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

Recommendations

Info

Is it necessary to install a downhole safety valve in a subsea oil/gas well? Table 3-2 Safety integrity levels for safety functions operating on demand or in a continuous demand mode from IEC 61508-1, Table 2 and 3)[28] Safety Integrity Level (SIL) Demand Mode of Operation (average probability of failure to perform its design function on demand –PFD) Continuous / High Demand Mode of Operation (probability of a dangerous failure per hour) 4 ≥ 10 -5 to < 10 -4 ≥ 10 -9 to < 10 -8 3 ≥ 10 -4 to < 10 -3 ≥ 10 -8 to < 10 -7 2 ≥ 10 -3 to < 10 -2 ≥ 10 -7 to < 10 -6 1 ≥ 10 -2 to < 10 -1 ≥ 10 -6 to < 10 -5 An extract of the minimum SIL requirements given in ref. [28] relating to the object of this thesis is presented in Table 3-3. The SIL requirement concerning the shut-in of the flow in a well (Wing valve, Master valve and DHSV) is set to 3. It is therefore reasonable to also require a SIL3 for a well without a DHSV. Table 3-3 Minimum SIL requirements - global safety functions, an extract [28] Safety function SIL Functional boundaries for given SIL requirement / comments Isolation of well; (shut in of one well) 3 The SIL requirement applies to the sub-function needed for isolation of one well, i.e: - ESD-node (wellhead control panel) - Wing valve (WV) and master valve (MV) including solenoide(s) and actuators - Downhole safety valve (DHSV) including solenoide(s) and actuator Diploma thesis, NTNU 2002 Ref. APP. A A.6 10
Is it necessary to install a downhole safety valve in a subsea oil/gas well? 4 Overall risk assessment Risk may be denoted by the probability for and the consequence of unwanted events. When discussing risk a focus on environmental damage, economic loss and the loss of human life are essential. These factors must be considered in all well life phases in an overall risk assessment. Hazard identification performs a basis for the assessment. The frequency and the related consequences are evaluated and employed to the problem in order to provide a solution or a documentation of the potential danger. The role of the downhole safety valve (DHSV) will be discussed in each of the well life phases. In this study the completion, production and workover phases will be the main focus. The DHSV is not present during the drilling phase; this phase is therefore excluded from the study. 4.1 Consequences The consequences related to the presence of a DHSV are equal to the ones of well without a DHSV. The DHSV is rather the cause of either an improvement or deterioration of the failure frequency. The consequences relating to incidents occurring in the different life phases of the well can be broken down as illustrated in Figure 4-1 to Figure 4-3. Consequences Human Economic Environmental Injured personnel Broken equipment Delayed operations Blowout + Leakages Lost objects Figure 4-1 Consequence breakdown structure of the installation of a subsea production well Lost production Consequences Economic Environmental Shut-in of well Blowout + leakages Figure 4-2 Consequence breakdown structure of normal production on a subsea production well Diploma thesis, NTNU 2002 11
Page 1 and 2: Is it necessary to install a downho
Page 19: Is it necessary to install a downho
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
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?