Mitigation of Pipeline Walking
Client: Confidential
Region: North Sea
Project: Mitigation of Pipeline Walking
Sector: Subsea Pipelines
The North Sea field production flowlines operate at high temperature and are susceptible to lateral buckling and walking. Members of the Crondall Energy team had previous experience providing operational support and identify any potential integrity issues. In the past the field had experienced pipeline slugging issues which were resolved by the work performed by Crondall Energy engineers. The operational support by our engineers continues which resulted in the identification of pipeline walking issues.
The Challenge
Routine ROV surveys had shown continued ratcheting movement of the sliding flowline termination assembly (FTA). Expansion of the pipeline end is to be expected, however, when the movement ratches it suggests that pipeline walking may be occurring. The survey video also confirmed that the FTA structure had slid up to the stops which was a significant concern. The client approached Crondall Energy to confirm if the pipeline was walking through finite element analysis and determine a mitigation plan to prevent future walking.
What We Did
Performed a muti-year survey review to investigate the changes to the pipeline over time. This included issues such as:
Lateral buckling
Pipeline Walking
Pipeline Spanning
Seabed Scour
Performed an operating data (pressure & temperature) review to determine the number of operating cycles and associated walking rate.
Developed a FEA model of the pipeline including the FTA structure including sliding mechanism.
Through analysis, matched the observed buckling behavior of the pipeline and walking rate.
Performed integrity checks of the pipeline in its most recent condition.
Determine the optimal location and required restraint of the mitigation to prevent further pipeline walking.
Developed a bespoke pipe clamping mattress (PCM) solution and model its effectiveness through FEA.
Provided technical assistance during centrifuge testing of the PCM solution.
Key Results
✅ Pipeline Walking Confirmed and Quantified: Finite Element Analysis (FEA) successfully replicated observed pipeline behaviour, confirming active pipeline walking and validating the underlying driving mechanisms.
✅ Effective Mitigation Strategy Developed: An optimally located, bespoke pipe clamping mattress (PCM) solution was designed and proven through detailed FEA and centrifuge testing to prevent further pipeline walking.
✅ Asset Integrity Secured: Integrity checks confirmed the pipeline remained fit for service, enabling continued safe operation and avoiding unplanned intervention or production disruption.
Impact
Provided an engineered, cost-effective solution to a challenging problem.
Decades of experience in subsea pipeline lateral buckling, walking and spanning assessments.
Allowed the operator to continue operating the field with confidence in its integrity.