TL;DR
A leaking wellhead gate valve seat is a barrier integrity failure. Test the valve per the pressure test procedure and escalate to the well control team if the test fails.
What you might see
- process gas or liquid passing across a closed gate valve
- pressure bleeding down downstream of a closed valve
- valve failing the seat test
- visible seepage at the valve body drain or vent
Likely causes
Seat or gate erosion from produced fluids containing sand or scale
Stem packing leak allowing wellbore fluid bypass through the bonnet
Gate not fully seated due to debris on the seating surface
Body or bonnet seal degradation from exposure to H2S or CO2
Required tools
- Calibrated test pressure gauge
- LOTO kit (for stem packing work only)
- Torque wrench (for packing gland)
- Gas detector (H2S and hydrocarbon)
Safety first
- Wellhead valves control live wellbore pressure. All valve testing must be performed with well control authorization and under a written test plan.
- H2S may be present at wellhead valve vent and drain ports. Wear supplied-air respirator and use calibrated H2S monitors in the wellhead area.
- Never apply excess torque to a wellhead packing gland to stop a leak. Excessive torque can damage the stem and cause a sudden release.
Procedure
- 1
Confirm the valve is in the fully closed position. Verify the handwheel or actuator is at the hard stop.
Warning: Wellhead valves control live wellbore pressure. Do not open or close any valve without well control authorization and a pressure test plan. - 2
Monitor the downstream pressure gauge for pressure bleed-up after a valve closure. Bleed-up indicates seat leakage.[1]
- 3
Perform a seat test per the general pressure test procedure for the valve rating. Apply test pressure and hold for the required duration.[1]
- 4
Check the stem packing area for seepage. Re-torque the packing gland to the specified value if minor weeping is observed.
- 5
If the seat test fails, record the leak rate and notify the well control engineer.
- 6
Do not attempt field repair of a Cameron wellhead valve seat. Seat reconditioning requires valve removal and return to a certified workshop.
- 7
Log the test result in the wellhead integrity management system.
Sources
Cameron (SLB) Cameron Type FC / FLS-R Wellhead / Christmas Tree general technical documentation, Cameron (SLB)
Cameron Type FC / FLS-R wellhead general gate valve seat testing and integrity procedures (general)
More guides for Cameron (SLB) Cameron Type FC / FLS-R
How to diagnose actuator failure on a Cameron Type FC / FLS-R wellhead valve
Actuator failure on a wellhead valve can prevent safe isolation. Check the hydraulic or pneumatic supply, then the solenoid and position feedback before declaring the actuator failed.
How to diagnose a casing head gasket leak on a Cameron Type FC / FLS-R wellhead
A casing head gasket leak is a surface well control issue. Test the flange, confirm the leak rate, and notify the well control team before any repair.
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