers Systems and Hydrodynamics
system with lost modules - currently 10% in API RP 17B
• Guidance on module spacing
MSc in Subsea Engineering
Concentrated BuoyancyConcentrated buoyancy
Steep-SLazy-Sy S
Design considerationsUsually pressurized steel tanksBuoyancy requirement
ensure taut in all internal fluid conditionsCompartmentalized buoyancy tanks
Steep-S Lazy-S
EG55F6 Risers Systems and Hydrodynamics
RedundancyTether hold-down arrangementGutter to prevent interference
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MSc in Subsea Engineering
Subsea Arch
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
Subsea Arch
EG55F6 Risers Systems and Hydrodynamics
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MSc in Subsea Engineering
Subsea Arches - Key Issues
• Redundancy for mid-water arches with buoyancy tanks in case of fl d d t k/ t tflooded tank/compartment– Depends on risk level i.e. production
(oil) versus water service over mid-water arch
– Too much redundancy can be prohibitive
– Tolerances– Arch Sizing – Installation issues
EG55F6 Risers Systems and Hydrodynamics
gCourtesy of Trelleborg CRP Ltd.
MSc in Subsea Engineering
Steel Catenary Risers
EG55F6 Risers Systems and Hydrodynamics
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MSc in Subsea Engineering
Steel Catenary Risers
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
Hybrid Riser Key Components
Flexible jumpers(dynamic bundles)
Buoyancy tank(air cans)
Taper joint (or hinge connection)
Riser bundle (integral/non integral)Core pipe
(tether)
EG55F6 Risers Systems and Hydrodynamics
Spools (jumpers)
Flexjoint (taper joint)
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MSc in Subsea Engineering
Hybrid Riser Towers – Tower Extremity Illustrations
Tower-Jumper Interface
Seabed Connection
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
Single Leg Hybrid Risers
Bend StiffenerFPSO
Single Pipe Riser
Bend StiffenerFPSO
FlexibleJumper
Rigid Jumper
50 mBuoyancy Tank (5.0m diax 25-30m long)
Riser Base Joint
EG55F6 Risers Systems and Hydrodynamics
Rigid Jumper
FlowlineSuction Pile
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MSc in Subsea Engineering
3 O i f F d t l f3. Overview of Fundamentals ofRiser Engineering
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
Beam Stressesy
x
∫= dAT σ
z
dxdMzVy =
E l B lli B
EG55F6 Risers Systems and Hydrodynamics
∫
∫−= dAyM z σAxial stresses much larger than shearstresses
Euler-Bernoulli Beam:
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MSc in Subsea Engineering
Effective Tension
Global EffectsDerive effective tension from apparent weightAdditional hydrodynamic and mechanical loads add to effective tensionBuckling is a function of effective compression (negative effective tension); not true wall compression
Internal Cross-Section EffectsWork with true wall tension and compute true wall
EG55F6 Risers Systems and Hydrodynamics
pstressStress criteria developed from true wall tension and other stressesVon Mises derived from true wall tension
MSc in Subsea Engineering
Riser Large Displacements
EG55F6 Risers Systems and Hydrodynamics
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MSc in Subsea Engineering
Convected Axes – Deformed Riser
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
RdKFdKdCdM =+=++
Final Matrix Equations of Motion
~rb~~~~~ −−−−
Mathematically, system of 2nd order linear differential equationsEquations are nonlinear as mass and stiffness matrices are functions of displacement. Nonlinear stiffness includes terms that are a function of stress (effective tension)Rigid body terms accounts for large displacement and rotation
EG55F6 Risers Systems and Hydrodynamics
Solve in Time Domain or Frequency Domain
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MSc in Subsea Engineering
Frequency Domain MethodDecompose into 2 equations:
dddDynamic:
Static:
~t
~t
~t
~t FdKdCdM =++
−−−
~rb
~c
~c dKFdK
−−+=
Note: M, C and K assumed time-invariantC t l h t i li it
EG55F6 Risers Systems and Hydrodynamics
