Hydrocarbon release from a wellhead swab valve

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Alert ID: 
Description of Task: 

Hydrocarbon release from a wellhead swab valve

The incident occurred on a naturally producing well with a typical flowing tubing head pressure of 40 bar and a closed in tubing head pressure of circa 100 bar. The well underwent a routine PMR and repair of the Swab valve in Oct 2013 and returned to service. 4 months later, in Feb 2014, a weep was identified from the bonnet of the swab valve and the decision was taken to manage this via the weeps and seeps procedure.

In March 2014 the platform suffered a shutdown due to a power outage. During the restart of the process the well in question was reset. At this point the weep on the swab bonnet increased to a leak. This was observed by a member of the production department and reported to control room. The platform GPA was initiated and the leak was isolated.

Lessons Identified: 

  • Spare equipment/ parts/ components held within asset Toolboxes for use during maintenance tasks were not properly labelled and identified to avoid wrong selection of gaskets
  • The specific work pack mobilised for the PMR and repair of the Swab valve did not include any replacement bonnet gasket
  • Breakdown in communication led to no formal intervention for flowing the well with a known weep. Deviation was not issued ordering the well to be shut-in and weep repaired
  • Lack of awareness of risks associated with inserting the incorrect  bonnet gasket
  • Weeps and seeps procedure not robust enough to have directed the site to shut in the well


Ensure that all spare gaskets are labelled and easily identifiable to avoid wrong selection of gaskets

Ensure any weeps and seeps procedure is robust enough to guarantee that personnel with the  necessary expertise are involved in the decision to manage any weep/seep via the procedure or to isolate and repair immediately

Information source: 
Contact Details: 
Andrew Howard, Hydrocarbon Release Prevention Focal Point, Talisman Sinopec Energy UK
Specific Equipment: 

Wellhead swab valve

Incident consequence: 
Hydrocarbon release
Production operations
Fixed Installation
Cause of accident or incident: 
Uncontrolled release of a flammable gas or liquid