IOGP Well Control Incident Lesson Sharing
<<< Back to Results

Printable version

SHALLOW WATER FLOW IN LAND WELL


Country: ---

Location: ONSHORE : Other onshore

Incident Date: ---   Time: ---

Type of Activity: Drilling, workover, well services

Type of Injury: ---

Function: Drilling


On a remote land operation, 20" conductor was set at 27m and the diverter system nippled up. The 20" conductor was cleaned out with a 17.5" drilling assembly and drilling progressed. A carbonate formation was penetrated at 316m with 10.6 ppg mud. At 433m total losses were expereienced in the carbonate formation. An LCM pill was pumped with no impact. The drill string was pulled to 178m to mitigate hole instability and to mix more mud. Additional LCM pills were pumped with minor impact on loss rate. While at this depth, the well began flowing and the diverter was closed. While diverting, a broach occurred around the conductor pipe. Two off-bottom dynamic kill were attempted but unsuccessful at stopping water flow into the wellbore. The pipe was eventually stripped back to bottom and the well was dynamically killed with 14.5 ppg mud at 35+ BPM.

What Went Wrong?:

The shallow carbonate zone was overpressured from a water aquifer higher in elevation.

During the mud loss event, fluid hydrostatic at the top of the flow zone dropped below pore pressure and allowed the well to flow.

With the bit significantly off bottom for the first two kill attempts, building fluid hydrostatic pressure to overcome flow zone pressure was not possible. In addition, very little annulus friction pressure could be built during the dynamic kill because of the large hole size.

Corrective Actions and Recommendations:

When drilling with only a diverter installed and dynamic kill as the contingency plan for well control, always keep the bit near bottom during a mud loss event. Having the bit near bottom will maximize the amount of friction and hydrostatic pressure that can be applied to the well during a dynamic kill attempt.

If it is suspected that overpressure could exist in a shallow zone, consideration should be given to setting surface casing above the zone and installing a BOP.


safety alert number: 289
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