Quality and sound judgement lead to a long life

What is the lifetime of a platform, pipeline or subsea facility? In short: Often much longer than planned.

The facilities on the Norwegian continental shelf are growing older, and modern technology, new operating methods and targeted measures are enabling more oil and gas to be recovered than originally planned for. The licensees therefore often opt to use the facilities even after they have reached their design lifetime. 

Extending the lifetime can often make sound socio-economic sense. That said, safety must never be compromised for the sake of life extension. 

It is a fundamental requirement that safety levels should be equal in all phases of petroleum activities. Put simply: It must be equally safe to work on an old platform as on a new one. 

Norway has, over time, developed a robust infrastructure for petroleum activities, making it possible to extend the lifetime of many facilities. The success criteria have been solid project management during the development and modifications phases, systematic maintenance and a consistent emphasis on quality. A high activity level and a long-term perspective for the NCS also necessitate continuous work on the framework conditions pertaining to operators and suppliers. 

Safe lifetime extension requires the companies to apply this knowledge in design, construction and operation.

Three things 

Lifetime extension depends on more than technical calculations and financial assessments. It is about ensuring that the facility can function safely and efficiently, even after its´ original lifetime has expired. 

“In short; three requirements must be fulfilled to extend a facility´s lifetime," explains Gerhard Ersdal, who has been key to Havtil's work on lifetime extension for many years.  

"Firstly, you have to design and build robust facilities. 
Secondly, the facilities must be inspectable. 
Thirdly, the facilities must be repairable.  
 
The requirements apply to all petroleum facilities, above or below water. For pipelines, it is particularly important to have inspection and repair methods in place," he says. 

Ersdal works in Havtil's technical area for structural safety, holds a PhD in lifetime extension of ageing offshore structures and is the co-author of several textbooks on the topic.

Through supervisory work and professional development, he has helped to build our expertise in the area. 
He emphasizes that lifetime extension is an interdisciplinary topic encompassing materials technology and marine structures, operation, maintenance and risk management. 

"The industry has in-depth expertise in lifetime extension and what is required. It is important that this knowledge is applied actively, and that decisions are made from a holistic and long-term perspective,” Ersdal points out. 

"Safe lifetime extension requires the companies to apply this knowledge in design, construction and operation.” 

Concept definitions 

Extended lifetime 
When the licensees submit a plan for development and operation (PDO) for a field, a report detailing the expected lifetime of the facilities must be included. If the licensees wish to operate the facilities for longer than planned, approval must be applied for stretching beyond the originally planned lifetime. 
 
Design Lifetime 
Design lifetime is the length of time the facility is designed to last for in terms of fatigue, corrosion and such. 
 
Life expectancy 
Life expectancy is the time the facility is expected to be in production. This may be either shorter or longer than the design lifetime.  

Example: The concrete jacket on Troll A has a design lifetime of 70 years. Structures in the superstructure have a shorter design lifetime, however, because they are easier to replace during the facility's expected lifetime.  
 
PDO 
The plan for development and operation (PDO) is approved by the Ministry of Energy or by the Storting, depending on the size (development cost) of the project. The PDO must detail the design lifetime of load-bearing structures.  

Havtil is responsible for assessing PDO applications for conformance with the requirements of the HSE regulations, and for making a subsequently informed recommendation to the Ministry. 

Operation beyond the originally planned lifetime requires a separate PDO. The same rules apply to petroleum facilities onshore.