Is it necessary to install a downhole safety valve in a subsea ... - NTNU

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Is it necessary to install a downhole safety valve in a subsea oil/gas well? The need for an experienced HAZOP chairman is crucial. It is important that the chairman is familiar with the type of work being analyzed and that sufficient authority is achieved to control the discussion. During the team discussion the chairman should act as a catalyst and guide the team in posing the appropriate type of questions. Finally the leader should draw the conclusions from the discussion and propose the appropriate entry in the record sheet. YES NO NO Select a procedure Have all the relevant guide-words for this procedure been considered? NO Select a relevant guide-word not previously considered Are there any causes for this deviation not discussed and recorded YES Record the new cause Are the associated consequences of any significance? YES Record the consequences Record any safeguards identified Having regard to the consequences and safeguards, is an action necessary? YES Record the agreed action Figure 6-2 Flow chart of a HAZOP examination procedure (based on [2]) Diploma thesis, NTNU 2002 NO 44
Is it necessary to install a downhole safety valve in a subsea oil/gas well? 6.2.3 HAZOP of the BOP handling procedure In an overall risk assessment the identification of hazards and hazardous events are important. The implementation of a procedure HAZOP on a workover will help identifying the hazards and its potential consequences. A complete HAZOP of a workover is to comprehensive for this thesis and the competence of the author. In this study only the handling of the Blowout preventer (BOP) is considered. The HAZOP of the BOP handling procedure provided in this thesis has not been subject to a group discussion and a HAZOP team. The outcome will be fully dependent on the authors understanding of the problem. Important issues might have been left out and the weighing of criticality may not have been done to the satisfaction of all readers. In the traditional HAZOP analysis the guide-words; NO, MORE, LESS, AS WELL AS, etc. are used. In a procedure HAZOP these words are, from some point of views, not as well suited. Instead a set of guide-words in interest for the specific analysis are developed for the specific procedure. The author experimented with the use of such guide-words in the procedure HAZOP without success. The traditional guide-words are of a general character and easier to apply to the different procedures in the study of BOP handling. An understanding of why this guide-word is applied is given for each of the steps in the “causes”-column of the HAZOPsheet. The need for more specific guide-words was therefore neglected. Traditional guidewords are also more common and easier to understand. As a result the traditional guide-words are applied in this thesis. The guide-words used and their meaning is presented in appendix E. 6.2.4 The BOP handling procedure In this chapter a Blowout preventer (BOP) handling procedure is described. This procedure will be analysed systematically as a part of a procedure HAZOP. The procedure is only used to illustrate the employment of a HAZOP study and is therefore reduced. If a full HAZOP study of the BOP handling procedure is wanted a more extensive description of each step should be done. 1. The BOP is tested on a hub 2. The AX-seal ring on the BOP is checked 3. The BOP is moved by forklift truck over the hole on the cellar deck. 4. A riser pipe is lifted off the pipe rack with the pipe handling equipment 5. The riser pipe is lowered through the drilling deck and screwed on to the top of the BOP by an iron roughneck. 6. The BOP is lifted off the fork truck by a riser elevator, lowered and hung at the drilling deck. 7. The roughneck screws a new riser pipe on and the riser elevator is used to lower the riser with the BOP attached. 8. This procedure is repeated until the BOP is lowered to the seabed. 9. The guideline wires are tightened to find the right position for the BOP 10. The BOP is connected to the wellhead 11. The BOP is pressure tested for leakage in the AX-seal 12. Workover is performed through BOP 13. BOP is disconnected from wellhead 14. The BOP is raised with the riser elevator 15. Guidelines are loosened to move BOP away from well Diploma thesis, NTNU 2002 45
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Page 69 and 70: APPENDIX A A1 Subsea production sys
Page 71 and 72: A1.3 Well completion A1.3.1 Tubing
Page 73 and 74: A1.5.2 Guidelineless system Several
Page 75 and 76: Appendix B In this appendix a figur
Page 77 and 78: Appendix C Fault trees constructed
Page 79 and 80: Production Wing valve ITL WV Produc
Page 81 and 82: Component: Production Packer Failur
Page 83 and 84: Reliability data dossier Component:
Page 85 and 86: Component: Production wing valve Fa
Page 87 and 88: Component: Crossover line Failure r
Page 89: Appendix F The guide-words used in
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Is it necessary to install a downhole safety valve in a subsea ... - NTNU

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