module 3.5 - flowlines & risers

7/27/2019 Module 3.5 - Flowlines & Risers

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Subsea Systems Integration Course

Subsea Flowlines and Risers

Course Module – Subsea Flowlines and RisersModule 3.5





Module Objective

• Objective:

Review the various designs and installation techniques available for

transporting hydrocarbons from the well to the host platform. Identify the

drivers for the flowline and riser designs. Explain the impact of different

design decisions on the subsea system.

• At the end of this session you will be able to:Identify the flowline and risers options

Define the design drivers and critical decisions for

flowline system selection

Recognize the ramification of the critical component

selection





Primary Function – To Transmit Product From “A” To “B”

Production – well to host

Production – well to subsea infrastructure

Design Drivers

Operational / Flow Assurance Strategy

Installation Strategy / Vessel Availability

Lift gas, injection water (flow in opposite direction)

Anticipated Loads (Internal, External, Installation)


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•Required Cooldown Time

•Required Arrival Temp.

•Wax Strategy•Erosion Potential

•Asphaltenes

•Hydrate Strategy

•Internal Corrosion

•External Corrosion

Thermal Retention

•Bare, Polymer Insulation,

Burial, Pipe-in-Pipe,

Bundled Pipe

Functional Architecture

•Single Lines, Looped or

Dual Line System, Riser

Type, Termination Type

Materials

•Carbon Steel, CRA, Liners,

Clad Pipe

Flow Assurance Drivers

Decisions



Subsea Flowlines and Risers Thermal Retention

Bare Pipe

Pipe-in-Pipe

•low CAPEX

•very installable

•no heat retention

•may exclude someinstallation methods

•highest installation

loads (top tension)

•may not be possible

to repair

•may require onshore

fabrication facilities

Corrosion Coating

Only

Polymer Insulated •must be qualified forwaterdepth

•weak link is the field

joints

•may limit installation

vessels

Low Density Insulation

Outer Pipe

Bulkheads and/or

Waterstops

BundlesInsulated Pipe•limited deepwater

burial systems

•may not work in all

soils

•requires

consolidation time

•not proven for

deepwater •requires onshore

infrastructure

•may not be possible

to repair

•long tows have a

history of problems

Insulated or Flooded Annulus

Service and Control

Lines

Outer Pipe

Flexibles•application limits for high

temp, high pressure,

chemical exposure

•prefabricated

Buried Pipe



Subsea Flowlines and Risers Thermal Retention

Electrical Heating

Methods

• Pipe-in-Pipe (skin effect)

• Single Pipe (return cable in close proximity)

• Bundled Single Pipe (return cable within the

bundle)

Applications

• Continuous – always providing heating

• Ever Ready – can be “turned on” at any time• Ready – hardware included subsea to allow

intervention spread to supply electrical power

“Current” Limitations

• Dry Terminations Only – there does not exist a

submerged, load bearing electrical isolation joint for

the riser

• Limited Access to Intervention Spread (EH Ready)

– Only one intervention spread exists, CAPEX costis high

EH Intervention





$-

$100,000

$200,000

$300,000

$400,000

$500,000

$600,000

$700,000

2.0 12.0 22.0 32.0 42.0 52.0 62.0 72.0 82.0

Length (miles)

C

o s t p e r i n c h - d i a - m i l e

Pipe-in-Pipe

Insulated

Bare 43%

83%

Thermal Retention

Cost Comparison of Flowline Systems




Subsea Flowlines and Risers Functional

Architecture

Components of the Flowline System

• Riser

• Terminations

• Flowline

Termination with Flowline Sled Preparation for Riser Hang-off





Single Leg

Hybrid Risers

or Towers

J-Tube Risers

Clamped Risers

Near Vertical Risers (NVR)

& Steel Steepwave Risers (SSR)

Steel Catenary Riser (SCR)

