Conventional gas lift wells are characterized by a large volume of gas in the annulus under high pressure. In the event of accidental flow, this gas volume can increase the overall risk to facilities with regard to fire or explosions. Annular safety valves are utilized to reduce this risk.
The Norwegian petroleum regulations (Regulations relating to health, environment and safety in the petroleum activities 2002-2004) stipulated detailed requirements for use of these types of valves in well completions with gas lift in Section 53 of the Facilities Regulations relating to completion and controlled well flow.
Recent analyses conducted by certain oil companies showed, however, that the total risk associated with completion and maintenance of gas lift wells with annular safety valves can be affected negatively under specific conditions.
The purpose of the audit activity was therefore to
The audit resulted in an amendment to the regulations which entered into force on 1 January 2005 and which, under certain circumstances, opens the door for alternative technical, operational and organizational solutions instead of using annular safety valves.
The amendment is in line with the third and most recent revision of NORSOK standard D-010 "Well integrity in drilling and well operations", which entails that the necessity for annulus safety valves can now be assessed from situation to situation in relation to the following aspects:
General barrier requirements in accordance with Section 47 of the Facilities Regulations relating to well barriers. An annular safety valve is assigned a function as a primary barrier element against the reservoir (and simultaneously as a safety valve against the gas volume in the annulus) if the well is planned without other qualified barrier elements between the annular safety valve.
The risk of a major accident, cf. Section 6 of the Management Regulations relating to acceptance criteria for major accident risk and environmental risk, as well as Section 14 of the Management Regulations relating to analysis of major accident risk.
The risk level influenced by the annular safety valve, compared with alternative solutions over the field life, cf. Section 1 of the Management Regulations relating to risk reduction, as well as Section 15 relating to quantitative risk analyses and emergency preparedness analyses.
Based on these observations and experiences, the PSA is considering intensifying its efforts with regard to well safety in gas lift wells, particularly for facilities with dedicated wellhead decks, on multi-purpose facilities, and on fields with high reservoir and well pressure.
The PSA will also follow up the operator's requirements in relation to testing of gas lift valves and use of gas lift valves as qualified barrier elements.
Contact person i the Petroleum Safety Authority
Claas van der Zwaag