Cannot apply where geometric nonlinearity significant in dynamicNote capacity for linearised dynamic aboutnonlinear static
MSc in Subsea Engineering
Frequency Domain Dynamics
~~
ti
~~t
ti
~~t Complexd,F:edd:eFF ωω
0000 −==
Substitute into dynamic equation
ti
~~t
ti
~~t edd:edid ωω ωω 0
20 −==
ti
~
ti
~eFed)KCiM( ωωωω 00
2 =++−
EG55F6 Risers Systems and Hydrodynamics
Solve directly for d0~
Solve matrix equation once for single frequency
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MSc in Subsea Engineering
Wave Spectrum Discretisation
Equal area discretisationArea =Sη(ω n )dω = 1
2 a2n
ωn
Sη(ω )
ω, radians/second
Area =Sη(ω n )dω = 12 a2nArea =Sη(ω n )dω = 12 a2n
ωnωn
Sη(ω )Sη(ω )
ω, radians/second
EG55F6 Risers Systems and Hydrodynamics
dω
,
dωdω
,
η ω φ( ) cos( )t a k y ti ni
N
n i= − +=∑
1
MSc in Subsea Engineering
Fatigue Calculations: Time Domain vs Frequency Domain
Spectrum discretised into finite number of harmonics
Time DomainTime DomainRandom wave synthesised by superposition with random phasesGenerate time-history of wave loading and vessel motionsRun time domain analysis for 3 hour storm (54,000 timesteps)Statistical analysis of output timetraces to calculate fatigue damage
Frequency DomainSolve equations of motion once for each wave spectrum harmonic (50 harmonics)
EG55F6 Risers Systems and Hydrodynamics
harmonic (50 harmonics)Generate response spectrum directlyCalculate fatigue life from properties of response spectrum
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MSc in Subsea Engineering
Fatigue CalculationsFrom To 0.0024 0.1533 2.1821 10.9055 29.4055 32.5839 14.5441 7.4283 2.2937 0.3821 0.1017 0.0173 100
0 1 0.0024 0.1389 0.4586 1.1013 1.7016 0.5055 0.0934 0.0000 0.0092 0.0000 0.0000 0.0000 4.011044881 2 0.0000 0.0140 1.5456 4.9933 12.2997 8.7117 1.6113 0.3840 0.0958 0.0151 0.0048 0.0000 29.67522962 3 0.0000 0.0003 0.1732 3.9070 8.5255 11.1960 4.1127 0.9179 0.1215 0.0270 0.0000 0.0000 28.98116823 4 0.0000 0.0000 0.0048 0.8611 4.8037 6.5943 3.4991 1.9210 0.3316 0.0441 0.0541 0.0075 18.121234 5 0.0000 0.0000 0.0000 0.0376 1.6510 3.0600 2.4005 1.5853 0.5127 0.0376 0.0072 0.0000 9.291797665 6 0.0000 0.0000 0.0000 0.0051 0.3539 1.5647 1.3607 1.1369 0.4860 0.0192 0.0096 0.0096 4.945700486 7 0.0000 0.0000 0.0000 0.0000 0.0657 0.6708 0.7023 0.6509 0.3919 0.0575 0.0014 0.0000 2.54044251
Hs (m) Totals
7 8 0.0000 0.0000 0.0000 0.0000 0.0044 0.2492 0.4908 0.2940 0.0982 0.1109 0.0202 0.0000 1.267654468 9 0.0000 0.0000 0.0000 0.0000 0.0000 0.0318 0.2187 0.2361 0.0910 0.0394 0.0007 0.0000 0.617741989 10 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0489 0.1817 0.0554 0.0082 0.0007 0.0000 0.2950103
10 11 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0055 0.0825 0.0421 0.0072 0.0007 0.0000 0.1379224511 12 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0003 0.0284 0.0284 0.0055 0.0007 0.0000 0.0634237912 13 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0078 0.0165 0.0041 0.0006 0.0001 0.028977413 14 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0016 0.0081 0.0027 0.0004 0.0000 0.0129229614 15 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0002 0.0034 0.0018 0.0003 0.0000 0.0057222415 16 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0013 0.0010 0.0002 0.0000 0.0024983516 17 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0004 0.0006 0.0001 0.0000 0.0010712117 18 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0001 0.0003 0.0001 0.0000 0.00044149
From 0 2 4 6 8 10 12 14 16 18 20 22 FromTo 2 4 6 8 10 12 14 16 18 20 22 24 ToMean 1 3 5 7 9 11 13 15 17 19 21 23 Mean
Tp (s)
Wave Scatter Diagram
225.1270.1
315.1
m-6
.84
s-0
m-6
.63
s-0
m-5
.60
s-0
-5.9
1s-
0.3
6s-
45
10
s-4
5
27
s-4
5
7s-
45
3s-
90
s-9
0
s-9
0
-90
35
35 5 5
1.00E-08
1.00E-07
1.00E-06
1.00E-05
Damage
Full-3D Bending
-6.00E+00--5.00E+00
-7.00E+00--6.00E+00
-8.00E+00--7.00E+00
EG55F6 Risers Systems and Hydrodynamics
Frequency Domain- Solve for each seastate- Fatigue damage from spectrum
of response
0.145.1
90.1135.1
180.1225.1
2.3
8m
1.7
8m
1.8
9m
1.8
9m
-2
.20
m-7
1.8
5m
-6.
