117 NORWEGIAN OIL AND GAS RECOMMENDED GUIDELINES FOR WELL INTEGRITY

117 NORWEGIAN OIL AND GAS RECOMMENDED GUIDELINES FOR WELL INTEGRITY

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 2 Preface This guideline is supported by Norwegian Oil and Gas Association's Resource Group Drilling Drilling Managers Forum (DMF) and recommended by Well Integrity Forum (WIF) and by Norwegian Oil and Gas' Committee for Operations. Further it has been approved by Norwegian Oil and Gas general director. The work group has been composed of the following members: Tommy Skjerven, BP; Øyvind Lunde, ConocoPhillips; Morten Perander, Eni Norge; Bruce Williams, ExxonMobil; Rod Farquhar, Marathon; Jean-Claude Sinet, Nexen Inc.; Jan Sæby, Norske Shell; Hilde Brandanger Haga, Statoil; Ørjan Finnseth, Talisman Ståle Johnsen, Total. Responsible manager in Norwegian Oil and Gas is Manager Drilling who can be contacted at the Norwegian Oil and Gas switchboard + 47 51 84 65 00. The guidelines express a joint solution developed between the operating companies including support from the Petroleum Safety Authority (PSA). These Norwegian Oil and Gas guidelines have been prepared with the broad-based participation of interested parties in the Norwegian petroleum industry, and they are owned by the Norwegian petroleum industry, represented by Norwegian Oil and Gas. Norwegian Oil and Gas is responsible for administration of these guidelines. Norwegian Oil and Gas Association Vassbotnen 1, Sandnes P.O. Box 8065 4068 Stavanger, Norway Tel.: + 47 51 84 65 00 Fax: + 47 51 84 65 01 Web site: www.norskoljeoggass.no E-mail: firmapost@norog.no NOTE: Revision 4 dated 06.06.2011 is issued to add Chapter 6

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 3 Index CHAPTER 1... 7 WELL INTEGRITY TRAINING... 7 1. Introduction... 7 2. Abbreviations... 7 3. Background... 7 4. Training Guidelines... 8 Appendix A... 9 Well Integrity Fundamentals Training recommended subjects... 9 CHAPTER 2... 11 WELL HANDOVER DOCUMENTATION... 11 1. Introduction... 11 2. Background... 11 3. Discussion... 11 a. Well Construction Data... 12 b. Well Diagrams... 12 C. Handover Certificate... 12 d. Operating Input... 13 CHAPTER 3... 14 WELL BARRIER SCHEMATICS FOR THE OPERATIONAL PHASE... 14 1. Introduction... 14 2. Background... 14 3. Guidelines of minimum data... 14 4. Discussion on minimum data... 15 4.1 The formation strength should be indicated for formation within the barrier envelopes... 15 CHAPTER 4... 19 WELL INTEGRITY WELL CATEGORIZATION... 19 1. Objective... 19 2. Abbreviations & Definitions... 20 Abbreviations... 20 Definition of terms... 20 3. Background... 21 4. Philosophy... 22 5. Use of Categorization System... 23

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 4 Categorization approach... 23 Information required for categorization... 24 6. Category Descriptions... 25 Overview of Category Principles... 25 Green Category... 26 Yellow Category... 29 Orange Category... 31 Red Category... 33 7. Attachment A - Well categorization description comparison table... 34 8. Attachment B - Well with casing cement not fulfilling Norsok D-010 acceptance criteria... 36 CHAPTER 5... 40 WELL INTEGRITY MANAGEMENT SYSTEM... 40 1. Objective... 40 2. Abbreviations... 41 3. Background... 42 4. Elements in a Well Integrity Management System... 43 5. Discussion of each main element... 45 5.1 Organisation... 45 5.2 Design... 45 5.2.1 Technical standards... 46 5.2.2 Barriers... 46 5.2.3 Equipment requirements... 46 5.2.4 Safety systems... 46 5.2.5 ALARP principle... 47 5.3 Operational Procedures... 47 5.3.1 Operate within the design load limits... 47 5.3.2 Monitoring, verification and maintenance program... 48 5.3.3 Well control and emergency preparedness... 48 5.3.4 Transfer of information... 48 5.4 Data system... 48 5.5 Analysis... 49 6. Appendix A summary of the regulations relevant for a WIM system... 50 Chapter 6... 54 Sustained Casing Pressure... 54

