Printable version

Country: CANADA - North America

Location: ---

Incident Date: ---   Time: ---

Type of Activity: ---

Cause: ---

Function: ---

While drilling an Exploratory gas well in Northern Alberta with 1400kg/m³ fluid density the mud motor stalled. A highly over pressured fracture was penetrated and a gas influx entered the wellbore. The well was shut in and conventional well control procedures were implemented. Maximum Allowable Casing Pressure (MACP) was exceeded and the Low Choke Method of well control was utilized. Within one hour of the kick the high gas rate through the degasser had emptied the mud tank and circulation with the mud pump was no longer possible. At this time the well had been opened direct to flare in an effort not to exceed MACP and maximum allowable surface equipment pressures. Vented gas became present around well center indicating a potential casing seat failure and / or surface BOP equipment failure. All engines and electrical generation equipment were shut down. All non essential personnel were evacuated from location due to an increasing presence of non-ignited gas around well center and high manifold pressures.

Essential personnel remained on location; however were also evacuated due to increasing pressures and non-ignited gas at surface.

Approximately 4.5 hours after the kick was initially taken, the flowing gas ignited at well center causing the destruction of most surface equipment on site. There were no injuries to personnel during the course of the incident. There was no appreciable damage to the environment. There were no residents or other surface developments located within the Emergency Planning Zone.

Unexpected Formation Capabilities

• The progression from kick to blowout occurred, as a result of an unexpectedly high gas rate and surface pressures.

Contributing Factors:

• Cleaning, inspection and Engineering analysis, by a third party Engineering firm, revealed a leak path in the casing bowl blind flange ring gasket, which was the cause of the vented gas at well center.
• Extensive erosion was noted, on the ID of the casing bowl and the internal face of the blind flange.

Implement the following protocol and procedures on all wells with potential to penetrate high rate (AOFP > 1000e3m³/d), high pressure (pressure gradient > 16.0kPa/m) gas reservoirs and / or wells with no analogous reservoir information (as per ERCB Directive 056; New Pool Wildcat, Lahee classification) within a search radius of 30km (six times the radius recommended by ERCB Directive 008)

Install a minimum Class V BOP system.

Set intermediate casing if the FIT (Formation Integrity Test) at midpoint to targeted well depth is less than 18.0kPa/m equivalent gradient.

Utilize well test equipment while drilling to flow a minimum of 1980e3m³/d gas.

Safety Alert number: 238
IOGP Safety Alerts 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.