Prism Energy Oversee 240km Cleaning and ILI Pigging Scope

Spanning across two years from the initial planning stages through to execution the scope was ultimately successful, securing the future of the pipeline and supply of gas to the UK. 


The project involved the cleaning and in-line-inspection pigging of a major 34” export pipeline which supplies 20% of the UK’s gas. Prism energy’s role was to actively manage the scope for the operator from project kick off through to acceptance of the final in-line-inspection report. This included supplying the technical pipeline engineering resources, planning the scope & managing the budget, coordinating all interfaces, facilitating all workshops and supporting at site during pigging execution.  


This complex scope, which took two years to plan and execute, involved long distance (240km) round trip pigging of a pipeline system which had not been pigged since commissioning 16 years ago. The unique pipeline profile was such that pigs had to navigate an extreme sea depth range, including thick walled pipeline sections at the deeper parts of the system.

The biggest challenge on this project was the uncertainty over the potential volume of sand and debris in the pipeline system. This uncertainty remained until the first pig run was completed, and the progressive cleaning pigging programme was designed to accommodate both the low end (<10Te) and high end (>200Te) estimates of solids in the pipeline system.

Requiring full shut down of production to facilitate the required multiple pig runs, minimising deferment was a key value driver and the top risk of a stuck pig was actively and successfully managed throughout the project lifecycle.

Long-Term Benefits

Successfully executing the progressive cleaning pigging programme has not only facilitated the in-line-inspection pigging, but also removed the risk of any future under deposit corrosion. Gaining good quality inspection data has allowed the operator to demonstrate integrity of their asset through to the end of design life.