1.8
9m
-6.2
1.6
1m
-7.3
2.1
5m
-8.1
3
1.8
7m
-6.8
1
1.9
4m
-8.2
3s
2.2
4m
-8.3
8s-
1.3
3m
-9.0
0s-
1
1.7
8m
-10
.14
s-1
3
2.7
9m
-9.2
7s-
13
1.8
2m
-10
.08
s-1
35
1.9
0m
-11
.61
s-1
80
1.6
1m
-11
.17
s-1
80
2.3
5m
-10
.62
s-1
80
1.9
1m
-11
.19
s-1
80
3.5
2m
-12
.31
s-1
80
2.1
7m
-10
.30
s-1
80
1.7
5m
-9.6
1s-
18
0
1.6
8m
-10
.62
s-2
25
1.6
5m
-9.7
5s-
22
5
2.1
6m
-10
.83
s-2
25
2.3
9m
-10
.19
s-2
25
3.5
6m
-11
.90
s-2
25
2.6
2m
-11
.79
s-2
25
3.6
1m
-11
.05
s-2
25
2.7
3m
-10
.67
s-2
25
Location (Wire.Cnr)
Loadcase (Hs1, Tp1, Dir1)
Fatigue Damagearound Cross-Section
MSc in Subsea Engineering
Frequency Domain Results (1)
0.004
0.006
0.008
0.01
Curvature Stand
ard De
viation (1/m
)
EG55F6 Risers Systems and Hydrodynamics
0
0.002
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
Loadcase No
Curvature at Fatigue Hotpsot
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MSc in Subsea Engineering
Frequency Domain Results (2)
0.001
0.0015
0.002
0.0025
0.003
0.0035
Curvature Standard Deviatio
n (1/m
)
EG55F6 Risers Systems and Hydrodynamics
0
0.0005
620 621 622 623 624 625 626 627 628
Distance along riser (m)
Bend Stiffener Region
MSc in Subsea Engineering
4 Ri D i C id ti4. Riser Design Considerations
• Vessel Motions• Touchdown Response & Buckling• Flexible Pipe Design & Failure Modes• Internal Flow Regime and Insulation
EG55F6 Risers Systems and Hydrodynamics
• Internal Flow Regime and Insulation• Cross-section impact on global motions• Coupled vessel-mooring-riser response
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MSc in Subsea Engineering
Riser Host Vessel Characteristics
1. Host Vessel vs Water Depth2. Host Vessel 6 DoF Motions3. Vessel Motions & Environmental Forces4. Mean Loads & Excursions5. High Frequency Forces & Excursions6. Low Frequency Motions & Excursions7. Host Vessel Motion Data for Riser Design8. Coupled vs Uncoupled Motion Analysis9 H t V l M ti Ch t i ti
EG55F6 Risers Systems and Hydrodynamics
9. Host Vessel Motion Characteristics10. Host Motions Induced Riser Fatigue
MSc in Subsea Engineering
Types of Mooring Systems
EG55F6 Risers Systems and Hydrodynamics
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MSc in Subsea Engineering
Vessel Motions & Environmental Forces
• Mean Excursions– Drag dependent
•Wind, current
• High Frequency Motions– Heave, Roll & Pitch (buoyancy dominated)– Surge, Sway & Yaw (drag, skin friction
dominated)– Not influenced by mooring stiffness or risers
• Low Frequency Motions– Highly mooring stiffness influenced
EG55F6 Risers Systems and Hydrodynamics
g y g– Interaction of waves of different frequencies in
an irregular sea.– Drag dominated
MSc in Subsea Engineering
Moored Vessel Motions
API MaxMean
HF (peak)
Mean LF (sig/max)HF (sig/max)
‘Initial’ Offset for Riser Simulations
EG55F6 Risers Systems and Hydrodynamics
Vessel Excursion
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MSc in Subsea Engineering
Vessel 6 DOF Motions
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
Mean Loads & ExcursionsConstant loads
Wind & current (6 DOFs, although often only 2 DOFs)
Considered in riser design as static essel e c rsionsConsidered in riser design as static vessel excursions
Wind & Current
Static Excursion
EG55F6 Risers Systems and Hydrodynamics
Free Hanging Catenary
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MSc in Subsea Engineering
High Frequency Forces & Excursions
1st order, wave frequency component
Compiled from:Model tests
1.2
1.4
deg/
ft)
Model testsRadiation/diffraction
programsGenerally imposed in riser
design as motion RAOs (6 DOFs)
0.0
0.2
0.4
0.6
0.8
1.0
0 4 8 12 16 20 24 28
Period (sec)
Dis
plac
emen
t RA
O (f
t/ft)
& R
otat
iona
l RA
O (
Heave Surge Pitch
60
90
120
150
180
(deg
rees
)
Ph
Head Sea (incident on Bow)
EG55F6 Risers Systems and Hydrodynamics
-180
-150
-120
-90
-60
-30
0
30
4 8 12 16 20 24 28
Period (sec)
Phas
e A
mps
wrt
to W
ave
Cre
st (
Heave Surge Pitch
PhaseLead
PhaseLag
MSc in Subsea Engineering
Low Frequency Motions & Excursions
2nd order wave and wind components (mainly wave)Can be significant loads for severe stormsLow damping at these long periods from mooring
Compiled from:Model TestsRadiation/Diffraction analysis
Often imposed in riser design as sinusoidal response superimposed on HF motions
EG55F6 Risers Systems and Hydrodynamics
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MSc in Subsea Engineering
Vessel Motion Characteristics
WF LF OtherTLP moderate low ringingg gSpar low moderate Hull VIVSemi moderate moderate Hihg heave motionsFPSO high high High heave motions
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
SCR Riser to Host Connection
Flex Joints– Lower bending to riser porches– Larger configurations limitsLarger configurations limits– HT elastomer performance challenges– More expensive than stress joints
Stress Joints– Current limit: 10” ID, approx 65 ft long
(depends on machining and transportation capability)R i d l th i l f hi h ti
EG55F6 Risers Systems and Hydrodynamics
– Required length is long for high motion vessels
– High bending applied to riser porch
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MSc in Subsea Engineering
Flexible Riser to Host ConnectionBend StiffenersBend Restrictor
EG55F6 Risers Systems and Hydrodynamics
Steep WaveSteep Wave
Bend Stiffener
MSc in Subsea Engineering
Riser Buckling at Touchdown
THE OIL COMPANYPROPOSAL PREPARED FOR
A i ti
DATE
EG55F6 Risers Systems and Hydrodynamics
Animation
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MSc in Subsea Engineering
Riser Hang-off Location on FPSO
Buckling– Heave & pitch induced heave
dominated
Sensitivity of Vertical Motion to Riser Hangoff Positioning
2
2.2Hangoff 0m Forward of COMHangoff 50m Forward of COMHangoff 100m Forward of COMdominated.
