SUT - Subsea Awareness Course - EW Feb 2012 Rev 1

Subsea Awareness CourseSociety for Underwater Technology

Vish Krishnamurthy – Senior Flexible Design Engineer - FDT

February 2012

Introduction

The aim of the presentation is:

To introduce rigid pipeline design and installation.

The course is high level and aims to present an overview of pipelines.

Please ask questions as we go!!!

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Contents

1. Pipeline Overview

Typical Pipeline Types

2. Pipeline Design

Design Process

3. Pipeline Installation

Methods of installation

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Three main topics

Comparison of Rigid Pipe Vs. Flexible

Advantages of Rigid Pipe:

3

Can sustain higher temperatures and pressures

Greater size range - up to 72” and higher pressure retaining

Generally cheaper to buy

For most applications cheaper (Maybe not the case for higher grade materials)

Generally used for longer lengths

Less susceptible to material degradation

1. Pipeline Overview - Rigid Pipeline Types

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Pipeline Types

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Basic Pipeline

Steel pipe (Generally carbon steel)

Corrosion coating on the outside

Corrosion allowance on the inside (additional wall thickness)

Most common type of pipeline in use subsea

May be coated with concrete to increase stability and impact protection

(Generally only 16” and upwards)

Pipeline Types

Insulated pipeline

Steel pipeline with corrosion protection and insulation coatings

Used when the product must be kept warm (e.g. wax or hydrate formation)

Called „wet insulation‟ as insulation is exposed to seawater

Minimum possible OHTC is approximately 1.5 - 4.0 W/m2.°K

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Pipeline Types

Lined pipes

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Used to protect the internal surface from corrosion.

Carbon steel pipeline.

Liner made of thermoplastic or CRA material (corrosion resistant alloy).

Plastic liners have successfully been used for water injection lines.

CRA steel alloys may be welded into the inside of the pipeline.

Pipeline Types

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Flowline (pressure retaining pipe) held and centralised in outer carrier pipe.

Gap filled with insulation.

More efficient than traditional „wet insulated‟ pipelines for high insulation

applications, high temperature or deep water.

Expensive, but possible OHTC of less than 1W/m2.°K.

Pipe-in-pipe

2. Pipeline Design

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Pipeline Design Overview

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Pipeline Design

Design Codes

Functional loads

Internal pressure

External pressure

Pressure and temperature-induced expansion

External (environmental) loads

On-bottom stability

On-bottom roughness

Spans

Protection

Installation loads

Pipeline Design Codes

Pipelines are designed using recognised standards or „design codes‟.

These design codes detail the requirements pipelines must meet.

Cover all areas of pipeline design (Corrosion, burst, installation etc…..)

Commonly used design codes are

ISO 13623 = BS EN 14161 ► PD 8010 (UK standard)

DNV Series, principally DNV OS-F101

API Series, principally API 1111

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Design Codes

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Pipeline Design

Flow Assurance

Pipeline Type

Linepipe Material & Coatings

Wall Thickness Selection

Pipeline Stability

Pipeline Expansion

Pipe Thermal Buckling

Pipeline Protection

Pipeline Design Flowchart

Flow Assurance

Flow Assurance

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Hydraulic flow calculations using preliminary production / test data.

To ensure that flow arrives at required.

Pressure

Temperature

Pipeline size ensures arrival pressure.

Pipeline insulation ensures arrival temperature.

Flow Assurance

Defines

Operating pressure

Operating temperature

Required pipeline diameter

Identifies need for any pipeline insulation

Pipeline Design utilises this Data

Flow assurance needs to consider practical aspects

Installation contractor capabilities

Available materials such as insulation materials

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Flow Assurance


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Pipeline Design

Flow Assurance

Pipeline Types



Pipeline Stability

Pipeline Expansion


Pipeline Protection

Linepipe

Most Common Types of Steel Pipeline

Seamless Pipe – drawn out of steel ingots

Best overall properties, but most expensive

Seam Welded Pipe – made from flat plate rolled and welded

Can be cheaper.

