Session: 04-04-05 Free Spans and Routing

Paper Number: 127939

127939 - Free Span Assessment - Benchmarking and Field Application 

Subsea pipelines can experience fatigue failure due to vortex-induced vibrations (VIV) where free spans occur. Therefore, fatigue damage must be carefully considered during the design process, and the pipeline should be regularly monitored after installation. The assessment of pipeline spans involves many non-linearities, including those arising from the pipeline's mechanical behaviour, soil properties, and hydrodynamic loading; as well as the interaction between these factors. Failure to capture these non-linearities may lead to inadequate design outcomes, which can escalate the cost of remedial works or lead to remediation when not necessary.

This paper provides an overview of assessing free spans in subsea pipelines, emphasizing the need for less conservative methodology with realistic assumptions. It highlights modal analysis and full fatigue analysis as valuable tools for understanding span behaviour. Modal analysis reveals pipeline dynamics, while full fatigue analysis estimates fatigue life, ensuring an accurate span assessment. For quality control and enhancing the reliability of assessment methodologies, the model has been benchmarked against published data in terms of modal analysis and against industrial fatigue assessment packages in terms of fatigue analysis. The proposed model showed excellent agreement with both benchmarking stages. After verification, the proposed model was used to assess the fatigue life of a critical free span.  The paper also outlines future work, including field data analysis, sensitivity studies, and statistical approaches to improve free span assessment in subsea pipelines.

Presenting Author: Mohammed Abdelsalam The University of Western Australia

Presenting Author Biography: Mohammed is a PhD Candidate at the University of Western Australia working on the assessment of free spanning pipelines. He worked as a Subsea Pipeline Engineer and has over 6 years of experience in the oil and gas industry at national and multinational companies.

Mohammed obtained his Bachelor of Science (BSc) and Master of Science (MSc) degrees from Alexandria University in Naval Architecture and Marine Engineering in 2013 and 2022 respectively. He also received a diploma in Metal Machining from Technological College, Egypt in 2008.

Mohammed has research expertise in subsea pipelines, fluid-soil-pipe interaction, finite element analysis, dynamics and vibration, mesh generation, and computational geometry.

Authors:

Mohammed Abdelsalam The University of Western Australia
Ali Karrech The University of Western Australia
Fraser Bransby The University of Western Australia
Phil Watson The University of Western Australia
Hongwei An The University of Western Australia