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Oil Report

Statoil says unstable N.Sea well was serious risk

* Gullfaks C platform evacuated in May and shut for 2 months

* Statoil says 18 lessons to be learnt from incident

* Measures may affect costs, well productivity in some cases

OSLO, Nov 5 (Reuters) - Oil firm Statoil STL.OL will learn lessons from an incident at its North Sea Gullfaks C platform that shut output for nearly two months and was described by green activists as a possible disaster, it said on Friday.

The Norwegian company described as “serious” and involving “considerable risk potential” an incident in May that led to an evacuation of the platform after changes in well pressure led to a fault on one of two valves designed to prevent a blowout.

Production only resumed in mid-July after Statoil installed three cement plugs and one mechanical plug in the faulty well. [ID:nLDE64K06F] [ID:nLDE66D1GL]

“Any incident which implies a loss of control of the reservoir is very serious,” Oeystein Michelsen, Statoil head of production and exploration in Norway, told reporters. “It took us two months to normalise the situation. It was demanding.”

Michelsen, speaking after presenting a Statoil report on the incident to the Norwegian oil safety watchdog, said the probability of a blowout had been very low and the chance of a leakage of hydrocarbons to the environment even lower.

Gullfaks C is one of three platforms in the Tampen area of the Norwegian section of the North Sea. It handles oil and gas from the Gimle, Tordis, Vigdis, Visund, Gullfaks and Gullfaks Soer fields.

The sea depth at the site is 130 to 220 metres, with the reservoirs 1,700 to 2,000 metres below the sea level.

“SCARY”

A leading Norwegian environmentalist group said the report showed the incident at Gullfaks C held similarities with the BP BP.L Macondo oil spill in the Gulf of Mexico. "It is scary reading," said Fredric Hauge, head of the green group Bellona.

“They lost two barriers (in the well) and had gas on the platform. It is completely unacceptable,” he told Reuters.

Michelsen said Statoil had identified 18 lessons from the event that would improve their operations, including “improving and upgrading equipment and methods,” or practical measures to ensure “competence, continuity and quality” in the way work is implemented.

“In some cases, this may affect costs and the productivity of a well,” Michelsen told Reuters in a phone interview.

The Petroleum Safety Authority Norway (PSA), which received the report on Friday and has made its own assessment of the situation since May, said the incident at Gullfaks C was “very serious.”

“They had a ‘well kick’ and a well without all the barriers intact,” PSA spokeswoman Inger Anda told Reuters. “It could have caused a blowout.”

She said the PSA would compare the reports and report back within a couple of weeks.

A ‘well kick’ happens when the pressure of oil and gas is greater than that of the fluids used during drilling and enters the wellbore. (Editing by James Jukwey)

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