Inadequate cement shoe bond leading to gas influx
IOGP Well Control Incident Lesson Sharing #24-7
After cementing 9 7/8” 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.
9 7/8” 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.
What Went Wrong?:
Communication to gas layer behind 9 7/8” ; 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.
safety alert number: 369
IOGP Well Control Incident Lesson Sharing http://safetyzone.iogp.org/
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