Limited range of diameters and wall thicknesses

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Seamless Linepipe

Piercer

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Linepipe

Seamless Linepipe

Rolling

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Linepipe

UOE (Seamwelded) Linepipe

U-Press

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Linepipe

UOE (Seamwelded) Linepipe

O-Press

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Linepipe


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Pipeline Design

Flow Assurance

Pipeline Type



Pipeline Stability

Pipeline Expansion


Pipeline Protection

Linepipe Material Selection

Base case = carbon steel

High strength, low cost, readily available - But is it adequate?

Typical grades are X42, X52, X60, X65, X70 (Number refers to yield in ksi).

Requires injection of corrosion inhibitors.

Corrosion resistant alloys - For corrosive fluids

13 chromium martensitic stainless steel

316L austenitic stainless steel

Duplex or Super Duplex Stainless Steel

Clad Steel – same corrosion resistance on inside, but only part of the pipe wall is

corrosion resistant

Selection depends on levels of CO2, H2S, chlorides and oxygen

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Material Selection

Corrosion Protection

Internal Corrosion

Increasing of wall thickness (Corrosion

Allowance)

Lined Pipe

External Corrosion

Cathodic protection (anodes)

“Half-shell” form

Attached to pipeline via electrical continuity lead

External corrosion coatings

Fusion bonded epoxy (FBE)

Asphalt enamel

3-layer polypropylene (PP) or polyethylene (PE)

systems

Neoprene/EPDM

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Corrosion Protection

Insulation Coatings

Transient conditions: Insulation required to maintain the minimum arrival

temperature (U Value)

Cool-down: Maintain enough heat in system during shutdown (function of density

and Cp of insulation material)

Coatings may be wet (external to steel) or dry (Pipe in pipe)

Insulation coatings

Foam or syntactic based polymers

Must withstand external pressure and operating temperature for full field life

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Wet Insulation

Material Capabilty Chart

0

20

40

60

80

100

120

140

160

180

0 1000 2000 3000 4000

Water Depth/m

Te

mp

era

ture

C

Typ

ic

al G

SP

U

De

ep

W

ate

r

Typ

ic

al G

SP

U

Mid

w

ate

r

de

pth

Typ

ic

al G

SP

U

Low

e

nd

w

ate

r

de

pth

Typ

ic

al S

PU

Typ

ic

al S

olid

P

U

Typical Deepwater PP

K value

>0.1 W/m.K

Insulation Coatings

Typical 0.15 - 0.18 W/m.K

>0

.2

W

/m

K

0.165 - 0.185 W/m.K

NB Wet temperature

capability


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Pipeline Design

Flow Assurance

Pipeline Type



Pipeline Stability

Pipeline Expansion


Pipeline Protection

Pressure Containment

Collapse Strength

Propagation Buckling

Installation Loads

Pressure Containment

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Pipeline Failure Mechanisms

Collapse

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Local Buckling

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Buckle Propagation

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Pipeline Design – Propagation Buckling

Deepwater Phenomenon

Local Collapse Runs Along Pipeline

Buckle Propagates at High Speed


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Pipeline Design

Flow Assurance

Pipeline Type



Pipeline Stability

Pipeline Expansion


Pipeline Protection

On-bottom Stability

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Lift Force

Drag and Inertia ForcePipe Weight

Seabed Friction and

Passive Resistance

Pipeline Design – Stability

Pipelines are subject to wave/current action

Must be stable on the seabed

To Improve On-bottom Stability

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Pipeline Design – Stability

Add weight. Thicker steel wall thickness or concrete coating

Trench below the seabed to shelter the pipe

Rock dump

Add concrete mattresses


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Pipeline Design

Flow Assurance

Pipeline Type



Pipeline Stability

Pipeline Expansion


Pipeline Protection

Operating Pressure and Temperature

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Pipeline Design – Thermal Loads

The effective axial force is composed of

Thermal effect

Pressure (“hoop stress”) effect

Pressure (“effective axial force”)

Residual lay tension

Typical Expansion Spools

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Pipeline Design – Expansion Spools


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Pipeline Design

Flow Assurance

Pipeline Type



Pipeline Stability

Pipeline Expansion


Pipeline Protection

P

P

Buckling Force

• Imperfection required to initiate buckle.

