Lessons Learned: Well Control Incident, Shoe Bond
Inadequate cement shoe bond leading to gas influx.
After cementing 9 ⅞” liner on an appraisal well, a cement evaluation log was performed, confirming the need for a remedial shoe bond job (next section was anticipated to have a narrow mud weight window).
After the remedial job, operations were carried on with a Formation Integrity Test (FIT).
At this point, due to some doubts on the sealing effectiveness and possible connection to a gas layer behind the shoe, an extended flow check was carried out detecting a gas influx. The well was shut-in and the influx was controlled using the drillers method.
What happened?
A 9 ⅞” casing was set and cemented at 4800m.
Inflow test of the shoe track was successful.
The shoe track and 5m of new formation were drilled out and A FIT is performed below the shoe without any issue.
Before resuming drilling, an extended flowcheck was performed and a gain of 4.5bbls recorded. Well was shut in and pressure monitored – stabilization at SICP 230psi and SIDP 250psi.
Drillers method was engaged – reducing safety margin as losses were experienced – gas was evacuated (9% behind MGS). Proceeded to 2nd circulation with 1.65SG Kill Mud.
Communication to gas layer behind 9 ⅞” liner due to poor cement integrity behind liner. Disturbed during FIT.
What went wrong?
Communication to gas layer behind 9 ⅞” liner due to poor cement integrity behind liner. Disturbed during FIT.
Corrective actions and recommendations
Capture and transfer experience for new wells in surrounding area.
Lesson Sharing, IOGP Well Control Incident, IOGP WCI Lesson Sharing 24-7, “Inadequate cement shoe bond leading to gas influx.”
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