TABLE OF CONTENTS 1 Acknowledgements ...................................................................................................................... 11 2 Abstract ......................................................................................................................................... 12 3 Introduction ................................................................................................................................... 13 4 Requirements for plug and abandonment operations ............................................................... 16 5 Units to perform Plug and Abandonment ...................................................................................19 5.1 Category A, Category B and Category C ............................................................................................................ 19 5.2 Riserless Light Well Intervention (RLWI) ............................................................................................................ 20 5.2.1 Wireline operation from a RLWI vessel ................................................................................................... 20 5.2.2 Challenges when using RLWI vessels compared with use of semi-submersible rigs ............................ 21 6 Plug and Abandonment operation .............................................................................................. 22 6.1 Plug and Abandonment-Existing practice ........................................................................................................... 22 6.1.1 Connect to XMT ....................................................................................................................................... 22 6.1.2 Kill and secure well .................................................................................................................................. 22 6.1.3 Install tubing hanger plugs ....................................................................................................................... 23 6.1.4 Handling of subsea trees in P&A operations ........................................................................................... 23 6.1.5 Run BOP and Marine Riser ..................................................................................................................... 24 6.1.6 Pull tubing hanger and tubing .................................................................................................................. 24 6.1.7 Run cement log ........................................................................................................................................ 25 6.1.8 Establish well barriers and perform verification ....................................................................................... 26 6.1.9 Establish open hole to surface barrier ..................................................................................................... 26 6.1.10 Cut and retrieve wellhead ........................................................................................................................ 26 6.2 Overview over P&A operations and experience from RLWI vessel ................................................................... 27 6.3 RLWI experience from plug and abandonment operations ................................................................................ 28 6.3.1 First attempt to perform P&A and establish cement barrier from a RLWI vessel ................................... 28 6.3.2 Temporary plug and abandonment operation performed by RLWI vessel ............................................. 29 7 Technology Challenges................................................................................................................ 30 8 Logging challenges in P&A operations ...................................................................................... 31 8.1 Cement bond logging through multiple casing strings ........................................................................................ 31 8.1.1 The big picture regarding logging tools and log response ...................................................................... 31 8.1.2 Status regarding cement bond logging through multiple casing strings ................................................. 33 8.2 Log cement behind casing with tubing partly retrieved ....................................................................................... 33 8.2.1 Comments regarding log cement behind casing with tubing partly retrieved ......................................... 33 8.3 Identify control lines behind the tubing ................................................................................................................ 34 8.3.1 Challenges with control lines ................................................................................................................... 34 8.3.2 How to identify the control lines ............................................................................................................... 34 8.3.3 Ultrasonic logging tool .............................................................................................................................. 35 8.3.4 X-ray ......................................................................................................................................................... 36 8.3.5 Comments regarding identification of control lines.................................................................................. 36 9 Technology for cutting of tubing and control lines ...................................................................37 9.1 How to cut tubing and control lines simultaneously ............................................................................................ 37 9.1.1 Baker Hughes mechanical power cutter .................................................................................................. 37 9.1.2 7 inch Downhole Electric Cutting Tool ..................................................................................................... 38 9.2 Remove only necessary length of control lines ................................................................................................... 38 9.3 Retrieve tubing, break and isolate control lines .................................................................................................. 39 9.4 Spiral cutting of the tubing and control lines ....................................................................................................... 39 9.5 In situ control lined ............................................................................................................................................... 40 9.6 Cutting sub for control lines ................................................................................................................................. 40 9.7 Comments about the methods ............................................................................................................................ 41 10 Different approaches for removing tubing .................................................................................42 10.1 Technical solutions and new technologies to retrieve tubing and establish barriers with RLWI vessel ............ 42 10.1.1 Operating capacities and limitations ........................................................................................................ 42 10.1.2 Additional equipment needed compared with a standard RLWI operation ............................................. 42 10.1.3 Subsea Shutoff Device ............................................................................................................................ 43 10.1.4 Volume Control System ........................................................................................................................... 45 10.1.5 Unseat tubing hanger with Jack mechanism ........................................................................................... 47 10.1.6 Tubing Hanger Running and Orientation Tool ......................................................................................... 48 10.1.7 Hydraulic power unit Subsea ................................................................................................................... 48 10.1.8 Pipe handling system ............................................................................................................................... 49 10.1.9 Retrieve tubing to surface or place at seabed ......................................................................................... 50 10.1.10 Risk register from Hazop ............................................................................................................... 50 10.1.11 Comments regarding retrieving tubing to surface ......................................................................... 50 10.2 New approaches for removing tubing ................................................................................................................. 51 10.2.1 Push tubing down by crushing tubing ...................................................................................................... 51 10.2.2 Use of chemicals to remove the tubing ................................................................................................... 52 10.2.3 Remove tubing by melting ....................................................................................................................... 52 10.3 Summary.............................................................................................................................................................