Top TensionLazy Wave

Functional

Architecture




Subsea Flowlines and Risers Functional

Architecture

Hubs – Flowpath Extension

Termination – Distribute Bending Stress and End Load

Mudmat – Resist Settlement

and MovementInstrumentation – Monitor

Flowpath Condition

Platform – ROV Parking

Hubs – Future Connections and

Injection Points

Valves – Isolation or Flow Direction

Installation AidsHinge – Reduce Installation Forces

Hook – Recovery, Rotation Resistance





Daisy-ChainFlowline

System

Functional

Architecture

Dual

Flowline

System

Single

Flowline

System

•piggable

•can produce through single line

during late life, in the event of

damage, or during unique

activities such as expansion•dual sided blowdown capable

for hydrates

•allows segregation of

production (high pressure/low

pressure, well testing, etc.)

•approx. 30% less CAPEX

•piggable

•can produce through single line

during late life, in the event of

damage, or during unique

activities such as expansion•allows greater/optimum

spacing of wells

•allows limited segregation of

production (high pressure/low

pressure, well testing, etc.)




Subsea Flowlines and RisersMaterialsOxygen

Carbon dioxide (“sweet”)

Bacteria

Hydrogen sulfide (“sour”) - can be ofbacterial origin

Acids (organic, inorganic) - can be ofbacterial origin

Low Alloy Carbon Steel (X-70 and less)

• non-corrosion resistant

Low Alloy Carbon Steel (high strength)

• hydrogen embrittlement

• welding Issues

• limited availabilityCRA Clad Carbon Steel

• welding Issues

• inspection Issues (NDE)

• manufacturing issues

• expensive, may be limited to critical areas

Solid CRA

• hydrogen embrittlement

• welding issues

• galvanic concerns with adjacent materials

Non-Metallic Linings

• field joints difficult

• may limit installation method

• bonding with pipe

Strategies

Use a corrosion allowanceRegular replacement

Coatings

Cathodic Protection Coating

Chemical protection

Maintenance, e.g. pigging

Use Corrosion Resistant Alloy (CRA)

Use Non-Metallic Material

Issues







Design Drivers










Installation Drivers

Decisions

•Vessel Availability and

Cost

•Potential Conflict of

Activities or Access

•Vessel Capabilities

Lay Methods

•S-lay, J-lay, Reeled, Towed

System Components•Risers, Flowline System

Field Access

•First Ends Sleds, Second

Ends Sleds, Fixed PlatformRisers, Floating Host Risers




Subsea Flowlines and RisersLay Method

Installation techniques – S-Lay

Wide range of pipe diameters

Multiple welding stations

Deepwater limited by weight of span

and collapse on the stinger

Limitations on what can be passed

through the stinger (valves, sleds, etc.)

Typical lay rate = 2-4 miles/day




Subsea Flowlines and RisersLay Method

Installation techniques – J-Lay

Wide range of pipe diameters

Limited number of welding stations

(typically one)

Lowest span weight, allowing

deepwater advantage

Not suited to piggyback lines, etc.


Double or Quad jointing of pipe

requires onshore fabrication facilities

Shallow water limitations





Lay Method

Installation techniques – Reel-Lay

Limitations on max. pipe size (~ 18”)

Reel capacity may be limited by

length or weight of pipe

Requires extensive onshore

fabrication facilities

May require multiple transits to re-

spool Can accommodate piggyback lines, etc

Suits internal plastic lining

Limitations on what can be passed

through the stinger (valves, sleds, etc.)

