Depleted offshore fields envisaged for re-use as CO2 storage sites are also associated to pipelines which in the past carried out hydrocarbons. The possibility of repurposing such existing infrastructures to transport anthropogenic CO2 captured onshore or even offshore represents a key factor to reduce costs, risks and environmental impacts of Carbon Capture Storage (CCS) projects. The very limited number of such offshore applications, due to the relatively new need to reuse existing O&G sealines for CO2 transport, carries the uncertainty that not all design areas are fully covered.
The paper presents the conceptual steps performed to allow a safe transport through an existing pipeline system retrofitted to CO2 transportation or a new designed pipeline: what is required for the reutilization of the existing pipeline, how the wall thickness considered for the assessment has been chosen (in presence of important metal loss features due to corrosion), how a new pipeline has been designed, the selected design and operating conditions, recommendations for further investigations. A risk assessment allowed to determine areas to be further investigated and developed to accurately determine the risk for health and environment in the worst scenarios.
Finally, the application of the principal guidelines available for CO2 sealines design is presented, particularly about the ductile fracture arrest that confirmed to be a demanding requirement. In this case, the guidelines application revealed important differences, which are discussed together with full-scale tests, model uncertainties and safety factors to be used for the Battelle Two-Curve Method (BTCM), as modified by the guidelines or according to the original formulation.