An Introduction to Well Integrity Handbook

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FREE DOWNLOAD AN INTRODUCTION TO WELL INTEGRITY

There has been a significant technological evolution in the drilling industry during the past 30years. The early platforms on the Norwegian Continental Shelf were designed for wells with a reach of 3 km from the platform. To cover a large reservoir often several platforms were required. Examples are Statfjord A, B and C, and Gullfaks A, B and C. As these platforms were very expensive, alternative solutions were pursued such as subsea installations and extended reach wells. Today it is possible to reach targets 12 km from the platform. One new platform can replace three old platforms from a reservoir coverage point of view.

The technical evolution exemplified above requires technology and improvement on very many levels. Obviously since the wells are much longer, the risk of failure is also increased. Unfortunately, the high number of elements that can possibly fail makes the analysis difficult.

Well Integrity can in its simplest definition be defined as a condition of a well in operation that has full functionality and two qualified well barrier envelopes. Any deviation from this state is a minor or major well integrity issue. Common integrity issues are often related to leaks in tubular or valves, but can also be related the reservoir issues as loss of zonal control. Any factor that leads to a functional failure is a loss of well integrity. The challenge is of course to define all possible scenarios.

Also Read : The Definition of Well Integrity

History shows some severe examples of losing integrity in wells such as the Phillips Petroleum’s Bravo blowout in 1977, Saga Petroleum’s underground blowout in 1989, Statoil’s blowout on Snorre in 2004, and BP’s Macondo blowout in the Gulf of Mexico in 2010. These serious accidents remind us of the potential dangers in the oil and gas industry and they are some of the main drivers for the current focus on well integrity in the industry.

The Petroleum Safety Authority (PSA) initiated a pilot study in 2006, which has resulted in a continuous activity in well integrity. The pilot study was based on supervisory audits and input from seven operating companies, including 12 offshore facilities and 406 wells and presents a snapshot of the well integrity status of the selected wells at the time. The results indicated that 18 % of the wells in the survey had integrity failures, issues or uncertainties and 7 % of these were shut in because of well integrity issues. A later study indicated that each fifth production well and each third injection well may suffer from well integrity issues. An interesting observation was that old wells had few well integrity issues, actually most 9 problems occurred in the age group 5-14 years. These conclusions are not general but are limited to the studies referred to.

It is clear from the above description that well integrity is an important safety aspect of a well. However, some of the issues are not critical, whereas some may lead to accidents.

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