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Safety Bulletin 2003-02
September 30, 2003
DOWNHOLE EXPLOSION/SWEET GAS BLOWOUT
During a recent snubbing completion of a well, a downhole explosion occurred, causing a complete failure of the well’s production casing, surface casing, and production tubing.
The production tubing was propelled through the casing rupture and exited at ground level about 1 metre (m) from the wellhead. The tubing string reached an estimated height of 1200 m and landed about 50 m from the wellhead. This resulted in an uncontrolled flow of sweet natural gas at an estimated rate of 3000 to 5000 cubic metres per day, as well as a mist of oil.
Post-incident investigations by the operator and the Alberta Energy and Utilities Board (EUB) identified that
- air had been introduced into the wellbore for use as a cleanout fluid, and
- there was incomplete purging of air from the snubbing equipment.
Recommendations
In order to prevent the recurrence of a similar incident, the EUB recommends that companies engaged in snubbing operations should consider the following:
- Air should not be used as a cleanout fluid on wells where hydrocarbon liquids are known or thought to be present in any amount.
- Snubbing units should purge all air from the BOP and snubbing equipment prior to snubbing tubing into any well.
Contact
For more information about on-site inspections of energy facilities, communicating with residents and landowners, and oil and gas incidents and emergencies, contact the EUB Field Centre near you:
To call toll free, first dial 310-0000
Bonnyville (780) 826-5352
Drayton Valley (780) 542-5182
Grande Prairie (780) 538-5138
Medicine Hat (403) 527-3385
Midnapore (403) 297-8303
Red Deer (403) 340-5454
St. Albert (780) 460-3800
Wainwright (780) 842-7570
