An Introduction to Well Integrity Rev 0, 04 December 2012 0 Preface This document has been prepared as a joint project between members of the Norwegian Oil and Gas Association's Well Integrity Forum (WIF) and professors at NTNU and UiS. The intention with the document is to provide a document that can be used in educating personnel in well integrity and especially students at the universities. Authors of this document have been: Hans-Emil Bensnes Torbergsen, Eni Norge Hilde Brandanger Haga, Statoil Sigbjørn Sangesland, NTNU Bernt Sigve Aadnøy, UiS Jan Sæby, Shell Ståle Johnsen, Total Marvin Rausand, NTNU Mary Ann Lundeteigen NTNU 0 04.12.12 Original document Revision Date of issue Reason for Issue 1 Index Preface ................................................................................................................................................ 1 List of Abbreviations ................................................................................................................................ 6 List of figures ............................................................................................................................................ 1 List of Tables ............................................................................................................................................ 4 1. What is well integrity? (Well integrity – concepts and terminology) ........................................... 5 2. Background and History ................................................................................................................... 8 2.1 What can go wrong in wells? ................................................................................................. 9 2.2 How likely is loss of well integrity? ...................................................................................... 10 2.3 What are the consequences of loss of well integrity? ........................................................ 11 2.4 Some cases of loss of well integrity ..................................................................................... 12 2.4.1 Case 1: Failure of surface casing and drop of wellhead.............................................. 12 2.4.2 Case 2: Failure of production casing hanger ............................................................... 15 2.4.3 Case 3: Loss of wellbore .............................................................................................. 17 2.4.4 Case 4: Gas leaks in tubing strings .............................................................................. 20 2.4.5 Case 5: Production casing failure ............................................................................... 25 2.4.6 Case 6: Well failure .................................................................................................... 26 3. Well Construction and Field Development .................................................................................... 29 3.1 Well Types and Well Life Cycle ............................................................................................ 29 3.2 Subsea drilling ..................................................................................................................... 29 3.3 Platform drilling .................................................................................................................. 35 3.4 Subsea Well Completion ..................................................................................................... 35 3.4.1 Types of X-mas trees for subsea wells ........................................................................ 36 3.5 Surface well completion ...................................................................................................... 40 4. Well Barriers – definitions, classification, and requirements.................................................. 45 4.1 Key concepts and definitions ............................................................................................... 45 2 4.2 Well Barrier Requirements .................................................................................................. 46 4.3 Well Barrier Functions ......................................................................................................... 47 4.4 Well barrier schematics and diagrams ................................................................................ 49 4.4.1 Well barrier schematics .............................................................................................. 50 4.4.2 Well barrier diagrams ................................................................................................. 51 4.5 Reliability analysis and methods ......................................................................................... 53 4.5.1 Reliability analysis of well barriers .......................................................................... 53 4.5.2 Analysis steps .............................................................................................................. 53 4.6 Identification of barrier functions ....................................................................................... 55 4.7 Failure and failure analysis ................................................................................................ 56 4.7.1 Key terms and definitions ........................................................................................... 56 4.7.2 Classification of failure modes .................................................................................... 58 4.8 FMECA ................................................................................................................................. 60 4.8.1 FMECA procedure ....................................................................................................... 61 4.9 Fault tree analysis ................................................................................................................ 68 4.9.1 Fault tree programs .................................................................................................... 70 4.9.2 Fault tree construction ............................................................................................... 70 4.9.3 Fault tree pros and cons ............................................................................................. 74 4.9.4 Qualitative analysis of the fault tree........................................................................... 74 4.9.5 Failure rate, mean time to failure, and survival probability ....................................... 75 4.9.6 Well barrier performance data ................................................................................... 76 4.9.7 Quantitative analysis .................................................................................................. 77 5. Technical well barriers ................................................................................................................... 80 5.1 Well barrier philosophy ....................................................................................................... 80 5.1.1 Fail-safe functions: ...................................................................................................... 80 5.1.2 Safety systems ............................................................................................................ 81 5.1.3 Fire resistance ............................................................................................................. 81 3 5.1.4 Well barrier schematics .............................................................................................. 82 5.1.5 Drilling phase .............................................................................................................. 87 5.1.6 Completion phase ....................................................................................................... 89 5.1.7 Production phase ........................................................................................................ 91 5.1.8 Intervention phase ...................................................................................................... 93 5.1.9 P&A phase ................................................................................................................... 95 5.2 Barrier design, construction and qualification of barriers for life cycle ........................... 97 5.2.1 MWDP or MSDP .......................................................................................................... 97 5.3 Description of typical barrier elements and important qualification issues ...................... 98 5.3.1 Formation ................................................................................................................... 98 5.3.2 Casing Cement .......................................................................................................... 101 5.3.3 Casing Cement Plug .................................................................................................. 103 5.3.4. Casing/Tubing ........................................................................................................... 104 5.3.5. Production packer ..................................................................................................... 106 5.3.6. DHSV ......................................................................................................................... 107 5.3.7. CIV ............................................................................................................................