Jee Ltd, a leading subsea engineering consultancy, has successfully completed a life extension (LTE) assessment for two critical subsea flowlines in the North Sea, reinforcing its position as a trusted partner in offshore integrity management.
Overview
The Dua field is tied back to an FPSO by two 10” looped flowlines. One pipeline provided round trip pigging and gas lift capability from the FPSO while the second transported production fluids back to the facility. Both pipelines were commissioned in 2014 with an original design life of ten years.
With the design life due to expire in 2024 the operator required a lifetime extension assessment to meet regulatory requirements and to confirm whether additional assurance activities were needed to support continued extended life operation.
Solution
The lifetime extension assessment followed the methodology defined in ISO TS 12747 and NORSOK Y 002 supplemented by guidance from DNV RP F116 with due consideration of applicable local standards. The assessment was structured around five defined stages:
- Determination of the LTE requirements
- Assessment of the integrity of the pipeline system and review of the operational history.
- Identification of the threats and time-dependant degradation mechanisms to the pipeline system in extended life.
- Assessment of any identified threats to the pipeline during the extended operating period, determining the need for any mitigation and remediation measures.
- Implementation of the LTE and specification of inspection and monitoring requirements to ensure fitness-for-service of the pipeline during future operation.
Jee developed a Basis of Analysis document for the LTE assessment of the pipeline system including pipework within key manifolds. Additionally, an umbilical running from the FPSO to the Twin Pipeline Active Manifold was also included in the pipelines LTE assessment. Key data relating to the pipelines and associated pipework was compiled in this document. The properties and operating data of the pipelines system were detailed within the BoA which was reviewed and agreed with the client, the information contained within the BoA comprised the input data for the LTE assessment.
A current integrity assessment was then completed to establish a baseline view of pipeline condition. In line with ISO TS 12747 this included review of available PIMS data inspection history and operational records. The integrity review confirmed that the condition of both pipelines was acceptable and that the lifetime extension assessment could be progressed.
Following this confirmation Jee completed a structured risk assessment to identify threats and time dependent degradation mechanisms relevant to extended life operation. To support efficient implementation this assessment combined lifetime extension and inspection and monitoring requirements. The risk assessment was prepopulated by Jee and reviewed during a workshop attended by the client and their independent verification body.
Based on the agreed risk profile Jee completed a risk-based inspection process. This assessed risks to the pipelines and associated subsea structures across applicable threats and defined appropriate inspection intervals monitoring activities sampling and testing requirements to manage integrity throughout extended life.
Key Findings and Outcome
The lifetime extension assessment concluded that the pipeline system was fit for continued operation beyond its original design life. A series of practical recommendations were provided to support ongoing integrity management during extended life.
The combined lifetime extension and risk-based inspection approach provided an efficient and robust framework allowing the operator to progress extended operation with an updated inspection and monitoring regime aligned to actual integrity risks.
For more information, visit www.jee.co.uk/integrity-management
To contact our Head of Integrity Management, Graham Wilson, email graham.wilson@jee.co.uk, or call +44 (0)1732 371 371.
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