– TLP/Spar Vessel: small heave implies riser compression generally not an issue
FPSO: Heave is significant– Pitch induced heave depends
on distance from COM
– Bow mounted turret is most 0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
RA
O o
f Ver
tical
Mot
ion
(m/m
) Hangoff 150m Forward of COMHangoff 200m Forward of COM
EG55F6 Risers Systems and Hydrodynamics
severe 00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Period of Response (s)
MSc in Subsea Engineering
Analysis of Post-Buckling Behaviour
Beam Element Equations– Use small deformation beam bending equations
DATE
– Modelling of geometric nonlinearity required to account for post buckling behaviour
– Convected Co-ordinates to account for Geometric Nonlinearity under large deformations and rotations
Solution once Pcr is not exceeded for each element
Element lengths sho ld be s fficientl small
EG55F6 Risers Systems and Hydrodynamics
– Element lengths should be sufficiently small
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MSc in Subsea Engineering
Riser Hang-off Motions
1.5
-0.5
0
0.5
1
50 55 60 65 70 75 80 85 90
Non
Dim
ensi
onal
Par
amet
erve
Incr
easi
ng, N
egat
ive
Dec
reas
ing )
EG55F6 Risers Systems and Hydrodynamics
-1.5
-1
Time (s)
N (
Posi
tiv
VelocityAccelerationCurvature
MSc in Subsea Engineering
Non-Dimensional Buckling Parameter
PROPOSAL PREPARED FOR
dragalTer DCd
gmV ....2
min ρ=
THE OIL COMPANY
02.10.02002
Drag Force
= .Cd.ρ.Ddrag.V2
Drag Force
= .Cd.ρ.Ddrag.V2
EG55F6 Risers Systems and Hydrodynamics
Gravitational Force
Fd = m.g
Gravitational Force
Fd = m.g
Non-Dimensional Buckling Parameter: πb = Vhangoff / Vterminal
36
MSc in Subsea Engineering
Curvature vs Non-Dimensional Parameter
3.50
4.00
4.50
0.50
1.00
1.50
2.00
2.50
3.00
Max
Han
goff
Velo
city
/Pip
eTe
rmin
al V
eloc
ity
4.5" Water Injeciton Near6" Production Near 4.5" Water Injection Far
EG55F6 Risers Systems and Hydrodynamics
0.000 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
Maximum Resultant Curvature (1/m)
6" Production Far
πb>1 implies high touchdown curvature
MSc in Subsea Engineering
Tension vs Non-Dimensional Parameter
4.00
4.50
1.00
1.50
2.00
2.50
3.00
3.50
Max
Han
goff
Velo
city
/Pi
pe T
erm
inal
Vel
ocity
4.5" Water Injection Near
EG55F6 Risers Systems and Hydrodynamics
0.00
0.50
-100 -80 -60 -40 -20 0 20 40 60 80 100
Minimum Effective Tension (kN)
4.5 Water Injection Near6" Production Near4.5" Water Injection Far6" Production Far
Onset of buckling for πb>1
37
MSc in Subsea EngineeringFlexible Riser Design Issues
Alternative ConfigurationsS
ConfigurationWave
ConfigurationFree-HangingConfiguration
Free Hanging Catenary
Lazy WaveLazy-S
LazySWave
EG55F6 Risers Systems and Hydrodynamics
Pliant Wave®(Tethered)
Steep-S Steep Wave
Steep
MSc in Subsea Engineering
Flexible Pipe Cross SectionCarcass (Stainless Steel)
– External Pressure Resistance
Carcass Profile:
Example : Rough-bore Pipe (with Carcass)
Internal Sheath (Polymer)– Internal Fluid Containment Barrier
Pressure Armor (Carbon Steel)– Hoop Load Resistance
Armor Profile:
EG55F6 Risers Systems and Hydrodynamics
Tensile Armor (Carbon Steel)– Tensile Load Resistance
External Sheath (Polymer)– External Fluid Barrier
38
MSc in Subsea Engineering
Current Design Limitation: Water Depth vs ID
Water Depth vs. IDFlexible Risers: Design Limits
1000
1500
2000
2500
Wat
er D
epth
( m
)
Field Data
Qualification
EG55F6 Risers Systems and Hydrodynamics
0
500
0 2 4 6 8 10 12 14 16 18
Riser / Flowline ID (in)
MSc in Subsea Engineering
Design Pressure vs ID
15 000
DP psi3" DRAPS
Pressure vs. IDFlexible Risers: Design Limits
5 000
6 000
7 000
8 000
9 000
10 000
11 000
12 000
13 000
14 000
4" Veslefrikk
9" Aasgard A/B
Terra Nova
MagnusT ll W ll t
Gyrfalcon Wellstream
(sweet API17J P x ID = 90 000
P x ID = 67 000
EG55F6 Risers Systems and Hydrodynamics
0
1 000
2 000
3 000
4 000
5 000
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20ID in
16.6" Aasgard B
Troll CSOGulfaks
Vigdis
Statfjord B
Aasgard B
Troll Wellstream
39
MSc in Subsea Engineering
Example Configurations - Animation
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
