IOGP Well Control Incident Lesson Sharing

Wellbore flow observed while setting emergency casing slips

A land-based Drilling Rig was unable to run the casing string to the planned setting depth, requiring the casing string to be cemented in-place and the emergency casing slips to be set.

Following the completion of the cement job (and required wait-on-cement time), the BOP stack was lifted and the emergency casing slips were installed. At this point, flow was observed through the side-outlet valves. The BOP stack was reinstalled and the well was shut in.

The 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 team were unable to run the casing to the planned setting depth which resulted in the need to utilise the emergency slips to hang off the casing after the cement job was completed.

  • The cement job was completed successfully and the team waited for cement to reach adequate compressive strength before moving forward with installation of the emergency slip assembly.
    • Free point and bond log results prior to the cement job indicated that the casing was stuck and potentially packed off at 2000'.
  • Before breaking the BOP/Wellhead connection, a 90-minute flow check was performed and the well remained static.
    • Emergency slip installation required access to the wellhead via disconnecting and lifting the BOP stack. The slips are then installed, the casing cut and dressed off and the seal assembly is installed.
  • The BOP stack connection was broken, and the BOP stack was lifted and secured via the stack winches mounted beneath the rig floor.
  • After installing the slips but prior to cutting the casing and installing the pack off seal assembly, flow observed through the open side outlet valves. The side outlets had been left open to monitor for any potential flow.
  • The BOP stack was reinstalled per contingency plan and the well was shut in.
  • After shut-in, the well was monitored for 3 hrs and remained at 0 psi. Two separate gauges were installed to confirm that this was a correct reading.

What Went Wrong?:

The emergency casing slips installation required lifting BOP to access the wellhead.

Underlying cause - Design/Planning.

Corrective Actions and Recommendations:

The fluid column was sufficiently adequate to prevent sustained flow and it is believed that the observed flow was as a result of a migrating bubble.

The risk mitigations including kill weight mud in the hole and successfully implementing the detailed contingency plan of reinstalling the BOP stack in the event of flow prevented the incident from escalating.

safety alert number: 343
IOGP Well Control Incident Lesson Sharing


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