Guideline for Structural Well Integrity - ptil.no 2012/Subsea... · DNV-OS-E101 General ISO 13628-1...

Lars Tore Haug2012-12-06

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Guideline for Structural Well Integrity

Status JIP and ongoing development work

© Det Norske Veritas AS. All rights reserved.


2012-12-06 DRAFT

Presentation Outline

Subsea wellhead system overview and industry experience

- wellhead integrity, complexity

- current industry approaches, main areas of uncertainty

JIP – Structural integrity of drilling and well systems

JIP phase 2 plans

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System Overview MODU Motions

Riser Movements and BOP motion

Well Construction, - WH relative movement / non-pre-loaded,

and pre-loaded designs

Seabed Support

Environmental Conditions

Stakeholders- Operator- Rig owner- Subsea manufacturer

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Background – wellhead function

- wellhead including conductor constitutes a crucial structural element within the entire drilling and well system.

- provides a safe well barrier during drilling of intermediate sections.

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Well Head

Conductor Housing

The function of the wellhead system.



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Typically the hotspots consists of:

Welds- On conductor and wellhead housings

- Shown in the two red dots higher up

Connectors- On conductor and wellhead housings

- Shown in the two red dots lower down

Base Material Transitions

30” conductor20” casing

13 3/8”9 5/8”

Background – Hotspots

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18 ¾” Subsea

wellhead



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Background - incidents

Few incidents experienced or reported:

West of Shetland 1983: A fatigue failure of a high pressure wellhead housing due to VIV west of Shetland [1]

North Sea 2005. Abnormal BOP movements were explained by a parted conductor casing extension weld, caused by fatigue [2]

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[1] Hopper, C.T., “Vortex Induced Oscillations of Long Marine Drilling Risers”, Proc.Deep Offshore Technology Conf., Malta, 1983.[2] Reinås, L., Sæther, M., Hørte, T., and Grytøyr, G., “Wellhead Fatigue Analysis Method,” Proc. of the International Offshore Mechanics and Arctic Engineering Conference Rotterdam, Netherlands, 2011.



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Lack of standards for wellhead There is no industry-wide standard or guideline available for subsea

wellhead calculation.- API 6a / ISO 10423 – Specification for Wellhead and Christmas Tree Equipment

(section 4.3.3.1):

- API 17d / ISO 13628-4 – Specification for Subsea Wellhead and Christmas Tree Equipment: (section 5.1.2.1.1):

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“Fatigue analysis and localized bearing stress values are beyond the scope of this International Standard”

“The effects of external loads (i.e. bending moments, tension), ambient hydrostatic loads and fatigue shall be considered.”



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Challenges – areas of uncertainty

Old subsea wells: Main driver for methodology developed in the Method Statement.- Issue in the North Sea: Template wells. Non-preloaded WH with 45° load shoulder (rocking

WH). Shallow water, harsh conditions.

Lack of design-, fabrication records and load history. - Change in industry required; new approach to handling contracts from early phase to finish;

operators, drilling contractors, wellhead manufacturers.

New subsea wells: Design basis, roles and boundary conditions- Challenging to quantify load early in the project.

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Challenges in fatigue assessment Critical hotspots are not accessible for inspection

Riser loads can be monitored, but there are still uncertainties on the resulting stresses in the hot-spots.

Strains or stresses in wellheads are not monitored

The logging results of cement between the high pressure housing and the low pressure housing are uncertain and provide little guidance to the analyst. - For new wells : It is possible to log through the surface casing

before installing intermediate casings, but there is a cost issue and uncertain results. Half a day of rig time.

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Joint Industry Project (JIP), Phase 1 - 2010 to 2012

Triggered by industry needs- Challenges in documenting integrity margins for both

static and dynamic loading

Demand for guidelines related to loading and capacity of the well system - in particular with respect to fatigue

Ensure a consistent approach for integrity of entire drilling and well systems

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JIP Participants Norwegian

Oil and Gas Association (observer)

Statoil (chair)

BG Group

BP

Det Norske

Eni

ExxonMobil

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Lundin

Marathon

Shell

Talisman

Total

Woodside

Nexen

GDF Suez

Chevron



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Scope & Deliverables, Phase 1

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Act 1 - State of the Art Review

Act 2 - Uniform Structural Design Philosophy

Act 3 – Fatigue Design and Calculations

Act 4 & 5 – Integrity and Information Management

Act 6 – Well Foundation

Act 7 – Work Group Contribution

Act 8 – Ultimate & Accidental Limit State Design

Act 9 – Fatigue Design, Alternative Analysis Method

Act 10 – Houston Work Group

TR1 – Structural Integrity Philosophy of Well System

TR2 – Capacity Design and Analysis of Well Systems

TR3 – Fatigue Design and Analysis of Well Systems

TR4 – Integrity and Information Management for Well Systems

DNV Guideline

Scope Intermediate deliverables Final deliverable

Objective to address the well systems’ structural integrity as a complete system.



