On March 25, 2012, a gas leak accompanied by small volumes of condensate — a light liquid hydrocarbon — occurred on the G4 wellhead on the Elgin platform. The Elgin field is located 240 kilometers east of Aberdeen in the British North Sea. The priority was to ensure the safety of the 238 people working on the Elgin complex, then to secure the platform.
From the outset, Total cooperated closely with the U.K. authorities.
1. How did you stop the gas leak?
The leak was stopped on May 15 after mud was injected into the well. The well was then plugged with five cement plugs, the last of which was set in place on October 22, 2012, creating a 1,000-meter thick barrier.
2. Do you know what caused the gas leak?
The leak was caused by a combination of events, some of which would have been difficult to foresee. In one, a casing from the G4 well fractured at a pressure that was 30% below the design pressure, due to an occurrence of corrosion that had never before been encountered in the industry and was specific to the G4 well. In the other, a change in the geomechanical characteristics of the chalk Hod formation — originally non-producing — located approximately 1,000 meters above the producing reservoir caused gas to travel from it.
3. Why didn’t production resume until nine months after the gas leak was halted?
After the incident, our teams worked on two fronts:
- Securing the G4 well after the leak was halted on May 15, an operation finalized in October 2012 when five cement plugs, each 200 meters thick, were put in place, securing certain similar wells on both Elgin and Franklin.
- Learning all possible lessons from the accident and preparing to restart production. The latter included cleaning the platform and the facilities.
The integrity criteria for the Elgin/Franklin wells and operating procedures were reviewed in light of the lessons learned. A revised safety case was submitted in late November 2012 to the Health and Safety Executive. The U.K. regulator recently approved it.
4. Why are operations resuming only partially?
Total’s teams carefully planned and prepared the restart so that it takes place in complete safety.
Based on the revised well integrity criteria and the new operating procedures introduced after the G4 incident, production is resuming progressively from four wells, two on Elgin and two on Franklin.
The four wells concerned represent a production capacity of around 70,000 barrels of oil equivalent per day, or half of Elgin/Franklin’s production before the G4 well incident. We are also evaluating the option of resuming production from five more wells, which would require workovers.
To get back to the full pre-incident production level by 2015, a redevelopment plan that will include drilling new infill wells on Elgin/Franklin is being studied. In addition, West Franklin Phase II development is ongoing, with production set to start in 2014. Any wells not restarted will be permanently abandoned.
5. What measures have you taken to ensure that this type of accident does not recur?
Well integrity criteria have been revised and new operating procedures have been introduced to reflect the lessons learned from the G4 well incident.
6. How did the gas leak impact the environment?
Analyses performed by Total and the U.K. authorities indicate that the overall impact on the environment was negligible. The gas that leaked dissipated naturally. Most of the condensate evaporated, while the remaining sheen concentrated on the surface also dispersed or evaporated in a few days.
7. Are there any similarities with the Macondo incident?
This incident is not comparable to the Macondo incident. Everyone was evacuated safely, the environmental impact was negligible and no facilities were damaged. The leak occurred on a platform above water and consisted mainly of gas and a small amount of condensate.