How is Wellhead fatigue handled by industry standards? Lorents Reins

2014-03-10 Classification: Internal

Objective

What is Wellhead Fatigue

Industry standards for Wellheads

Design approach in the industry standards

Is this design approach suited for fatigue?

Industry standards look-ahead

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Today: 25th march 1950 Ski jump competition in London

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The ski-jump competition was never held again,

despite several attempts to revive it. The ski-jump

on Hampstead Heath was among the last major

events to use real snow to re-create ski conditions.

The first artificial snow was made two years later,

in 1952, at Grossinger's resort in New York, USA.

The competition was held on a

specially-built ski jump on the Heath

*BBC archives: http://news.bbc.co.uk

An official said of the event:

This exhibition has

been such an unqualified success that we are

very much hoping it will become one of the

country's major sporting features

What is Wellhead Fatigue?

Environmental energy is absorbed and

transmitted to the subsea well by the

MODU, BOP and riser.

Cyclic external loading of upper part of

subsea well

Resisted by material stresses in upper

well region.

Main symptoms expected in the wellhead

system

Exposure during drilling, not production

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WH fatigue

Fatigue is a time (usage) dependent

deterioration mechanism

Other time (usage) dependent

deterioration mechanisms are

Corrosion

Wear

HISCC

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ISO 13628 Series Code Break

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API ISO truce has ended

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Timeline API 17D

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ISO 13628-4 design approach

Basically a pressure vessel design approach: pressure loads are used in

design

In ISO 13628-4, section 5.1.3 Design Method, it reads: The effects of external loads (i.e. bending moments,

tension etc.) on the assembly or

components are not explicitly

addresses in this part of ISO 13628 or

ISO10432. As equipment covered by

this part of ISO 13628 are exposed to

external loads, ISO 13628-7 may be

used to define the structural strength

design.

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Fundamentally Different Design Methodology

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ISO 13628-4 ISO 13628-7

Rated load method Limit state method

A component is rated for a pressure

System integrator need to check

loading vs. rating.

Go/no-go decision

A component failure capacity is stated

Component manufacturer states

the limiting capacity

The code gives utilization of limit

System integrator to check system loads

vs. component capacity

Margin to failure is unknown

on a system level

Margin to failure is known

on a system integration level

Well Integrity definition

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an application of technical, operational and organizational

solution to reduce risk of uncontrolled release of formation

fluids throughout the life cycle of the well *

*NORSOK D010 Well integrity in drilling and well operations

Is the international design code for subsea wellhead equipment meeting regulatory expectations in Norway ?

No

i.e need for additional requirements if an

operator is purchasing subsea wellhead

equipment for use in Norwegian waters.

company specific type, but the future

might bring more unified additional

requirements

Such work towards recommended

practice documents is underway with

the ongoing JIP

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Regulatory bodies can impact standards

WH products are designed and manufactured for a global market

The design process is influenced by API

Approx. 90 buyers of WH,s

4-5 WH suppliers

2 ways ahead:

unified additional requirements amongst 90 buyers

API to include guidance on system loads in design methodology

US governmental pressure needed

PTIL can make a difference

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Further readings

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ISO 13628-4

ISO 13628-7

Wellhead Fatigue Analysis : Surface casing cement boundary condition for subsea

wellhead fatigue analytical models Section 3: Reins, Lorents PhD thesis can be

downloaded at http://brage.bibsys.no/xmlui/handle/11250/191246

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Statoil setting new standards

together with the industry to

boost drilling efficiency and IOR

How is Wellhead fatigue handled by

industry standards?

Lorents Reins

Leading engineer

Rex@statoil.com

www.statoil.com

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