§ 54 Christmas tree and wellhead
Christmas trees and wellheads shall be designed such that prudent well control can be performed through recovery, workover and well intervention.
The christmas tree shall have at least two main valves, and at least one of them shall be automatic.
In the case of hydrocarbon flow in the annulus, the closest outer annulus shall be pressure-monitored.
Section last changed: 01 January 2014
The equipment as mentioned in the first subsection, also encompasses casing hangers and annular preventers. To fulfil the requirements in the section, the standards NORSOK D-010 Chapters 8.7.2, 9 and Annex C, NORSOK U-001, ISO 10423 and ISO 13628 should be used, with the following additions:
- In order to fulfill the requirement in the first subsection, all annuli on surface-completed wells and the nearest annulus to flow pipes for production or injection in subsea-completed wells should have pressure monitoring,
- The main valves as mentioned in the second subsection, should be integrated in, or mounted directly on, the christmas tree. It should be possible to close inlets and outlets in the christmas tree that can be subjected to well pressure in at least two independent ways. Injection points should have check valves as close to the injection point as possible,
- It should be possible to isolate wellhead christmas trees to avoid unintended closing of valves during well intervention,
- The closing time for valves in the main barrel and side outlets of the seabed christmas trees should be assessed in relation to the barrier function of the valves. This evaluation should include necessary closing time in relation to the risk-reducing function and the location of the valve.