Shaun Walker, Victor Ng and Jeremy Summers, Kent, UK, discuss extending service life for greater value and sustainability.
As pipelines age, degradation mechanisms lead to an increase in the likelihood of failure, with implications including safety, environmental, energy security and commercial impacts. However, in recent years there is a grow-ing call for the lives of older pipelines and related infrastructure to be ex-tended. This is sometimes to maximise hydrocarbon recovery from an existing field or increasingly, as the energy market transitions, to repurpose the pipeline for alternative use, such as carrying CO2 or hydrogen.
Pipeline operators have legal duties, and societal and commercial imperatives, to ensure that a pipeline’s current and evolving future risks are under-stood, and to implement appropriate measures to maintain these risks with-in tolerable levels. As a pipeline reaches the end of its original design life, formal life extension assessments can confirm the feasibility of further service. These assessments demonstrate that the risks in extended life can be managed within acceptable levels.
Establishing a basis
The first step of a life extension study is to develop a detailed understand-ing of the current condition of the pipeline. This process can be data intensive as it brings a requirement to understand how the design and operation of the pipeline to date combine to give its current risk profile. Data reviewed includes wide-ranging design, fabrication and operational information, as well as integrity reviews and any defect assessments. The results establish a reliable baseline from which the feasibility of continued pipeline operation in extended life can be determined.
Data gathering is challenging and time-consuming. The information is often spread across many operator teams and systems, and sometimes the pipe-line is with its second or third owner. But the effort pays off as the data review process brings some significant benefits. It is unlikely that the pipe-line will have recently had such a rigorous review of its integrity and operating history, giving the operator a new perspective on the current pipeline risks. This can lead to improvements in the day-to-day integrity management of the pipeline and, in some cases, help to justify the deferral of ex-pensive planned work such as inline, intelligent pigging inspection.
Understanding the threats
Once the current condition of the pipeline is understood, the next step is to confirm and assess which threats may impact life extension. The knowledge gained from the data review process is nothing without the right level and mix of experience and knowledge across a range of technical disciplines to interpret the data. Only then can the right questions be framed that are relevant to life extension. Pipeline integrity specialists manage this process, supported by materials and corrosion, flow assurance and analysis engineers, and occasionally other specialists such as valves, controls and instrumentation engineers.
Operator anomaly databases are routinely reviewed as part of life extension assessments because these are summaries of known issues with the pipe-line. These databases typically have numerous recorded anomalies, the majority of which can normally be readily screened out as they do not have a significant bearing on life extension. Conversely, a review of data some-times identifies threats which had not been identified by the operator, and if left unchecked, may present a current or future significant integrity concern.
Focus on the relevant factors
Some pipeline life extension studies we have seen have comprised little more than a repeat of the original design calculations with updated numbers. Whilst it is necessary to confirm that the pipeline can withstand future mechanical loading, this is only part of the story. Most of the focus usually needs to be on degradation-related threats which could compromise the pipeline integrity over time, such as internal and external corrosion or fatigue.
The elements of success
Pipeline operators routinely assess the integrity of their pipeline systems as part of ongoing asset management, and typically perform annual integrity reviews for their whole pipeline portfolio. These updates, which often involve revisiting thousands of individual risk assessments, are invariably done in addition to the normal operational workload. With the additional pressure of reporting to senior management or the regulator by a specific deadline, this leaves little time to delve into details. In these circumstances, it can be easy to overlook new or evolving degradation trends affecting pipelines, which may manifest over a long period of time.
Identifying the relevant areas to study and assessing them to the right level of detail is what makes life extension studies successful…
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Read the article online at: https://www.worldpipelines.com/special-reports/17082023/unlocking-pipeline-potential/
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