Not all pipe or insulation is “reelable”






Lay Method

Installation techniques – Towing

Continuous lengths limited (~ 4 miles)

Long tows and deepwater tows have

history of failures

Specialized onshore build site required

Pipe-in-pipe, piggybacks, etc, possible

Sleds incorporated as tow/trail heads

S b Fl li d Ri





System Components

J-Tube Risers

• Limited inspection capabilities (inside tube)

• J-tubes must be pre-installed

• Quick, cost effective installation

• Pull forces may be high

Clamped Risers

• Requires diving operations

• Riser is exposed to potential impact damage

S b Fl li d Ri





Single Leg Hybrid Risers or Towers

• Installation independent of the host

• Minor host loading

• Allows wells located close to the host

Near Vertical Risers• Allows well located close to the host

• Medium host loading

Steel Catenary Risers

• High host loading

• Inexpensive

• Not buoyancy dependent

• Well must be far from host

Lazy Wave Risers

• Medium host loading

• Wells must be far from host

System Components

S b Fl li d Ri





Field Access

Abandonment Cable

Laydown AreaLay Vessel

Installation Strategy must includeaccess to the field and should consider:

• conflicts between floating assets

• conflicts with mooring cables and abandonment cables

• station keeping capabilities proximity of floating assets

Subsea Flowlines and Risers Fi ld A




Subsea Flowlines and Risers Field Access

TowedReeledJ-layS-lay

Clear Accessrequired

Clear AccessRequired



SecondEnd at

Rig


Pull-in fromrig mounted

winch;seafloor sheave

required



required



required

First Endat Rig

With orwithout thehost; subsea

tie-in


Pull-in withhost mounted

winch/jack

Requires useof slack loop

Lay Past andSweep, Stalk

Riser

SecondEnd atHost

With orwithout thehost; subsea

tie-in

Pull-in withhost mountedwinch/jack,sheave onseafloor

If host is notpresent,

holdbackanchor

initiation

Pull from Host(or Vessel)

Bow-StringInitiation,

Stalk Riser;holdback

anchorinitiation

First Endat Host

HybridTopTension

SCR J-tubeClamped

Riser/Sled Lay Method

Difficult or

Rig/Host cannot be present

Only under

specific circumstancesUnmarked are

Unrestricted with

planning









Design Drivers










Loading Drivers Decisions

• Internal Pipe Loads

• External Pipe Loads

• Installation Loads

Pipe Design

• Maximum Pressure,

Operational Allowances,

Design Criteria

Environmental Conditions

• Route Selection,

Hydrostatic Collapse, Spans,

Riser Fatigue

Installation and

Operational Loads

• Selection of Design

Criteria, Vessel Limitations






Pipe DesignWall Thickness =

Operating Pressure Containment

+ Shut-In Tubing Pressure

+ Internal Corrosion Allowance

+ Internal Erosion Allowance

+ Mechanical Loss Allowance

+ On-Bottom Stability

+ Span Fatigue

+ Collapse Resistance

+ Thermal Buckling Resistance

Installation Early Life Mid Life Late Life

Early Life Mid Life Late Life








P r i m

a r y

I m p

a c t

Life of the Flowline System






Subsea Flowlines and Risersi




Subsea Flowlines and RisersEnvironment

Stability

Faults

Shallow Hazards

Slopes

Host

Well

Subsea Flowlines and RisersE i




Subsea Flowlines and RisersEnvironment

Axial Load

Current

Overbend Strain on Stinger

Touchdown Fatigue

Sagbend Strain

Construction Fatigue

Axial Load

Vortex Inducted VibrationVortex Inducted Vibration

Collapse and Propagation

Thermal GrowthCurrent Spans

Impact

Roller Impact Load





CAUTIONS





EXTREMELY ROBUST WILL LIKELY JUST

FAIL IN A NEW WAY





Too good to be true,

probably is too goodto be true.

Qualification is

critical.





Module Objective

• Objective:

Review the various designs and installation techniques available for

transporting hydrocarbons from the well to the host platform. Identify the

drivers for the flowline and riser designs. Explain the impact of differentdesign decisions on the subsea system.

• At the end of this session you will be able to:

Identify the flowline and risers options

Define the critical decisions for flowline system selection

Recognize the ramification of the critical component

selection

module 3.5 - flowlines & risers

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