DRAFT Guideline for Structural Well Integrity

Draft 2012-11-20

Guideline for Structural Well Integrity Status JIP and ongoing development work Lars Tore Haug 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

Guideline for Structural Well Integrity 2012-12-06 © Det Norske Veritas AS. All rights reserved.

DRAFT 2

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


DRAFT 3

Background – wellhead function Well Head  The function of the wellhead system. Conductor Housing

- 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.


DRAFT 4

Background – Hotspots Typically the hotspots consists of:

18 ¾” Subsea wellhead

 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” conductor 20” casing 13 3/8” 9 5/8” Guideline for Structural Well Integrity 2012-12-06 © Det Norske Veritas AS. All rights reserved. 5

DRAFT

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]

[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. Guideline for Structural Well Integrity 2012-12-06 © Det Norske Veritas AS. All rights reserved.

DRAFT 6

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):

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

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

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


DRAFT 7

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.


DRAFT 8

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.


DRAFT 9

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


DRAFT 10

JIP Participants  Norwegian Oil and Gas Association (observer)

 Lundin

 Statoil (chair)

 Talisman

 BG Group  BP  Det Norske  Eni  ExxonMobil


 Marathon  Shell

 Total  Woodside  Nexen  GDF Suez  Chevron

DRAFT 11

Scope & Deliverables, Phase 1 Objective to address the well systems’ structural integrity as a complete system. Scope

Intermediate deliverables

Final deliverable

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

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

Act 10 – Houston Work Group Guideline for Structural Well Integrity 2012-12-06 © Det Norske Veritas AS. All rights reserved.

DRAFT 12

DNV Guideline

TR 1 TR 2 TR 3

Part 1 – Safety Philosophy

TR 4

 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


DRAFT 13

TR 1

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:

General ISO 13628-1 NORSOK D-001 NORSOK D-010 NORSOK U-001 OLF Guideline 070 PSA Norway DNV-OS-C101

TR 2 TR 3 TR 4

Drilling Equip. API 7K API RP 64 API 4F API 8C DNV-OS-E101

BOP ISO 13628-7 NORSOK D-001 NORSOK D-010 API Spec 6A API Spec 16A API RP 16E API RP 53 API 16d API Spec 16C

Riser/Umbilicals ISO 13628-2 ISO 13628-3 ISO 13628-5 ISO 13628-7 API RP 16Q API Spec 16R DNV-OSS-302 DNV-OS-F201 DNV-RP-F206 ISO 13624-2

- A bridge between established standards - A consistent safety level for overall system

Control Systems ISO 13628-6 API Spec 16D

To be handled in JIP phase 2

Wellhead/XT: API 6a API 17d ISO 10423 ISO 13628-4

Well Foundation API RP 2A


DRAFT 14

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

TR 1 TR 2 TR 3

Part 3 – Fatigue analysis

TR 4

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 Guideline for Structural Well Integrity 2012-12-06 © Det Norske Veritas AS. All rights reserved.

DRAFT 15

TR 1

Part 4 - Information Management  Information management  Input information for analyses  Information flow  Structural well integrity process description


DRAFT 16

TR 2 TR 3 TR 4

Adequacy of analysis Previous 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


DRAFT 17

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


DRAFT 18

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.

Improved fatigue calculation methodology

Structural strength calculation methodology


DRAFT 19

JIP phase 2 - Scope 1. 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)


DRAFT 20

Riser load time series

JIP phase 2 - Scope 2. 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


DRAFT 21

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.


DRAFT 22

Safeguarding life, property and the environment www.dnv.com


DRAFT 23