Chapter 17. Life Extension and Integrity Management of Ageing Pipelines Available to Purchase

There are large number of export pipelines installed and operating worldwide, conveying fluids from offshore fields to available land-based processing facilities. Many of these pipelines have now exceeded that original design life and are now in an ageing phase.

There are two main time dependent degradation mechanisms for pipeline, namely corrosion and fatigue. Consideration of these is critical in establishing the safe operating life of a pipeline, whether it is the original life or the extended life. In addition, there are other degradation mechanisms, such as erosion and accidental damage, for example from trawl boards or extreme storms. Operational pressure fluctuations and changes such as the hydrocarbon composition can also be a major source of long-term degradation. An example would be the presence of H2S, due to reservoir souring with time. This may give rise to sulphide stress corrosion cracking for pipelines that are not originally designed for sour service.

Pipeline integrity management is a key process to ensure continuing safety and loss prevention, which is particularly important for ageing pipelines. Assessment of pipeline integrity can be conducted using several industry standards and guidelines.

In many countries, pipelines that can cause a major accident or loss require regulatory approval. For example, in the UK this includes the preparation of a ‘major accident prevention document’, which assesses hazards, evaluates risk, together with a safety management system.

Inspection of pipelines has developed over many years enabling damage to be detected effectively, both internally and externally. Monitoring of fluids is also undertaken on a regular basis, to provide data on the condition of the line. Repair of damage pipelines has been undertaken using both welding and clamp technology. Robotic repair of damaged pipelines is also developing.

This paper will investigate the required assessment process for the life extension of ageing pipelines and the integrity management of these in the life extension phase, which requires a similar treatment to the assessment and management of aging structures.