Flexible Pipe Bending - Hysteresis
Stick-Slip BendingTensile Armour initially sticks on reverse bendingSlip is inline with and transverse to lay-directionHysteretic fatigue stress
Regular Stress0
50
100
150
ress
(M
Pa)
EG55F6 Risers Systems and Hydrodynamics
Regular Stress Cycle
-150
-100
-50
-0.1 -0.05 0 0.05 0.1
Pipe Dynamic-Curvature (rad/m)
Wir
e S
tr
40
MSc in Subsea Engineering
Hysteresis Curve Cycles
150
-50
0
50
100
Wir
e S
tres
s (M
Pa)
EG55F6 Risers Systems and Hydrodynamics
-150
-100
-0.1 -0.05 0 0.05 0.1
Pipe Dynamic-Curvature (rad/m)
MSc in Subsea Engineering
Tensile Armour Wire Stress
Components of stressTension inducedTension-induced
Axial symmetric model
Wire bending stressLoxodrome model
Lay angle assumed constrainedWire bends about both principal axes
EG55F6 Risers Systems and Hydrodynamics
Friction-induced stressNonlinear hysteretic responseThe main hurdle to globally integrated stress analysis
41
MSc in Subsea Engineering
Wire Equations of Equilibrium
0,1211 =+ tott
dsd σσ
Tangential 2
Method of SolutionI t l t d t i i t l li i l t
0,2211 =− diffnt σκσ
0,3211 =+− tottt σκσ
Surface Normal
Transverse
13
EG55F6 Risers Systems and Hydrodynamics
Incremental curvature determines incremental non-slip axial stressIncremental non-slip axial stress determines incremental tangential shear, normal interface and tranverse shear stressesCheck Coulomb law and gradually relax stresses while retaining equilibriumWire curvatures from loxidromic / geodesic equations
MSc in Subsea Engineering
Friction-Induced StressMCS Structural Model for Friction – Regular Loading
Pipe Bending Curvature
1.0E-02
1.5E-02
/m)
Wire Stress
40
60
80
)
-1.5E-02
-1.0E-02
-5.0E-03
0.0E+00
5.0E-03
0 5 10 15 20 25 30
Time
Cur
vatu
re (r
ad/
-80
-60
-40
-20
0
20
0 5 10 15 20 25 30
Time
Stre
ss (M
Pa)
Hysteresis Loop
40
60
80
a)
EG55F6 Risers Systems and Hydrodynamics
-80
-60
-40
-20
0
20
-1.5E-02 -1.0E-02 -5.0E-03 0.0E+00 5.0E-03 1.0E-02 1.5E-02
Pipe Curvature (rad/m)
Stre
ss (M
Pa
42
MSc in Subsea Engineering
Friction-Induced StressMCS Structural Model for Friction – Irregular Loading
Wire Stress
6080
100
)
Pipe Bending Curvature
0 010.0150.02
0.025
d/s)
-80-60-40-20
02040
0 10 20 30 40 50 60
Time
Stre
ss (M
Pa)
-0.025-0.02
-0.015-0.01
-0.0050
0.0050.01
0 10 20 30 40 50 60
Time (s)
Cur
vatu
re (r
ad
Hysteresis Loop
6080
100
)
EG55F6 Risers Systems and Hydrodynamics
-80-60-40-20
02040
-0.02 -0.02 -0.01 -0.01 0.00 0.01 0.01 0.02 0.02
Pipe Curvature (rad/m)
Stre
ss (M
Pa)
MSc in Subsea Engineering
3D (out-of-plane) Irregular Seas3D Pipe Bending in Irregular SeasHs = 2m, Tp = 13s, 15deg off-bow
Global Tension (left) and Curvature (right) Responses
1 65E+06
1.70E+06
0.006
0.008
1 45E 06
1.50E+06
1.55E+06
1.60E+06
1.65E+06
Tens
ion
(N)
-0.002
0
0.002
0.004
Cur
vatu
re (r
ad/m
)
EG55F6 Risers Systems and Hydrodynamics
1.40E+06
1.45E+06
15 35 55 75 95 115Time (s)
-0.006
-0.004
Tension Local-y Pipe Curvature Local-z Pipe Curvature
43
MSc in Subsea Engineering
3D (out-of-plane) Irregular Seas3D Pipe Bending in Irregular SeasHs = 2m, Tp = 13s, 15deg off-bow
Armour Total Stress at 8 Equally Spaced Positions on the Cross Section800E+06
550E+06
600E+06
650E+06
700E+06
750E+06
Stre
ss (P
a)
EG55F6 Risers Systems and Hydrodynamics
450E+06
500E+06
15 35 55 75 95 115Time (s)
0deg 45deg 90deg 135deg 180deg 225deg 270deg 315deg
MSc in Subsea Engineering
Flexible Pipe Failure Modes
Outer SheathHole, Tear, Rupture, Crack
Outer Sheath Damage
Ingress of Sea Water
Repair Clips on riser Section
ROV installation of riser repair clamp. Outer sheath was damaged during riser deployment
EG55F6 Risers Systems and Hydrodynamics
44
MSc in Subsea Engineering
Flexible Pipe Failure Modes
End FittingInternal Pressure Sheath Pull-outInternal Pressure Sheath Pull outTensile armour Pull-outOuter Sheath Pull-outVent Valve Blockage / LeakageFailure of Sealing SystemCrack or Rupture of Tensile
EG55F6 Risers Systems and Hydrodynamics
ArmourStructural Failure of End Fittingbody or Flange From OMAE2004-51431, outer
sheath failure due to blocked riser vent valve.
