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Well integrity: No grounds for well complacency

Wells cannot be treated lightly. Every one of them needs to be cared for properly, or they can cause trouble.

This article was published in the publication "Safety - status and signals 2010-2011".

Over 4 500 exploration and production wells have been drilled on the NCS to date. Names and goals may differ,  but all share one feature – they are far more than a simple hole in the ground.

Like fixed installations and other petroleum industry facilities, wells need to be maintained and monitored to prevent faults and incidents.

The most critical components are valves, seals, tubular joints and similar equipment. External barriers – entrenchment in the geological formations – are also very important for safety. And corrosion and erosion present major challenges over time.

Although Norway has a good history for serious accidents caused by well leaks and failures, PSA principal engineer Arne Mikael Enoksen urges caution in resting on one’s laurels.

“At the same time as their number is rising, wells on the NCS are getting older,” he points out. “The industry has an important job to do here.

“Developing and adopting methods and equipment which can effectively monitor well condition and spot leaks and failures as early as possible is a demanding business.”

He reports that an extensive PSA study of data from more than 400 selected wells in 2004 found that 18 per cent – a high proportion – faced challenges from leaks and barrier failure.

“About the same time as this work was launched, we experienced the very serious blowout on Snorre A in the North Sea, when large volumes of gas flowed from the seabed just under the platform.

“This incident demonstrated with full clarity the possible consequences of a well leak, and gave an extra boost to work on this issue.”

Confronted with the facts from the PSA’s review, the industry undertook in 2007 to extend the project by establishing an overview of and categorising well status.

More than 1 700 wells have so far been subject to this evaluation, and the results obtained are also included in the PSA’s annual RNNP report.

Mr Enoksen is pleased that the industry has established a special Well Integrity Forum (WIF), involving eight key production operators with the PSA as an observer.

“This body holds regular meetings,” he notes. “An important job is the development of “stoplight” criteria – categorising possible well problems by character and seriousness, so that corrective measures can be applied in the right place and at the right time.”

At the WIF’s suggestion, the OLF has now prepared well integrity guidelines. These cover a wide range of important factors, such as education, experience transfer, barrier philosophy and stoplight criteria.

“These guidelines should mean that the industry is now much better equipped to meet the challenge of ensuring that wells are intact at all times,” Mr Enoksen observes.

This article was published in the publication "Safety - status and signals 2010-2011".