IOGP Well Control Incident Lesson Sharing
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Hydrocarbon flow during gauge change-out


During snubbing operations personnel attempted to replace a spool wing valve pressure gauge. Once containment was broken, hydrocarbons flowed from the well for ~ 15 minutes. Please consider the following questions in your review of this incident:

  1. How does your company verify, record and track barrier status throughout well operations?
  2. How does your company control work tasks during well operations and what is the minimum threshold for management of change?
  3. Can you identify areas in your well operations where common field practices have led to the normalization of risks and how can you prevent this in the future?
  4. Which Human Factors (HFs) were an issue here and how does your company strive to protect itself from these HFs?
  5. What information should be recorded within a handover? When is it updated? Who updates it? Who issues it? When is it issued and to whom?

IOGP Wells Expert Committee/Well Control Incident Subcommittee believes that this incident description contains sufficient lessons to be shared with the industry. We further encourage the recipients of this mail to share it further within their organization.


The snubbing unit was rigged up and the pump was lined up and ready to pump 10ppg brine as the working fluid.

Prior to running in hole, as there was no tubing in the well, the supervisor asked two hands to check the pressure in the well, which could be done via a gauge on the tubing spool wing valves.

The crew was experienced and, upon arrival at a location, routinely changed out the pressure gauge for one with a more suitable pressure range for the operation and a preferred type and model. In this incident, changing out the gauge, which required breaking containment, was not identified as part of the work scope to check the well pressure.

The crew manipulated the valves - one turn open / one turn close with resistance - in an attempt to validate closure and proceeded to remove the gauge. At this point, grease flowed out of the wing, followed by hydrocarbons. Hydrocarbons flowed for ~15 minutes until the crew started pumping brine. When the brine was pumped, the hydrocarbon flow was displaced by the brine and the flow pressure was reduced.

A junk shot was pumped into the wing approximately 7 hours after the start of the incident, shutting off flow completely. The team then pumped 16ppg OBM to fully kill the well. A packer was set and both side outlet valves were replaced fully securing the well.

Post incident investigation concluded that the side outlet valves were blocked with debris from prior operations and were prevented from closing fully. It is believed that frac sand formed the blockage.

What Went Wrong?:

The planned scope of work, i.e. taking well pressures, did not account for the possibility of breaking containment to change the pressure gauge. As a consequence the verification of barriers was not completed prior to breaking containment.

A written and approved procedure to change the gauge was not used, instead relying on experience and field practice. The learned practice did not incorporate a robust procedure for confirming valve closure, e.g. fully opening and counting turns.

The well handover process between work teams was not formalised and was reliant on communication of well status between teams. Prior maintenance conducted on the side outlet valves was not effectively identified and highlighted.

The crew assumed the valves started in the closed position due to standard field practices and interpreted the evidence of gauge reading and resistance on closing to support their assumptions.

Corrective Actions and Recommendations:

  • Develop structured well handover process with focus on barrier status.
  • Well barrier diagrams, including barrier acceptance criteria, to be included in well program for each stage of operation.
  • Verify that onsite supervisorsí handovers address barrier status.
  • Utilise barrier diagrams on location to drive understanding of barriers, status and validation requirements as part of the start work requirements. Work will not start without complete barrier validation and documented plan for the planned operation.
  • Engineering teams incorporate barrier status discussions during scheduled field supervisor calls.
  • Team leads to assure expectations of barrier ownership understood during field visits.


safety alert number: 337
IOGP Well Control Incident Lesson Sharing http://safetyzone.iogp.org/

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