MSc in Subsea Engineering
Flexible Pipe Failure Modes
Tensile Armour LayersMultiple Wire RuptureMultiple Wire RuptureBirdcaging or ClusteringKinkingIndividual Wire Rupture
EG55F6 Risers Systems and Hydrodynamics
45
MSc in Subsea Engineering
Flexible Pipe Failure Modes
Carcass Hole Crevice Pitting or ThinningHole, Crevice, Pitting or ThinningUnlocking DeformationCollapse or OvalisationCircumferentialCracking / Wear Fatigue
Carcass Profile:
EG55F6 Risers Systems and Hydrodynamics
PiggingMulti-Layer PVDF
MSc in Subsea Engineering
SCR Design Issues
SCR = Steel Catenary Riser
EG55F6 Risers Systems and Hydrodynamics
46
MSc in Subsea Engineering
Example Systems
• Typical for many GOM SCRs
• FavourableFavourable performance with TLPs
• Spar low motions favour SCRs
EG55F6 Risers Systems and Hydrodynamics
AnimationAnimation
MSc in Subsea Engineering
SCR Design Process Flowchart
Fundamental Stages:
Design
• Strength (Pipe & FJ) • WF Fatigue • VIV Fatigue • Installation Analysis • Interference
CP D i
Assumptions
Design Basis i) WD ii) SCR Diameter
Design
– Design
– Procurement, Construction, Testing
– Installation
• CP Design • Fracture Mechanics
• Design Sensitivities • As-Built Design Analysis • Design Verification
Procurement, Construct & Testing
• Procurement • Delivery & End Match • Fatigue Testing • Welding & Spooling
Pipe
F/J
S - N
SCFs
Pipe Weights
)iii) Fluids iv) Waves v) Currents vi) Soil vii) TLP Motions
Reeled
EG55F6 Risers Systems and Hydrodynamics
– Operation Installation
Operations
As-installed ROV-surveyed SCR condition
Installation
Installation Fatigue
47
MSc in Subsea Engineering
SCR Global Configuration
• Steel Catenary Riser (SCR)Simple catenary shape effectively– Simple catenary shape – effectively an extension of a seabed pipeline
– Close to 200 SCRs installed or planned
– Used for most export risers in GoM
EG55F6 Risers Systems and Hydrodynamics
– More recently widely employed for production service to semis, Spars, FPSOs and fixed structures.
MSc in Subsea Engineering
Key SCR Design Issues
1. Wall-Thickness Design
2 Host Vessel Layout and tie-in2. Host Vessel Layout and tie in
3. Interference Design
4. Strength Design
5. VIV Design
6. Fatigue Design & Qualification
EG55F6 Risers Systems and Hydrodynamics
7. Riser Hangoff (Porch) Design
8. Fracture Mechanics: UT Defect Criteria
9. Installation Engineering
48
MSc in Subsea Engineering
Components & Critical Design Areas
Typical hang-off receptacle with flex joint
Taper Stress joint (TSJ)
EG55F6 Risers Systems and Hydrodynamics
VIV StrakesSeabed Trenching
MSc in Subsea EngineeringSCR Component Design
TSJs and FlexJointsTSJs
Limits curvature without overstress
Transmits bending moment into vessel hang-off
Titanium or Steel Construction
FlexJointsCombination of steel and elastomer layers
Flexjoint connected to hull via riser porch
Bellows may be required
(Courtesy of RTI Energy Services)
EG55F6 Risers Systems and Hydrodynamics
Bellows may be required
Spool connects flexjoint to hull piping
Reduces bending moment at the riser vessel hang-off
49
MSc in Subsea Engineering
VIV Suppression: Strakes/Fairings
Mitigation of VIV – Under long term and extreme currents
1 Strakes
(Courtesy of CRP)
EG55F6 Risers Systems and Hydrodynamics
1. Strakes– Typically polyurethane, fibreglass or plastic
2. Fairings– Typically fibreglass or plastic
MSc in Subsea Engineering
Typical SCR Stress Outputs
015
0017
50s)
20-inch Gas Export 15 deg HO10-inch Production 14 deg HO8-inch Production 12 deg HO
8-inch Production 14 deg HO Typical Effective Tension Profile
0 2500 5000 7500 10000 12500 15000Curvilinear Distance along the set SCR (feet)
025
050
075
010
0012
50E
ffect
ive
Tens
ion
(kip
s
2530
35is
es S
tres
s (k
si)
20-inch Gas Export 15 deg HO10-inch Production 14 deg HO8-inch Production 12 deg HO
8-inch Production 14 deg HO
Touchdown
EG55F6 Risers Systems and Hydrodynamics
0 2500 5000 7500 10000 12500 15000Curvilinear Distance along the set SCR (feet)
510
1520
API
RP
2RD
von
Mi
Typical API RP 2RD Stress ProfileHang-Off
50
MSc in Subsea Engineering
Fatigue Life Along SCR Length
100,000,000
1,000,000,000
10,000
100,000
1,000,000
10,000,000
, ,
Fatig
ue L
ife (y
ears
)
DirliksRayleigh
Hang-Off
EG55F6 Risers Systems and Hydrodynamics
100
1,000
10,000
0 500 1000 1500 2000 2500 3000 3500 4000 4500
Distance from Top of SCR (ft)
Hang OffSeabed
Touchdown
MSc in Subsea Engineering
SCR Touchdown Fatigue
Behaviour at SCR touchdown point (TDP) key p ( ) ydesign driver
Fatigue
TDP response source of
EG55F6 Risers Systems and Hydrodynamics
design uncertaintySoil propertiesLimitations of soil models
51
MSc in Subsea Engineering
SCR-Soil Interaction Modelling
Non-linear soil modelling now included in Flexcom
STRIDE JIP Soil suction model using soil force-deflection curve
EG55F6 Risers Systems and Hydrodynamics
MSc in Subsea Engineering
CP Anodes, Inhibitors & Coatings
1. External Corrosion Protection• Determine required anode mass and spacing• Not be desirable along SCRs• Not be desirable along SCRs
2. External Corrosion Coatings• FBE corrosion protection mechanically bonds pipe
materials to external insulation (PE, PP)• Typically TLPE for TDP • Often TSA for straked sections
3. Corrosion Inhibitors
EG55F6 Risers Systems and Hydrodynamics
• Corrosion protection/inhibition within SCR.