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 5 1. Objective... 54 2. Abbreviations & Definitions... 55 2.1 Abbreviations... 55 2.2 Definition of terms... 55 3. Sustained Casing Pressure Definition... 56 4. Sustained Casing Pressure Management... 57 4.1 Monitoring & Detection... 57 4.2 Evaluation... 60 4.2.1 Evaluation of source, mechanism and location... 60 4.2.2 Leak rate evaluation... 63 4.2.3 Annulus pressure evaluation... 63 4.2.4 Hydrocarbon gas volume and mass evaluation... 64 4.2.5 Escalation potential evaluation... 64 4.3 Acceptance Criteria Determination... 65 4.3.1 Leak rate criteria... 65 4.3.2 Annulus pressure criteria... 66 4.3.2.1 Failure Modes... 67 4.3.2.2 Fluid Densities... 68 4.3.2.3 Degradation of Tubulars... 68 4.3.2.4 Safety Factors... 68 4.3.2.5 Maximum Operational Pressure (MOP)... 68 4.3.2.6 Hydrocarbon gas mass... 69 4.3.2.7 Degradation of tubulars... 69 4.3.3 Hydrocarbon gas mass criteria... 70 4.3.4 Escalation potential criteria... 71 4.4 Mitigating Measures... 71 4.4.1 Technical... 71 4.4.2 Operational... 72 5. Sustained Casing Pressure Prevention & Elimination... 75 5.1 Well Design and Operational Considerations... 75 5.2 Pumping Operations... 77 5.3 Workover & Interventions... 79

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No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 7 CHAPTER 1 WELL INTEGRITY TRAINING 1. Introduction The Well Integrity Forum (WIF) was established in 2007 and one of the main issues that was initially brought up for review was well-integrity training. WIF members acknowledge a need for well-integrity training of key personnel working with well integrity offshore and onshore. This was also one of the key findings in an earlier PSA well-integrity survey. A survey of operators well-integrity-training practices, experiences, opinions and ideas was carried out and used as a basis for developing a well-integrity-training guideline. This chapter describes WIF members recommendations for well-integrity training and is intended to function as a guideline to the oil industry. 2. Abbreviations ASV is Annulus Safety Valve HSE is Health, Safety and Environment OIM is Offshore Installation Manager PSA is Petroleum Safety Authority SCSSV is Surface Controlled Subsurface Safety Valve WBS is Well Barrier Schematic WIF is Well Integrity Forum 3. Background A survey was completed by WIF members and this formed the basis for discussion and development of the guidance in section 4. The feedback focused on learning, present practice, opinions and ideas. The survey included the following questions: Main objective for a well integrity course? What should be covered in the well integrity training? Should the course include any exercises? Timing and schedule, how many days and if applicable, when?

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 8 Who to participate and mixture of skills in one group? Handouts and/or documentation? Computer based vs. class room based or other methods? Training a part of competency management system? 4. Training Guidelines What to cover in a well integrity course and timing of training The recommended training is listed below in a preferred sequence and with estimated number of training days for each element. Note that this recommendation applies to all personnel with assigned responsibilities for well maintenance, operations, servicing, design and construction. 1. Well Integrity Fundamentals (see Appendix A) Typically 1 to 2 days 2. Norsok D-010 terminology and principles Typically 1 day 3. Company specific training (test procedures, well design and internal requirements) Typically 1day Who should participate? Personnel directly responsible and or involved in Well Integrity should have the recommended training. Examples of who may be required to have this training are as follows: 1. Production operation personnel offshore (including OIM, production supervisors, control room operators, technicians and senior technicians); 2. Production operation personnel onshore (incl. Ops sup, production engineers, production technologies, HSE personnel); 3. Drilling/completion/intervention engineers (including drilling supervisor and drilling superintendent); 4. Rig contractors like drillers and tool pushers; and, 5. Service-company engineers and operators with delegated responsibilities in well integrity. Each company should evaluate on as per needs basis who in their workforce is required to attend the recommended training.

