SUBSEA FORUM PARIS 2007

SUBSEA PIPELINES

YOUNG ENGINEERS DAY

SUBSEA FORUM PARIS 2007

Contents

• Introduction to pipelines

• Where do you as engineers fit in ?

• Diversity of the pipelines

industry

• Example projects

SUBSEA FORUM PARIS 2007

Different types of pipelines

Trunklines (export)

Large diameter gas transmission lines. 40” plus diameter, up to circa 1000 km

Interfield and Infield lines (flowlines)

Transporting oil or gas within / to fields. 6-20” diameter, few km up to approx 100 km Langeled Pipeline

•Transport 20bcm gas / year•44” diameter concrete coated, 1200km in length•150 -250 bar internal pressure•Steel rods for concrete sufficient for 3 Eiffel T !

SUBSEA FORUM PARIS 2007 CSO Constructor

CSO Apache

Example of a subsea field development

SUBSEA FORUM PARIS 2007

Where do engineers fit in today ?

Operators (owners)

Contractors (builders) Su

pp

liers

an

d T

ech

no

log

y I

nst

En

gin

eerin

g H

ou

ses (d

esig

ners)

DecommDecommProductionProductionImplementImplementEvaluationEvaluationDiscoveryDiscovery

SUBSEA FORUM PARIS 2007

Diverse disciplines and skills for newcomers

• Diverse disciplines

– Mechanics

– Geotechnics

– Dynamics

– Fluids

– Materials

• Diverse skills

– Concept to detailed design

– Analysis including F.E

– Technology development

– Code development

SUBSEA FORUM PARIS 2007

Globally diverse industry – exciting challenge !

•Geographical diversity of pipelines industry

•Varying levels of maturity

•Varying regulatory regimes (prescriptive or not)

•Different regions bring diverse technical challenges

•Multi-cultural

SUBSEA FORUM PARIS 2007

Diverse technical challenges

Deep water

Very shallow water

HP-HT

Aggressive gasses

Harsh Environments

Heavy oils

IRM

Decommisioning

Safety

Environment

Design for installation

Flow assurance

Insulated pipelines

Material selection and behaviour

Limit state pipeline design methods

Upheaval buckling

Lateral buckling and pipeline walking

Highly irregular seabeds

Spans and fatigue

Geohazards; routing, stability

Seismic

SUBSEA FORUM PARIS 2007

Project Examples

• Consulting

• Design

SUBSEA FORUM PARIS 2007

Technical Challenges – Lateral Buckling

• Many subsea pipelines operate under high pressure and temperature

• This generates large axial compressive forces in the pipe due to the frictional restraint from seabed

• The axial compressive force causes the pipeline to buckle laterally at an imperfection e.g out-of-straightness

• The pipeline will expand, feeding-in towards the buckle resulting in large lateral displacement, e.g 10m

• The bending moment and strains in the buckle apex could exceed the allowable limits and lead to local buckling or fracture and hence pipeline failure

• Advanced engineering analysis can be used to assess all aspects of this phenomenon

• The results can be used to determine effective mitigation solutions

SUBSEA FORUM PARIS 2007

Potential solutions

• Do nothing, prove lateral buckling

is ok without mitigation

• Expansion spools

• Snake lay

• Sleepers

• Buoyancy

• Intermittent rock dump

Safety ?Environmental Impact ?Cost ?Risk ?

SUBSEA FORUM PARIS 2007

Engineering from first principles – global analysis

SUBSEA FORUM PARIS 2007

Engineering from first principles – local analysis

SUBSEA FORUM PARIS 2007

Aqaba Pipeline Design

15km of 36” Pipeline across the Gulf of Aqaba. Part of a transmission system taking gas from Egypt to Jordan, Syria and then on to Turkey

SUBSEA FORUM PARIS 2007

Technical challenges

• Deepwater (remains the deepest water 36” pipeline). 856m at deepest point

• One of the most active seismicareas in the world. Egypt moves 2cm relative to Jordan annually. Pipeline designed to withstand 7.5 on Richter scale

• Steep slopes, deep gullies and long spans. Drop nearly 900m in 4km

• Environmentally sensitive (corals). Also lack of water meant that hydrotest was a problem

6km 3km4km

20 deg

SUBSEA FORUM PARIS 2007

Harsh environment

L1

L8L9

L2

L3

L4

L5

L6

L7

L1

L8L9

L2

L3

L4

L5

L6

L7

• High quality survey and current data allowed optimal route to be chosen to minimise spans

• Spans in deep water are very expensive to rectify using supports or rock

• Largest spans up to 450m were reduced to 220m by :

– Carried out advanced engineering using limit states

– Specified concrete half shells as overweight and mattresses

• Environmentally sensitive area (corals)

• Lack of water was a problem for hydrotesting the pipeline

– First pipeline in the world not to be hydrotested

SUBSEA FORUM PARIS 2007

Span analysis and route selection

-870

-850

-830

-810

-790

-770

-750

-730

-710

-690

-6704400 4500 4600 4700 4800 4900 5000 5100 5200

KP (m)

Wat

er D

epth

(m)

-580

-575

-570

-565

-560

-555

-550

-5453700 3725 3750 3775 3800 3825 3850 3875 3900 3925 3950

KP (m)

Wat

er D

epth

(m)

Pipeline

Seabed

Locat ion of KP3860m

SUBSEA FORUM PARIS 2007

Buckle arrestors

• High external pressure means that pipeline collapse due to buckle formation is an issue

• Most likely during construction

• Buckle will propagate at about the speed of sound !

• Mitigation is the use of buckle arrestors. The number and had to be designed

SUBSEA FORUM PARIS 2007

Ongoing inspection – Design versus actual

• Fatigue Life of and Installed Pipeline is Primarily Governed By :-

– Span Length

– Current and Wave Loads

– Distance to and Size ofAdjacent Spans

• Analysis Using Finite Element

– Determine the Modal Response

• Fatigue Life Calculated Based Upon

– DNV-RP-F105 : Free Spanning Pipelines

• Survey Quality of Free Spans is Important.

SUBSEA FORUM PARIS 2007

Summary

• Pipeline Engineering is diverse and challenging within the subseasector

• There is a significant shortage of engineers in our field, opportunities are therefore abundant for young engineers

• KW Ltd for currently have 2 ENSAM graduates working in their London office – we would be happy to talk to you.

Thank You