52
MSc in Subsea Engineering
Insulation / Heating Technology State of the Art
Passive approach using the thermal inertia of materials added around the element to insulate. Important properties of the materials are:
Thermal conductivity
Heat capacity
Density
Active approach by adding some thermal energy to maintain the element at a given temperature. Energy can be brought by:
Hot water
EG55F6 Risers Systems and Hydrodynamics
ElectricityDirect heatingSkin effectInduction
Mixed approach combining the two technical solutions described above
MSc in Subsea Engineering
Riser Concepts – Flow Assurance1. SCR / Riser Tower
With or without wet insulation
2 Pipe-in-pipe (PIP) SCR2. Pipe-in-pipe (PIP) SCRImproved Flow AssuranceSignificantly heavier
3. Flexible Pipe w/ insulationProven design & track record
4. Integrated Production Bundle (IPB)Integrated Gas Lift, heating and services
EG55F6 Risers Systems and Hydrodynamics
g , gEvolving technology – based on flexible pipe
5. Integrated Production Umbilical (IPU)Integrated Gas Lift, heating and servicesEvolving technology – based on SCR
53
MSc in Subsea Engineering
Riser Concepts (continued)6. Single Leg Hybrid Riser (SLHR) – Single Pipe
With or without wet insulationCombines steel and flexible pipe
7. Single Leg Hybrid Riser (SLHR) – Pipe-in-PipeDry insulation
8. Hybrid Bundle Riser (SLHR)Wet insulated bundle
EG55F6 Risers Systems and Hydrodynamics
9. Top Tensioned Riser (TTR)
MSc in Subsea Engineering
Integrated Production Bundle (1)External Plastic Sheath
Thermal Insulation
Tubes forHot Water or/and Gas Lift
EG55F6 Risers Systems and Hydrodynamics
Flexible Riser Structure
Technip Patent
54
MSc in Subsea Engineering
Integrated Production Bundle (2)
EG55F6 Risers Systems and Hydrodynamics
Courtesy Technip
MSc in Subsea Engineering
Riser Solutions – Flow Assurance
EG55F6 Risers Systems and Hydrodynamics
55
MSc in Subsea Engineering
Integrating Riser Design & Flow Assurance
Key items of integrationInsulation and its impact on riser drag-to-weight ratioRiser slugging and its impact on riser dynamics and ultimatelyRiser slugging and its impact on riser dynamics and ultimately fatigue damage
Deep Water Steel Catenary Riser ExampleHow does riser shape influence slugging?How does slugging affect fatigue life?
Methodology of InvestigationPerform slugging analysis with multiphase transient flow assurance software
EG55F6 Risers Systems and Hydrodynamics
Link flow assurance output with riser dynamics software and compute response
Key FindingsSlugging can have significant fatigue damage and depends of type of slugging and inclination of flowline into riser
MSc in Subsea Engineering
Flow Assurance & Riser Dynamics
Riser Insulation:Increases outside diameter of pipe at lower density levels
Drag-to-weight RatioDrag is a destabilising horizontal force and is proportional to riser diameterWeight (in water) is a vertically downward stabilising forceDrag-to-weight (DTW) ratio is a measure of hydrodynamic stabilityRiser values vary from 2m2/tonf to 8 m2/tonf
EG55F6 Risers Systems and Hydrodynamics
Insulation increases the DTW valueLimit on amounts of insulation for catenary risers
Effective Tension is important for buoyant and top tensioned risers
56
MSc in Subsea Engineering
Flow Assurance & Riser Dynamics
Riser Slugging:Impact of riser shape on sluggingImpact of riser shape on sluggingImpact of riser slugging on riser fatigue
Force terms from:changes in pressure and densitycentripetal due to slug velocity along curved riser
EG55F6 Risers Systems and Hydrodynamics
risercoriolis due to fluid motion in the moving riser frame of reference
MSc in Subsea Engineering
Slugging CharacterisationWADO - Slugging Example - PPL Data
10" Flowline, Downslope, 20000 BPD, 90% Water Cut, 150 Sm3/Sm3Slug Length Profiles (4x)
800
300
400
500
600
700
1.00 hours1.25 hours1.50 hours1.75 hours2.00 hours2.25 hours2.50 hours2.75 hours3.00 hours
EG55F6 Risers Systems and Hydrodynamics
0
100
200
15000 16000 17000 18000 19000 20000 21000 22000 23000 24000 25000 26000 27000 28000
Distance (feet)
Time, length and location of slugs
57
MSc in Subsea Engineering
Riser Model Discretisation
15 mSect 1
15 mSect 2
15 mSect 3
SLUG
Riser discretisation for slug force computation
WADO - SCR Touchdown Point Fatigue Enhancements10" Catenary Riser Profile
-1250
-1000
-750
-500
-250
0
TOPSIDES
RISER_1ARISER_1C
RISER_1B
RISER_2RISER_2C
RISER_2B
RISER_3
RISER_3
RISER_3
RISER_3
RISER_2D
RISER_1D
Riser section identification