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 9 It is recommended that management responsible for Well Integrity should be trained. Type of training Class room based versus computer based Class room training is preferred for company specific training. Both class room based and computer based training is good for training in Norsok D-010 and well integrity fundamentals. Particularly for the computer based training method, it is recommended that the training include exercises, case solving and questions and be completed with a test. Additionally for class room training it is recommended to include group work exercises. Appendix A Well Integrity Fundamentals Training recommended subjects. 1. Roles and Responsibilities for Well Integrity Who monitors / who do they report to / who fixes? Who manages the Well Integrity System? 2. Basic Wellbore Physics Discuss formations / pressures / overbalance / underbalance / temperature increases when wells flow etc. Illustrations should be available to describe what is happening. 3. Basic Well Construction with Emphasis on Barriers Describe minimum barrier requirements. Provide a typical Well Schematic. Discuss tubing burst / collapse etc. Discuss SCSSVs / ASVs / Xmas trees / tubing. Schematics, incl. WBS and cutaways should be provided. 4. Basic Well Control Requirements Discuss and describe simple hydrostatics for well control. Discuss and describe Well Emergency Shutdown functionality. 5. Well Integrity Hazards Use case studies. Discuss hydrates / sand / corrosion - erosion / Well Intervention Ops etc. Well start up/shut down. 1. Annulus Monitoring and importance of reporting / trending. 2. Discuss operating and design limits (pressure, temperature, flowrates etc). Describe and provide typical Annulus Monitoring Spreadsheet. 3. Discuss annulus leak rate and other acceptance criteria. Discuss risk resulting from annulus leaks. 6. Annulus Bleed-Down

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 10 Discuss what should be reported and the reasons for bleed-down during production. Discuss sources of tubing to annulus communications - eg; pipe / cement etc. 7. Wellhead Maintenance Activities Discuss importance of regular and adequate well maintenance. SCSSSV Testing - discuss frequency / acceptance criteria / functionality / control line integrity /repeat tests Xmas Tree Valve Testing - discuss functionality / acceptance criteria Void Monitoring - discuss implications for hydrocarbons in voids / repair methods Monitoring equipment, accuracy and maintenance 8. Handover of Wells Need to ensure accurate and timely reporting. Discuss information required and who gets it. Provide an example Well Handover Documentation. 9. Documentation Discuss need for keeping good well integrity records. Discuss and describe need for non-conformance system for operating wells not in accordance with the 'Standard'. Provide an example.

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 11 CHAPTER 2 WELL HANDOVER DOCUMENTATION 1. Introduction The Well Integrity Forum (WIF) was established in 2007 and one of the main issues that was initially identified for its review was well handover documentation. NORSOK D-010 has one section (section 8.7.1) where the content of a well handover documentation package is outlined. Availability of, knowledge about and content of the well handover document were also main elements that were highlighted by the PSA in their well integrity survey as an area for improvement. This chapter describes WIF members recommendations for well handover documentation and is intended to function only as a guideline for the Norwegian oil and gas industry. 2. Background A survey completed by WIF members formed the basis for discussion and development of the guidance given in section 3. The body content of the handover documentation varied very little amongst the members, but the information was located and organized in different places. 3. Discussion The survey showed that the majority of information already included in the company specific well handover documents was common amongst the companies. All companies also had exceeded the NORSOK standard by including well barrier schematics. In the sections below the recommended guidelines for minimum content per focal area are listed. The format for how the documentation is structured has not been looked at, and is left to the discretion of each operator to organize the information.

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 12 a. Well Construction Data The handover should contain the following well construction information: Wellhead data with schematic Xmas tree data with schematic Casing program (depths, sizes) Casing and tubing data, including test pressures Cement data Fluid status, tubing and all annuli Wellhead pressure tests Tree pressure tests Completion component tests Perforating details Equipment details such as identification or serial numbers b. Well Diagrams The handover documentation should include the following two well schematics: Well barrier schematic with well barrier elements listed Completion schematic c. Handover Certificate The handover documentation should also include a handover certificate. The certificate should include actual status at handover on the following: Valve status

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 13 Pressure status Fluid status d. Operating Input Operating limitations for the well should also be included in the well handover documentation package. As a minimum the following information should be included: Tubing and annulus operating limit Test and acceptance criteria for all barrier elements (could be referenced to valid internal company documents) Deviations which are identified and valid for the well

