IOGP Well Control Incident Lesson Sharing

Kick taken while drilling in the production hole section resulting in well control incident.


While Drilling the 6 1/8” production hole section, an increase in flow - with pumps on - was observed (positive kick indicator). The rig crew spaced out the drill string, shutdown the pumps, and shut-in the well with the BOP’s annular preventer. After three hours, the Casing Pressure (CP) stabilized at 130 psi with no appreciable measurable surface pit volume increase. The rig team bumped the float and obtained a Shut-in Drill Pipe Pressure (SIDPP) of 190 psi. After discussion with the office, the rig team suspected trapped pressure from ballooning and bled off casing pressure from 130 psi to 100 psi. Despite the CP coming back to 130 psi in 33 seconds and without discussing with the office, the rig team bled pressure over three more cycles. Following each bleed cycle, the CP increased back to the starting pressure of 130psi. Still believing the pressure was from ballooning, the rig team decided to fully open the choke and monitor flow on the trip tank. After bleeding back 14 bbls they decided to shut-in again. The wellsite team re-bumped the float and calculated a different SIDPP of 250psi. The rig team killed the well with the Driller’s method using the Kill Weight Mud determined from the “second” SIDPP; however they did not achieve the planned total depth due to lost circulation issues.

What Went Wrong?:

  • Well had limited offset well data, the actual pore pressure was greater than the pre-drill prediction.
  • Insufficient mud weight then led to an underbalanced well state while drilling.
  • A confirmation bias existed with the well site operations and office teams decision characterizing the first kick indication as ballooning
  • The well site team did not consult with the office team when they decided to open the well three more times.

Corrective Actions and Recommendations:

  • More stringent review of pore-pressure prediction for wells with limited off-set data must be done by office technical staff.
  • Enhanced training and drills for well site operations staff regarding ballooning guidelines and kick detection and response.
  • Improve clarity of communication between office & rig well site personnel.
  • Follow up verbal agreements with written documentation describing the exact steps agreed upon by both the well site and office staff.
  • Recognize and reinforce the understanding of what SIDPP represents and that a properly measured value (assuming the bit remains on bottom) will not change unless the mud weight or formation pressure changes.


safety alert number: 316
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.

IOGP
City Tower, 40 Basinghall Street
Level 14
London, London EC2V 5DE
United Kingdom