Challenge

With the production field approaching the end of its design life in 2021, the client contracted Penspen to perform a life extension study focused on demonstrating the fitness for service of the pipelines through to 2031 – a further 10 years. 

Services

The scope of this life extension study was to perform an integrity assessment of the corrosion features reported by the latest intelligent in-line inspections, and: 

• Determine the remaining life
• Identify safe working pressure variations overtime  
• Determine the critical corrosion features limiting the remaining life  
• Perform more advanced assessments where appropriate

Solution

In order to undertake the required study, Penspen has carried out a structured life extension study in line with ISO/TS 12747 recommendations. The following were also considered in the study: 

• Integrity assessment following the methodology specified in DNV-RP-F101 2019 Corroded Pipelines, supplemented by BS 7910 Annex G 
• Assessment was performed for every year between 2021 and 2040 in order to determine the variation in the safe working pressure of the pipeline over this time period 
• Corrosion growth distributions, as specified by the client, were used to grow the reported corrosion feature dimensions with time
• Multiple sensitivities studies were performed for a range of corrosion growth rates in order to determine how future corrosion growth rate would impact the remnant life of the production field 
• Cost benefit analysis to support long-term decision-making 

 For each segment, and the pipeline where applicable, clear visual representations of the results of the integrity assessment were produced in the form of: 

• Failure assessment diagrams showing the reported features assessed against applicable integrity limits
• The safe working pressure of the segment/pipeline with time
• The number of features becoming critical as time progresses 

Result

The Life Extension Study successfully determined the remnant life and safe working pressure variation with time for the production field and pipelines, with identification of critical features that were controlling the remnant life included.

In addition, the client benefited from clear visualisations produced in the form of charts and drawings, to be easily communicated with relevant parties.

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