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 14 CHAPTER 3 WELL BARRIER SCHEMATICS FOR THE OPERATIONAL PHASE 1. Introduction One of the Petroleum Safety Authority's (PSA) findings from the spring-2006 well-integrity audit was the requirement for the creation of well barrier schematics (WBS) for the operational-phase of each individual well on the Norwegian Continental Shelf (NCS). Each operating-company worked to fulfil this requirement, independently of other operators. As a whole the industry used the WBS's presented and well-barrier elements (WBE) defined in the NORSOK D-010 standard as a basis in developing their own WBS format. At the industryorganized, well-integrity workshop held in March 2007, the need for common, minimum guidelines for the subject WBS's was identified to help standardize this tool within the industry. The same workshop resulted in calls for establishing a well-integrity forum (WIF) to promote open and frequent discussion of well-integrity related issues amongst the NCS operators. One of the WIF's tasks was to further investigate the use of WBS amongst the operating companies and propose a minimum level of detail which should be included in each well specific WBS. This document summarizes the WIF's guideline of minimum data to be presented on WBS's of all NCS wells in the operational phase. These guidelines may re-state and/or add to existing requirements specified in the governmental regulations and NORSOK D-010 standard. The attached example WBS has been included for the purpose of illustrating the recommended guidelines 2. Background The task to establish a common WBS has been discussed and refined in WIF. The agreed guidelines of minimum data are listed below. 3. Guidelines of minimum data The following minimum data have been agreed upon and act as a guideline: 1. The formation strength should be indicated for formation within the barrier envelopes. 2. Reservoir(s) should be shown on the drawing. 3. Each barrier element in both barrier envelopes should be presented in a table along with its initial integrity-verification test results.

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 15 4. Depths should be shown relatively correct according to each barrier element on the drawing. 5. All casing and cement, including the surface casing, should be on the drawing and labelled with its size. 6. There should be separate fields for the following well information: Installation, well name, well type, well status, rev. no and date, Prepared by, Verified/Approved by. 7. Include a Note field for important well integrity information. 4. Discussion on minimum data 4.1 The formation strength should be indicated for formation within the barrier envelopes In all well designs, formation will be within the barrier envelopes and may therefore be exposed to reservoir and well pressures. It is important that it is understood which formations are inside the barrier envelopes and ensured that they are not exposed to pressures exceeding their strength. Exceeding the formation strength may result in leaks on the outside of casings and cement, outside the barrier envelopes. This is important for all well types; however, special attention should be given to injector wells. The strength of the formations which is within the barrier envelopes should therefore be indicated on the barrier drawing and should be considered when determining operational limits for the well. The formation strength can typically be based on physical measurements performed during drilling of the well, e.g. Formation Integrity Tests (FIT), Leak Off Tests (LOT) or Extended Leak Off Tests (XLOT). The indicated formation strength can also be based on tests done on core samples, results from downhole logs or correlations based on historical field data. The type of value used to indicate formation strength can differ in meaning and uncertainty (e.g. a FIT value has another meaning than a LOT value, a value derived from a downhole log has a higher uncertainty than a value based on tests on core samples), and it should therefore always be stated what the indicated formation strength is based on. The formation provides containment of reservoir fluids together with the well barrier elements which constitute the barrier envelopes, but the properties of formation is not tested, designed, monitored or known in the same manner as for a well barrier element, which have defined acceptance criteria. There is currently no common understanding of what well barrier element acceptance criteria should be used for formation to ensure that formation in a meaningful and adequate way can be treated and defined as well barrier element in the same manner as e.g. casing or production packers. Reservoir(s) should be shown on the drawing. The reservoir(s) should be shown on the drawing to be able to verify proper barriers. This will also ensure that any zone isolation requirements are fulfilled.

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 16 Each barrier element in both barrier envelopes should be presented in a table along with its initial integrity-verification test results By presenting each barrier element in the table, there will be no doubt regarding which elements are a part of the barrier envelope. In addition, this exercise will help the engineer to ensure the actual elements are qualified according to requirements and the ability to verify the integrity of each element. It is intended that the actual test results that verified the integrity is presented. For example pressure test and CBL are methods used. The actual results should be presented.- e.g. pressure test to 320 bar, FIT to 1,79 sg EMW, 100% bond at 3000 mmd. When the well is completed, it is important to keep data and status of the well barriers. By stating the actual integrity-verification method and test results for each element on the well barrier schematic, the status of the well is known and documented. This information is also important for the operational phase and later interventions and/or workovers. Depths to be shown relatively correct according to each barrier element on the drawing It is important that the drawing show the barrier elements at the correct depths relative to each other, and do not show e.g. that the production packer is set in cemented casing if the actual layout is otherwise. Likewise it is important to show the relative positioning of the reservoir(s) and the positioning of the cap rock relative to the cement and production packer. The relative positioning of the barrier elements is important in relation to integrity, robustness, and the ability to detect any leakages after initial installation and testing. For the same reason, it is also advised to show all packers, PBR s and similar equipment on the drawing. The drawing should be well specific and show/illustrate the actual layout of the well. All casing and cement, including the surface casing, should be on the drawing and labelled with its size For the same reason as above (4.4), it is important to show all casing sizes and the cement behind. This will give important information of the robustness of the well, and not lead to any misinterpretation of the design. There should be separate fields for the following well information: Installation, well name, well type, well status, rev. no and date, Prepared by, Verified/Approved by It is important that the well specific barrier schematic contain information about the validity of the drawing. Therefore installation name and/or field name should be clearly stated, and the name of the well.