Force terms computed from fluid pressure and density changes centripetal and
EG55F6 Risers Systems and Hydrodynamics
-2500
-2250
-2000
-1750
-1500
0 250 500 750 1000 1250 1500 1750 2000 2250
Distance from FPSO, m
changes, centripetal and coriolis forces due to slug / riser motions
MSc in Subsea Engineering
Coupled vs Uncoupled Motions•Coupled Motion Analysis (Hydrodynamic coupling)
•(QTFs, wave forces RAOs, current & wind force coefficients, radiation damping & added matrices)•Required if inertia, damping, stiffness of risers & mooring significantly affectRequired if inertia, damping, stiffness of risers & mooring significantly affect response of host facility
EG55F6 Risers Systems and Hydrodynamics
•Uncoupled•RAOs, offsets, sinusoidal drift•Full vessel time history (Spar generally)
Prescribed Motions
58
MSc in Subsea Engineering
Installation Vessels - SCRs
J-Lay
EG55F6 Risers Systems and Hydrodynamics
Reel Lay
MSc in Subsea EngineeringInstallation, Schedule, Cost Drivers
Steel Riser and FlowlineInstallationS-lay
used up to moderately deep water, modified stinger for very deep waterlimit is curvature induced at stinger
J-laydeep to ultra-deep water riser installation, typically expensive option
Reel-layFaster than J-Lay with more controlled shop (2G - horiz) instead of offshore (5G) welding
EG55F6 Risers Systems and Hydrodynamics
More complex weld testing and fracture mechanics– Large diameter may imply high reeling strains – max strain and low cycle
fatigue challenges– Requires nearby spool base to be economical (WoA challenge)
59
MSc in Subsea EngineeringRiser & Flowline System SelectionImpact on Cost and Schedule
Flexible Pipe– Tradeoff = procurement cost vs. installation cost
Steel Flowlines and SCRs– Often lowest procurement cost in deepwater– Deepwater pipelay vessel : J-Lay or reeled lay typical for deepwater
applications, S-Lay for shallow-moderate depth
Riser Towers– Typically most expensive riser installation option
B dl i t ll ti t i ll b t t
EG55F6 Risers Systems and Hydrodynamics
– Bundle installation typically by tow-out– SLHR installation may be pipelay vessel or MODU installation
MSc in Subsea EngineeringInstallation Challenges and VesselCapacity
● Installation ChallengesUltra-deepwater high tension loadsLarge diameterLarge diameterPositioning for TDP & clashing during transferRigging/handling of pull-in/abandonmentWeather fatigue during installationVessel on-site vs. abandonment & recovery (A&R)
● Installation Vessel Capacities:Max. Pipe
L TLay tension
V lC
EG55F6 Risers Systems and Hydrodynamics
60S2,500SolitaireAllseas32J1160S-7000Saipem60 (S), 18 (R)S, R1200HerculesGlobal
28R, J1697Deep BlueTechnip30J2800BalderHeerema
pSize (in)
Lay Typey(kips)
VesselCompany
Based on Reported Tension Capacities (2003)
60
MSc in Subsea Engineering
Procurement & Installation Costs
Procurement Costs– Line Pipe or flexible pipe– Corrosion Protection coatingsCorrosion Protection coatings– Insulation Coating (riser/flowline), concrete coating (flowline)– J-lay Collars– Ancillary devices (Flexjoints, strakes, anodes, buoys, clamps, bases, bend
stiffeners/restrictors, buoyancy modules/tanks, pipe supports or mudmats)Installation Cost– Mobilization– Prefabrication (onboard or at spool base)– Offshore Installation = f (vessel, inst. method)
EG55F6 Risers Systems and Hydrodynamics
– Lifting and handing over to receptacle– Tie-in & hydrotest– Demobilization
Miscellaneous – Engineering, Inspection, Contingency
MSc in Subsea Engineering
Issues Considered
Riser TypesTTRs, Flexibles, SCRs, Hybrids
Ri F d t lRiser FundamentalsTension / Bending, Effective TensionLarge displacementsTime Domain vs Frequency Domain
Extreme vs FatigueVessel motions
Touchdown bucklingTh l id ti
EG55F6 Risers Systems and Hydrodynamics
Thermal considerationsRiser Design and Flow AssuranceDrag-to-Weight RatioInstallation
61
MSc in Subsea Engineering
Key Messages
Dry tree vs wet tree: Tensioned vs Compliant
Riser TypesypTTRs, Flexibles, SCRs, Hybrids
Riser FundamentalsLarge displacement, effective tension, equations of motion, time vsfrequency domain
Riser Design ConsiderationsVessel motionsTouchdown response and buckling
EG55F6 Risers Systems and Hydrodynamics
Touchdown response and bucklingFlexible pipe design issues and failure modesSCR design issues: touchdown and top connection flex/stress jointInternal flow regime and insulationCross-section impact on global motionsCoupled vessel-mooring-riser response
MSc in Subsea Engineering
The End
Any Questions?
EG55F6 Risers Systems and Hydrodynamics