LONDON — Total, the French oil company, has disclosed the findings of its investigation into the causes of a natural gas leak at a well in the North Sea, which has shut down production on the company’s flagship Elgin-Franklin field for almost a year.
At the time of the leak, in March 2012, gas from the Elgin-Franklin complex accounted for about 7 percent of British production. The British Treasury has said the shutdown at the field lowered tax receipts and stunted economic growth.
Patrice de Viviès, the company’s senior vice president for exploration and production for Northern Europe, said Thursday that the leak was a result of corrosion caused by a reaction between grease on the threads of the well casing and bromine in the fluid used in the well, which produced stress cracks that led to a rupture.
In addition, a gas layer called Hod, which was about 1,000 meters, or 3,300 feet, above the Fulmar gas formation that was being tapped by the well, unexpectedly started producing gas, possibly because it was affected by the production from the lower layer. Mr. de Viviès called this set of circumstances unique.
“It is impossible to forecast this type of incident,” he said.
Mr. de Viviès said he did not expect penalties from the British authorities. A spokesman for the British Health and Safety Executive said the matter remained under investigation.
The comments were a reminder of how dangerous oil and gas production can be even when a company operates in a way that, by all appearances, should be safe. The well was originally installed in 2000, he said.
Total had to evacuate 238 workers from the Elgin platform — about 240 kilometers, or 150 miles, from Aberdeen, Scotland — when the leak was discovered. The platform serves a complex of fields, and there was a danger that the gas could catch fire, leading to a catastrophic incident. The well, known as G4, was plugged about two months later. The episode caused no injuries.
At the time of the shutdown, Elgin-Franklin was producing the equivalent of 140,000 barrels of oil a day in gas and liquids, making it a very large field.
Mr. de Viviès said that Total had submitted plans late last year for restarting the field and that it expected the British authorities to accept these within days. The company then plans to resume operations at the field gradually, starting with four wells, compared with 14 at the time of the leak. He said he expected production by year-end to be about 70,000 barrels a day, or half of what it was at the time of the leak.
By 2016, the company’s drilling program is expected to increase production above 140,000 barrels a day, he said.
He added that Total had learned lessons about working in fields where gas is subject to high pressure and high temperatures, and that it would operate more conservatively in the future. He also said that Total would share its findings with other companies to avoid a repeat of this type of incident.
He said the company did not blame the supplier of the well pipes, Vallourec, a company based in Boulogne-Billancourt, France.
Total is expanding its British production while other large oil companies have been selling assets to smaller companies. Its chief executive, Christophe de Margerie, has said that the company is considering becoming involved in shale gas development in Britain, “which we think has potential,” he said.
Article source: http://www.nytimes.com/2013/02/16/business/global/total-reveals-cause-of-north-sea-natural-gas-leak.html?partner=rss&emc=rss