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 17 To be able to understand the well barriers the "well type", if the well is an oil producer, water injector, gas injector etc, should also be stated. The status of the well, e.g. if the well is operational, shut in, temporary plugged for nippling etc should also be defined. This is important such that the validity phase of the well barrier schematic is clearly defined. Document and quality control is needed. Revision number, date, information about who has prepared, and who has verified or approved the schematic is therefore also needed. Include a Note field for important well integrity information Special well conditions that have changed the barrier envelope over time and other important well integrity information should be highlighted. This ensures any weaknesses are made aware of, and also shows the actual situation. References to where the integrity dispensations are located (e.g. number) should be made, with a short explaining text. The WBS should be updated when well conditions such as e.g. detected tubing/casing leaks, have changed the barrier envelope. Other important well integrity information that has not changed the barrier but still should be highlighted in the note field could e.g be leaks outside the barrier envelope. Attachment 1: Example of a well specific barrier schematic. Note that data have to be filled out where xx is stated for a real well.

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 18 WELL BARRIER SCHEMATIC KV PSV PUMV PLMV PWV X-mas tree Well information Installation: xxxxx Well no.: xx/xx-xx Well type: e.g.oil producer Well status: e.g. Operational Revision no. / Date: x xx.xx.xxxx Prepared: xxxxx Verified/Approved: xxxxx 18 5/8" csg 13 3/8" csg 9 5/8" csg SCSSV FG = xx s.g. FIT = xx s.g. FG = xx s.g. Well barrier elements Verification of barrier elements PRIMARY 7 liner cement xx bar with xx sg fluid Method: prognosed / measured TOC: xx mmd Method: volume control / logs e.g. CBL xx bonding at xx mmd 7 liner xx bar with xx sg fluid 7 liner hanger packer xx bar with xx sg fluid 9 5/8 casing between xx bar with xx sg fluid liner hanger packer and production packer Production packer xx bar with xx sg fluid Production tubing xx bar with xx sg fluid SCSSV Inflow test to xx bar SECONDARY 9 5/8 casing cement FIT to xx sg EMW. Method: prognosed / measured TOC: xx mmd above prod.packer / csg.shoe. Method: volume control / logs e.g. CBL xx bonding at xx mmd 9 5/8 casing xx bar with xx sg fluid 9 5/8 casing hanger xx bar with xx sg fluid with seal assembly Wellhead / annulus xx bar with xx sg fluid access valve Tubing hanger with xx bar with xx sg fluid seals X-mas tree valves xx bar with xx sg fluid 7" liner Reference / Disp. no. well integrity issues N/A Comments / Notes: Logo

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 19 CHAPTER 4 WELL INTEGRITY WELL CATEGORIZATION 1. Objective In response to heightened industry and regulatory interest, WIF developed a system of classifying a well based on its integrity status. Operators can benefit from this categorization system as a method of ranking well integrity within its operations, whereas the PSA will be able to use it to summarize well integrity across the entire NCS. A common categorization system will also promote a level of consistency amongst the various operators when evaluating the integrity of their wells. This guideline presents the resultant categories, summarizes the basis of each one and goes further in that it provides examples in an effort to promote a common understanding of each category for the end user. The system is intended for categorisation of all wells types which are in operation, shut in, suspended or temporarily abandoned. Wells which are under construction or permanently plugged and abandoned are not covered by this guideline. Defining acceptance criteria is outside the scope of this guideline, and is left to the discretion of the individual operators.

