There is currently a strong interest to explore the use of existing pipeline subsea infrastructures to transport carbon dioxide (CO2), either in dense (liquid) or gas phase as a part of the new energy mix. Pipelines will play a critical role in transporting this energy mix, but carry safety and financial risks if new design, construction, and operational considerations are not considered. Change of product will per applicable pipeline design codes require a re-qualification to ensure that the new premises for change in operation is properly assessed and confirmed acceptable with respect to pipeline safety, reliability, operability and transport capacity. Per DNV-ST-F101, Sec.11.E, re-qualification involves re-assessment of the pipeline system for the new premises. A work process for re-qualification of pipelines to operation with CO2 is provided in DNV-RP-F104 ‘Design and Operation of CO2 pipelines. Several decades of industry experience exists for onshore CO2 pipelines but the experience is rather limited for offshore pipelines. Research is underway to determine how new and existing pipeline materials will react to the different compositions, pressures and temperatures these pipelines will operate under. Impurities in captured CO2 affect critical pressure, critical temperature, and phase behavior and have an impact on pipeline design parameters. Key considerations and requirements relevant for both new and repurposed pipelines transporting CO2 with main focus on the structural integrity will be discussed based on recent project experience.
Safely repurposing existing pipeline-infrastructure for CO2 transport – Key issues to be addressed
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