Pipeline Buckling

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Upheaval Buckling

Buried pipeline breaks through backfill.

Lateral Buckling

Pipe on seabed deflects laterally.

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Lateral

Buckling

Upheaval

Buckling

Pipeline Buckling

Buckling

Add backfill soil cover and / or rock cover

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Mitigating Upheaval Buckling Design

Mitigating Lateral Buckling Design

• Add rock cover to prevent buckling

• Allow buckling to occur at initiated points

• Lay S-Shape on Seabed

Typically 1-2 km pitch

Typically 1 km

Pipeline Buckling

Buckling mitigation


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Pipeline Design

Flow Assurance

Pipeline Type



Pipeline Stability

Pipeline Expansion


Pipeline Protection

Protection

Pipelines can be hit by

Dropped objects

Fishing gear

Anchors

Pipelines can withstand impact … up to a point

Denting damage is evaluated from impact energy

Protection determined on risk assessment

Pipelines – trench or rockdump

Spools – rockdump, mattresses, concrete tunnels etc.

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Pipeline Design – Protection

Pipeline Protection

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Rockdumping and Matressing

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Pipeline Protection

Ploughing and Jetting

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Pipeline Protection

Trenching and Protection

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Pipeline Protection


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Flow Assurance

Pipeline Diameter



Pipeline Stability

Pipeline Expansion


Pipeline Protection

Pipeline Protection

3. Pipe Installation

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Installation

Pipeline Installation

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4 main pipeline installation techniques

Reel-lay

S-lay

Bundle

J-lay

Reel-Lay

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Deep

< 3000m

Spoolbase

Stalks Fabricated from single pipes

12.2m pipes are welded

Quality checked (NDT)

Field joints are applied

Typically 1Km stalk lengths

Completed Stalk Racks

Stalks on racks awaiting vessel

for spooling

Vessel spools stalks onto reel

Reel lay

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Equipment and Function

Reel-Lay

Technip’s Pipelay Vessel Apache (2”-16” Pipe)

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Reel lay

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Seven NavicaPipe to 16” Capacity 2200Te

CSO ApachePipe to 16” Capacity 2000Te

Vessel examples

Piggyback Installation

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Installing more than one line together

Reeling Summary

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Advantages

Small offshore spread

Lay Vessel

Survey Support Vessel

Onshore fabrication of pipeline

High lay rate

Disadvantages

Smaller pipe diameter limits

More plastic bending and straightening of the pipeline

Limitation in coatings

Concrete weight coated pipe cannot be installed by reeling

Pros and cons

S-Lay

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Depth

<3000m

S-lay Operations

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Global 1201

• 162m Long

• 38m Wide

• DP Class 2

• 105m Long Stinger (Deep water)

• 39m Long Stinger (shallow water)

• 6400te Pipe Tension Capacity

• 4” – 60” Pipe

• 10 Work stations

S-Lay

Advantages

Large Pipe Diameter Range: 6 – 60” Dia

Concrete Weight Coated Pipe

Cost Effective for Long Pipelines or Campaigns and remote operations

Disadvantages

Operational Costs

„Deep‟ Water Depth Limits

Slow Transit & Operational Speeds

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S-Lay

Pros and cons

Bundles

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Bundle components

Bundles

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Bottom-Tow Bundle (GoM)

Controlled Depth Tow Method (North Sea)

Bundle Summary

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Advantages

Multiple Pipelines in Single Operation

Onshore Fabrication

Disadvantages

Repairs are Difficult

Suitable Fabrication Site Locations

Extensive Route Surveys

Pipeline Crossing Agreement

Pros and cons

J-Lay

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Very Deep

>2000m

J-lay – Vessels

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CSO Deep Blue Saipem 7000

J-lay Summary

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Advantages

Deepwater Capability

Large Pipe Dia. Range

Disadvantages

Reduced Layrate – Single Work Station

Requires Continuous Re-Supply of Pipe

Pros and cons

The end…..

Any Questions?

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Documents

SUT - Subsea Awareness Course - EW Feb 2012 Rev 1