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 20 2. Abbreviations & Definitions Abbreviations ASCSSV ASCV ASV DHIV DHSV DMF ESD GLV KPI NCS Norsok Norwegian Oil and Gas PSA RNNP RNNS SCSSV TRSCSSV WBE WIF WIV WRSCSSV Annulus Surface Controlled Sub-Surface Safety Valve - see also ASV Annulus Safety Surface Controlled Valve Annulus Safety Valve - see also ASCSSV Downhole Injection Valve - see also WIV Downhole Safety Valve Drilling Manager Forum Emergency Shutdown Gas Lift Valve Key Performance Indicator Norwegian Continental Shelf Norsk Sokkels Konkurranseposisjon Norwegian Oil and Gas Association Petroleum Safety Authority Risikonivå i norsk petrolumsvirksomhet (Risk level in Norwegian petroleum activity) - see also RNNS Risikonivå på norsk sokkel (Risk level on Norwegian Shelf) - see also RNNP Surface Controlled Sub-Surface Safety Valve Tubing Retrievable Surface Controlled Sub-Surface Safety Valve Well Barrier Element Well Integrity Forum Water Injection Valve - see also DHIV Wireline Retrievable Surface Controlled Sub-Surface Safety Valve Definition of terms Leak to surface - Uncontrolled leak of fluids either to air, sea or seabed

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 21 3. Background Since the inaugural attempt to incorporate a NCS well-integrity summary in the 2006 RNNS report, the PSA has expressed interest for the Norwegian oil industry to develop a KPI system which would benefit operators and authorities alike. This effort was one of the initial tasks adopted by the WIF upon being established in the summer of 2007 under the auspices of DMF/Norwegian Oil and Gas. Work began with an overall review of the current practices of WIF-member companies in ranking the integrity of their wells. Systems varied from operator to operator in terms of stage of development and level of complexity. Some, having adopted corporate programs which had been pushed out globally, suggested another system would have limited benefit; however, most had developed or were developing local programs and believed that a common categorization process would be useful. It was decided that WIF should work on a Norwegian oil-industry recommendation that would focus on wells in the production phase. Furthermore; it should be kept simple and a matrix of 3-4 "traffic lights" would lend itself to this simplicity. With feedback from DMF and PSA, WIF was able to propose the 4-category, traffic-light system based on double-barrier principles. A pilot project was run in 2008 during which various operators applied the categorization to a sample of their wells. Based on encouraging pilot results, WIF proposed the system for use in the PSA's 2008 RNNP report. The WIF guideline for the well-integrity categorization was purposely held off until 2009 in order to be optimized with experiences from the previous year's RNNP and the 2009 Well Integrity Norwegian Oil and Gas workshop.

No.: 117 Established: 01.10.08 Revision no: 4 Date revised: 06.06.2011 Page: 22 4. Philosophy Double Barriers The well-integrity categorization is based on compliance to the barrier policy outlined in the regulations and the Norsok D-010 Standard. Chapter 4 of the standard states There shall be two well barriers available during all well activities and operations, including suspended or abandoned wells, where a pressure differential exists that may cause uncontrolled outflow from the borehole/well to the external environment. It should be noted that Norsok only requires one barrier against cross flow in the wellbore between formations. Risk The barrier policy was established as a means of reducing the hazard of an uncontrolled release from a well. As such the categorization has an association with risk; however, it is not absolute. The categorization system does not replace risk assessments. For instance, two wells with only one remaining barrier can pose different levels of risk if one is a high-rate gas well on a manned platform whereas the second is a subsea water injector. The operator should consider a further in-depth risk assessment process for wells that are ranked high. Traffic Lights The four-category system utilizes a green/yellow/orange/red traffic-light, colour-coded system for visualization purposes which is similar to many operator and regulatory ranking systems. Green and yellow are acceptable according to standards and in compliance with the two-barrier principle, with yellow only serving to highlight some well-integrity anomalies. Orange and red spotlight non-compliant wells with well-integrity problems which usually will be further diagnosed, evaluated and risk assessed for appropriate follow-up action. Red is used to highlight wells which in addition to failure of one barrier have considerable degradation or failure of the second barrier. Current State The categorization should reflect the current condition and status of the well. Ranking of a well could change if it is put on gas lift, secured with a plug, shut-in, repaired, etc. The PSA's RNNP report usually requires the state of an operator's wells as of a specific date near the end of the year; however, the well condition could change anytime throughout the year. Operating companies should strive to keep their categorization up-to-date.