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Part 1 – Safety Philosophy

Overall structural integrity philosophy- Based on overall safety principles as outlined in

existing DNV Offshore Standards- Adopting a safety class methodology (low,

medium, high)

Roles and responsibilities- Roles and responsibilities should be defined in

early phase- Normally operator’s responsibility to define

overall safety performance- Closely related to information and integrity

management

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TR 1

TR 2 TR 3

TR 4



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Part 2 – Structural Strength design and analysis Main objective to establish a uniform

method for assessing strength capacity of well systems.

Currently there are multiple methods presented in a range of international codes and standards.

The method will provide: - A bridge between established standards- A consistent safety level for overall system

To be handled in JIP phase 2

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TR 1

TR 2 TR 3

TR 4

Wellhead/XT:API 6aAPI 17dISO 10423ISO 13628-4

BOPISO 13628-7NORSOK D-001NORSOK D-010API Spec 6AAPI Spec 16AAPI RP 16EAPI RP 53API 16dAPI Spec 16C

Casing Tubing, DownholeISO 11960API 5ct(2)(3)API 14a(b)(h)(j)ISO 10426-1 (cement)

Drilling Equip.API 7KAPI RP 64API 4FAPI 8CDNV-OS-E101

GeneralISO 13628-1NORSOK D-001NORSOK D-010NORSOK U-001OLF Guideline 070PSA NorwayDNV-OS-C101

Riser/UmbilicalsISO 13628-2ISO 13628-3ISO 13628-5ISO 13628-7API RP 16QAPI Spec 16R DNV-OSS-302DNV-OS-F201DNV-RP-F206ISO 13624-2

Control SystemsISO 13628-6API Spec 16D

Well FoundationAPI RP 2A



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Part 3 – Fatigue analysis

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Describing important issues related to local and global analysis including: Mechanical behavior of wellheads

BOP dynamics

Tensioning systems

Flex joints

Soil

Main challenge: Sensitive to input parameters

Hydrodynamic properties of BOP and riser uncertain

Different analysis methodologies give incomparable results

TR 1

TR 2 TR 3

TR 4



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Part 4 - Information Management

Information management

Input information for analyses

Information flow

Structural well integrity process description

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TR 1

TR 2 TR 3

TR 4



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Adequacy of analysisPrevious calculation methods:

Insufficient fundamental description of the mechanical problem raised doubt, could be too simplified or wrong

Guideline focus on calculation methods:

Addresses complex mechanical behavior

opens for alternative methods, ref benchmark study

Recognizes following as key topics for future consideration- insufficient understanding of effect of important parameters- absence of properly calibrated wellhead strain/stress monitoring results

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Benchmark Study 2H Offshore, Stress Engineering Services and Statoil are performing analyses of a

test case

Purpose : - Assess and compare various methodologies for WH fatigue analyses

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New JIP phase 2, propose launch 2013 - Objective Further develop and revise/improve fatigue calculation methodology;

- Increased accuracy, increased flexibility (different approaches), benefit of monitoring

Systematic approach to analysis of ultimate and accidental load and capacity of the wellhead system.

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Improved fatigue calculation

methodology

Structural strength calculation

methodology



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JIP phase 2 - Scope1. Fatigue Analysis Methodology

Bench marking of fatigue analysis methods, case studies

Monitoring, guidance on implementation

Improvement, of fatigue methodology (fracture mech., strain life, global analysis ..)

Structural Reliability Analysis, Fatigue

Vortex Induced Vibrations (VIV)

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Riser load time series



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JIP phase 2 - Scope2. Structural strength; ( i.e. pressure, load, ultimate, extreme, accidental)

Identify industry best practices, identify risk and limitations and interfaces in present codes

Provide a Guideline to:- Numerical validation and handling of interfaces from a

systems perspective..- How to use existing codes for subsea applications- Guideline for common understanding of operating

envelopes of equipment

Supplement to ISO/API codes

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Summary The industry has not agreed on a unified approach to

how to address the challenges. Different methods exists.

JIP phase 2 is planned with kick off in January 2013

The Guideline is still “work in progress” and has not yet been approved for industry release by the Steering Committee.

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Safeguarding life, property and the environment

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Guideline for Structural Well Integrity - ptil.no 2012/Subsea... · DNV-OS-E101 General ISO 13628-1...

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