barents 2020 working group 2

Lars Ingolf Eide 08 December 2010

Barents 2020 Working Group 2

Barents 2020 Conference Meeting Moscow December 8, 2010

© Det Norske Veritas AS. All rights reserved.


08 December 2010

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Working Group RN02 – Guidance to ISO 19906 for design of stationary floating installations against ice-loads

Deliverables:- Agreed Guidance Document for design against ice loads on stationary floating structures that may serve

as a common Russian-Norwegian separate supplement to ISO 19906 for the Barents Sea. The Guidance Document that may be submitted, partly or in full, to ISO for their consideration in connection with the first update of ISO19906.



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Barents 2020 Phase 4 – Working Group 2 MembersRussian team Norwegian/OGP teamMarat N. Mansurov, VNIIGAZ, Coordinator

Marina M. Karulina, Krylov Shipbuilding Res. Inst

Irina A. Surikova, Russian Maritime Register of Shipping, TK 318

Sergei D. Kim, VNIIGAZ

Pavel Liferov, Shtokman Development AG

Nina Krupina, Arctic and Antarctic Res. Inst.

Yury Nemenko, Giprospetsgaz

Vakhtang M. Glonti, Gazprom

S.I Zibakin, Gazprom Shelf Production

Gleb Churkin, Agency of researches of industrial risks (observer)

Valery P. Nekrasov, Ministry of Emergency Measures of the Russian Federation (observer)

Vladimir A. Pestryaev, Sakhlinnipimorneft

Rod Allan, Transocean

Arne Gürtner, Statoil

Hans Martin Sand, Moss Maritime

Jean-Marc Cholley, Total/OGP

Graham Thomas, BP/OGP

Mike Orr, Cairn Energy/OGP

Guido Kuiper, Shell/OGP

DNV:

Per Olav Moslet,

Lars Ingolf Eide, Coordinator



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RN02 - Status In-depth review and gap analysis by SDAG and

Statoil, comments to more than 75 sub-clauses Voluntary contributions from participants; assigned tasks for topics Revised work plan Rough layout of final report



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Review of ISO 19906; example, one out of 16 pages



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Review of ISO 19906; example, one out of 16 pages



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Contribution list; one half out of four pages



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Some issues

Ice Management (IM) and impact on floater design- Can IM be used to reduce design loads? If yes, how and what are requirements to documentation?

Ice model testing, floaters- Details missing

Ice data- How to handle sparse data statistically?



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Ice Management (IM) and impact on floater design Safety level and system reliability

Barents 2020 objective is to achieve similar safety level as in the North Sea

System reliability is a function of the component reliability of the structure and the efficiency of the components in the Ice Management (IM) system

System reliability

Structure reliability IM efficiency

Taking into account the reliability of compontents in IM system



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Ice Management (IM) and impact on floater design Design, ice management and disconnection

“Any ice management approach that is intended to support the operation of an offshore system (floating, fixed, subsea or otherwise) shall be configured to achieve an acceptable level of overall system reliability, in combination with structural resistance. The acceptable level of system reliability should be determined according to the principles set out in Clause 7 over the design service life of the system(s) the ice management system is supporting.”

IM philosophy

Design philosophy Disconnectionphilosophy

Reflect overall system reliability



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Ice Management (IM) and impact on floater designManaged ice

Gap analysis:- Reduction of design ice actions resulting from design ice features (i.e EL or AL level) is not

obvious. No guidance on methodology is offered. - Adverse effect should be identified

Contributions:- Documentation of reduction of design ice actions resulting from design ice features (i.e EL or

AL level) in case of IM.- Quantification of the effect of ice management as well as the impact of the chosen design

philosophy on the overall design- Summarize general findings and learnings from managed ice to be determined from full-

scale experience from Kulluk. - Assess adverse effects arising from Ice Management (ISO requirement). A list of so-called

‘adverse effects’ to be be provided



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Ice model testing of floaters Gap:

- No particular guidance offered for testing of floating systems in ice tanks.- Details missing

Contributions:- Performance requirements

for model testing of floaters to be provided

- Assessment of deviations between two modelling approaches:- towing or pushing the model

through a stationary ice sheet; - pushing the ice sheet towards

the stationary model;- Note that ice model test results

should be corrected according to actual obtained ice characteristics in order to make them comparable to full scale



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Ice model testing of floaters (2) Contibutions:

- Outline of special requirements to mooring system;- Moored system stiffness to be

quantified in model scale and compared to prototype design;

- Pull-out tests should be performed to assess the model scale mooring system;

- Decay tests should be performed for deriving the natural periods of the model in open water;

- Note on assessment of ice-structure friction coefficient to be assessed in model scale;

- Note on importance of logging structure motions and accelerations, i.e. degrees of freedom, for various structure types

- Notice on determination of rubble parameters for ice ridge characteristics in model tests, such as rubble strength and density



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Ice data Identifed gaps:

- Estimating statistical distributions for sea ice and icebergs based on fairly limited databases should be addressed.

- How to handle limited data sets in general. Consider distributions for probabalistic calculations or define parameters or, when no data, recommend on parameters

Contributions will include improved guidance on- Considerations on data requirements- Characterization of ice drift- Defining ice properties that can not be

readily measured in the field- Definition on ice concentration- Ice berg shape coefficients, iceberg

adverse shapes and iceberg stability- Expert judgement on physical and

mechanical properties of ice



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Ice data – contributions continued

Additional guidance on handling of limited data sets. Objective shall be to define distributions (with focus on tails and cut-offs) for probabilistic load calculations and not least define deterministic parameters for deterministic load calculation checks (in particular for AL). Where no data is available, recommendations shall be provided on which parameters to use.

Additional guidance to be provided on i) interpretation of satellite data; ii) variability of ice drift; iii) geophysical scale ice pressure

Analysis of satellite imagesFast ice

ENVISAT ASAR WS subimage for March 31, covering Surovaya Bay in Hall Island, Landsat subimage of Surovaya Bay for March 20, and photo of icebergs from helicopter in Surovaya Bay. 1, 2 and 3 – marked icebergs.



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Layout of final report - proposal

Introduction- Brief Barents 2020 description and history

Description of work process

Gap analysis

Background information/justification for recommendations- For each recommended supporting text, a brief descripription on the basis/background

Recommendations on supplementary text- Organized according to clauses in ISO 19906 where we suggest supporting text

Recommendations, other



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Proposed Work Plan 2011 Early March : Text proposals received by DNV

3rd week March: Draft text for guidelines from editing group/DNV

End March: 3rd group meeting, review texts, sort out issues; workshop

May 13: Draft report from DNV, including draft text for guidelines

End May: 4th group meeting, review texts, sort out issues, detailed plan for fall

End June: Revised texts from editing group/DNV

End August: Comments to latest revision

Mid September: Texts 90-95% complete, editing group/DNV End September: Discuss additional changes

Mid October: Distribution of revised texts, editing group/DNV

Early November: Comments to last version

Mid November: Final texts distributed, only cosmetics left

December: Last group meeting, cosmetic changes, preparation of presentations to Steering Committee and Plenary



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Thank you for the attention

Safeguarding life, property and the environment

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