12 - Subsea equipment

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Subsea production systems

Materials Technology for Offshore Oil and Gas Installations

Slide 2

Objectives

At the end of this module you will have basic knowledge about:

Criteria for material selection wrt. subsea production systems

Fabrication welding of subsea processing equipment

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Slide 3

Subsea productions systems

Most frequently used design code is ISO 13628.

Covers:

- Manifolds

- Risers

- Wellheads and tree equipment,

- Flexible pipes,

- Umbilicals

- Valves,

- Etc.

WellheadX-mas tree

Tie in structures and modules

Material selection in subsea production systems

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Slide 5

NORSOK M-001 – Material selection

Wellhead equipment / X-mas trees for production

13Cr4Ni, Low alloy steel with Alloy 625 overlay

Wellhead equipment / X-mas trees for deaerated seawater

Low alloy steel with Alloy 625 overlay in sealing surfaces

Wellhead equipment / X-mas trees for aerated seawater

CMn-steel with weld overlay

Wellhead equipment / X-mas trees for produced water and aquifer water

13Cr4Ni, Low alloy steel with Alloy 625 overlay

Retrievable equipment internals 13Cr or CRAs with higher PRE

Non-retrievable equipmentinternals

Alloy 718 or CRAs with higher PRE

Material selection for wellheads and X-mas trees

Slide 6

Piping systems for well fluids

6Mo, 22Cr duplex, 25Cr duplex.

Piping for deaeratedseawater

6Mo, 22Cr duplex, 25Cr duplex. CMn-steel can be used for shorter design life.

Piping for gas CMn-steel, 22Cr duplex, 6Mo

Piping for produced water and aquifer water

22Cr duplex, 25Cr duplex, 6Mo.

Piping for raw seawater 25Cr duplex, Titanium.

Hydraulicfluids/glycol/methanol

316

Chemical injection andannulus bleed systems

316

Retrievable valve internals 13Cr, 17 - 4 PH, Alloy 718

Non-retrievable valveinternals

Alloy 718

Material selection for manifold piping

Purpose of manifold module:- Interface between wells and

pipelines;- Collect produced fluid- Distribute produced fluid,

inject inhibitors, inject gas, control fluid;

- etc.

NORSOK M-001 – Material selection

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Slide 7

NORSOK M-001 – Material selection

Oil and gas CMn-steel, 13Cr, SM13Cr6, 22Cr duplex or CMn-steel with CRA cladding

Deaerated seawater injection CMn-steel, internal organic lining may be used

Produced water and aquifer water injection

CMn-steel, CMn-steel with internal organic lining, 22Cr duplex, 25Cr duplex or 6Mo

Raw seawater injection Ti, 6Mo, 25Cr duplex, CMn-steel with internal organic lining.

Material selection for rigid flowlines

Slide 8

Test coupon for mechanical testing

Where should the test coupon be located?

Note: The example refers to test coupon taken from a prolonagtion of the actual forging

Depends on: - Design Code

- Additional Purchasing Reguirements)

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Slide 9

Test specimen for mechanical testing

Where should the test specimen be located?

Note: The example refers to test coupon taken from a prolonagtion of the actual forging

Depends on: - Design Code

- Additional Purchasing Reguirements)

Welding in subsea production systems

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Slide 11

Welding of low alloyed Q/T steels

Base Materials: Often high strength low alloy Q/T steel

Welding:

- Difficult to weld due to high strength low alloy steels

- If PWHT is carried out, check the tempering temperature of the material

Weld

Slide 12

Materials with CRA overlay welding

Applicable for:

- Valves

- Hubs/connectors

- Wellhead equipment

- X-mas tree equipment

- Etc.

Weld overlay

Subsea processing equipment and components are typically processed from CMn-steels or low alloy steel with use of internal weld overlay

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Slide 13

Typical weldment for termination heads

Pipeline

Duplex steel

Pup piece

Duplex steel

Hub

Low alloy steel

Duplex/InconelDuplex

Why is this weld typically carried out by the termination head manufacturer?

Slide 14

Typical weldment for termination heads

Pipeline

Duplex steel

Pup piece

Duplex steel

Hub

Low alloy steel

Duplex/InconelDuplex

Buttering with e.g. Inconel 625 - One PWHT cycle enough if both cladding and buttering carried out at same manufacturer

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Slide 15

Welding of valve body to transition piece

Valve body

- Low alloy steel with CRA clad – PWHT after cladding necessary

Transition piece

- CMn steel with CRA clad - PWHT after cladding not necessary

- or stainless (duplex)

How to avoid new PWHT after butt welding?

Slide 16

Welding of valve body to transition piece

Valve body

- Low alloy steel with CRA clad – PWHT after cladding necessary

Transition piece

- CMn steel with CRA clad - PWHT after cladding not necessary

- or stainless (duplex)

How to avoid new PWHT after butt welding?

- Buttering

- Alternatively pup piece

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Slide 17

Buzz groups

Why is PWHT necessary when welding on low alloy steels?

Why is it important to reduce the number of PWHT’s?

How should the clad welding in the butt weld configuration be qualified?

Slide 18