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/

Disclaimer

Whilst every effort has been made to ensure the accuracy of the information contained in this publication, neither the IOGP nor any of its members past present or future warrants its accuracy or will, regardless of its or their negligence, assume liability for any foreseeable or unforeseeable use made thereof, which liability is hereby excluded. Consequently, such use is at the recipient's own risk on the basis that any use by the recipient constitutes agreement to the terms of this disclaimer. The recipient is obliged to inform any subsequent recipient of such terms.
This document may provide guidance supplemental to the requirements of local legislation. Nothing herein, however, is intended to replace, amend, supersede or otherwise depart from such requirements. In the event of any conflict or contradiction between the provisions of this document and local legislation, applicable laws shall prevail.