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16 Aug 2023

Unlocking Pipeline Potential: Extending Service Life for Greater Value and Sustainability

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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 growing call for the lives of older pipelines and related infrastructure to be extended. 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 understood, and to implement appropriate measures to maintain these risks within 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 understanding 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 pipeline 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 pipeline 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 expensive 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 and 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 pipeline. 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 sometimes 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. The assessment should quickly confirm and screen out any threat mechanisms which do not have an influence on whether the pipeline achieves its planned extension, while applying appropriate levels of scrutiny to those threats which do have an influence. In a small number of cases, this can require detailed engineering studies to reach the required understanding of the implications of the given threat in the pipeline’s particular context. Supporting studies include flow assurance, fatigue assessment, and consultation with experts in a specific field, such as top-of-line corrosion assessment.

The life extension study provides a new risk profile for the pipeline in its extended life. This, along with recommendations for mitigating any intolerable risks found, is the principal output of the work. The risk profile report supports informed decision-making as part of the company’s risk management strategy. For example, an expected increase in the rate of pipeline degradation may inform the need to increase future inspection frequency to confirm conditions more regularly or to identify and quantify the need for intervention or repair. Risk frameworks such as life extension output are a familiar tools to operators and provide an established basis from which to apply for and secure management approvals for any investments required to maintain acceptable future pipeline operation.

Life extension studies need to take careful account of the implications of spending in their recommendations. An ageing pipeline often requires more investment in inspection and maintenance but is less financially productive because of diminishing product flows in late life. Recommending a technically-sound but expensive inspection or intervention is not likely to be a viable option due to basic economics. The rigorous approach followed in a well-conducted life extension study will add value by providing the operator with recommendations for appropriate levels of expenditure, and only in those areas that secure target longevity for the pipeline.

A standard approach?

By looking at a pipeline through fresh eyes, all possible threats which could influence the achievement of life extension are identified and understood. The value comes from a comprehensive and bespoke approach to each study to ensure that nothing is missed.

Having said that, the framework and method by which a pipeline life extension study is performed can be standardised, and therefore repeatable. Good guidance on the extent of coverage and the processes to follow in a study is available from international bodies such as ISO and NORSOK. The real value comes from how the guidance is applied. Studies have shown that life extension is best done with a small, multidisciplinary team. An experienced team, who can quickly confirm what to look at and what to screen out, whilst understanding the key issues from the operator’s perspective, particularly when it comes to recommendations for any possible expenditure on their ageing pipelines. The tools used by the team are also important, for example how to efficiently manage the complex data gathering and interpretation to build a holistic picture of pipeline condition, relevant future threats and resulting risks, and clearly showing any changes in extended life. Experienced teams follow a systematic approach, learn from each study completed, and optimise life extension methods. This delivers a continuously improving, professional and cost-effective service in what is a complex area of pipeline engineering.

A live process

It can be tempting to think that a life extension study that confirms the feasibility of operating a pipeline for the next 20 years means that there is no need to revisit the assessment in the meantime. However, circumstances change (most commonly the pipeline’s operating conditions, and new threats or anomalies may also arise), resulting in implications for the validity of the original assessment. Life extension should be treated as a live process, with ongoing compliance subject to periodic review. In following this approach, the operator can maintain a good understanding of the changing future risks that the pipeline faces and can act when required to maintain those risks within acceptable limits.

This article was originally featured on World Pipelines, page 69, in August 2023. For the original content, click here:

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