Impact of embedment on the thermal response of piliipelines. holbeach.pdf · Impact of embedment on...

Impact of embedment on the thermal response of i lipipelines.

Dr. James Holbeach, Staff ConsultantR i l M A t li MSi K

Experience that Delivers

Regional Manager, Australia, MSi KennyE: james.holbeach@msikenny.com W: +61 8 6314 2508 M: +61 417 553 757

Introduction: What?

• Precisely what you think!Burial / Embedment? What do we mean?

Precisely what you think!

Sea

Deeply BuriedS d / Deeply BuriedSand / mud

Unburied Partially Buried / Embedded

“Just” Buried

Experience that Delivers 1

Introduction: How?

• Three primary mechanismsThree primary mechanisms– Self Embedment– Metocean– Deliberate

Experience that Delivers 2

Self Embedment: Sea floor

Experience that Delivers 3

Self Embedment: Weight

Experience that Delivers 4

Metocean: Spaghetti plot

Experience that Delivers 5

Metocean: Cyclone/Hurricane/Typhoon/Big StormStorm

Experience that Delivers 6

Metocean: Sediment

Experience that Delivers 7

Metocean: currents

Experience that Delivers 8

Deliberate: Pipelay

Experience that Delivers 9

Deliberate: Trenching / Stability / Security

Experience that Delivers 10

Outline

• ContextContext• Case Study• PhysicsPhysics• Theory• Formulas• Verification• New tool

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Context:

• Mechanical issuesSo Why?

Mechanical issues• Stability Issues• Corrosion issues• What part do THERMAL issues play?

Experience that Delivers 12

Context

• Corrosion modellingThermal

Corrosion modelling• Buckling• Pipeline walkingp g• Hydrate management• Blowdown / low temperatures

TEMPERATURE CONTOUR PLOT IN A TEMPERATURE CONTOUR PLOT IN A PIPE CROSS SECTION

Experience that Delivers 13

Case Study

• Cooling section for corrosion: How long?Cooling section for corrosion: How long?

80 ºC 20 ºC80 ºC 20 ºC

Unins lated pipe

??m

Insulated pipeInsulated pipe Uninsulated pipe

Experience that Delivers 14

The problem

What’s so difficult?

Experience that Delivers 15

Physics: Partial Burial

• Unburied pipe U=20 W/m2KSurely you just

Unburied pipe U 20 W/m K• Just buried pipe U=10 W/m2K

• Half buried pipe U=15 W/m2K

• 25% buried pipe U=16.6 W/m2K

Experience that Delivers 16

Physics: State of play

Burial Level Knowledge levelBurial Level Knowledge level

Unburied Well understood

Deeply buried Well understood

Partially Buried Not well understood

“Just” buried Not well understood

Experience that Delivers 17

Physics: State of Play

• Old work– OLGA, Pipesim and Carslaw & Jaeger formulations approach the

unburied solution as burial depth -> 0m– Cant / should not use OLGA formulation for burial < ~1 Diameter.

A b i d t f tl i l t d ti– Assume buried component perfectly insulated - conservative

• “New” Work– Steady State- Morud et al (2007)– Steady State- Ovuworie (2010)

St d St t Z k i H lb h M (2012)– Steady State- Zakarain, Holbeach, Morgan (2012) – Steady State and Transient- MSi Kenny internal (2012+)

Experience that Delivers 18

Formulas

Experience that Delivers 19

Formulas

Experience that Delivers 20

Case study: What is important?

Tambient

• Overall heat transfer coefficient

q (heat flux)

Overall heat transfer coefficient– Three resistances– Straight forward calculation Tfl id

g– Often hin can be ignored

Tfluid

Inner film (hin) Pipe wall (kwall) External film (hex)

Experience that Delivers 21

Verification: Colourful Figures and Diagrams (CFD)Diagrams (CFD)

Experience that Delivers 22

STREAMLINES COLOURED BY VELOCITY MAGNITUDE [m/s] – CASE R2V09T065B050

Verification: Colourful Figures and Diagrams (CFD)Diagrams (CFD)

Experience that Delivers 23

TEMPERATURE CONTOUR PLOTS [°C] – CASE R2V09T065B050

Cooling Section

Cooling Section Sizing?

Experience that Delivers 24

Cooling Section

Cooling Section

Unburied Pipe 7 7kmUnburied Pipe = 7.7kmConservative = 13kmOptimised = 10.5 km

Saving: ~$20mil / line

Experience that Delivers 25

Ramp-up

T=0 hr

Experience that Delivers 26

Ramp-up

t=0.75 hr

Experience that Delivers 27

Ramp-up

t=1.00 hr

Experience that Delivers 28

Ramp-up

t=1.25 hr

Experience that Delivers 29

Ramp-up

t=1.50 hr

Experience that Delivers 30

Ramp-up

t=1.75 hr

Experience that Delivers 31

Impacts

• Cooling Section length OptimisationTemperature profiles

Cooling Section length Optimisation• Difference in Buckling design• Hydrate management philosophiesy g p p• Temperature management for hydrate remediation• Wax management

Experience that Delivers 32

Challenges

• No one formulation covers all casesModelling challenges

No one formulation covers all cases• Problems with incorporation in commercial software packages• No complete transient solutions ... Work in progressp p g• No clarity on external heat transfer coefficient (esp for natural convection)

Experience that Delivers 33

Acknowledgements

• Erich Zakairain (Woodside / Schlumberger)Erich Zakairain (Woodside / Schlumberger)• Prabu Parthasarathy (MSIK – Regional Manager India)• Christian Chauvet (MSIK- Lead CFD)( )• Woodside (esp. Paul Millachip / Julie Morgan)

Experience that Delivers 34