Repurposing Submarine Hydrocarbon Pipelines for Dense Phase CO₂ Transport

Carbon Capture and Storage (CCS) will play a crucial role in the energy transition. Natural gas developments must continue for decades to meet growing energy demands and to concurrently enable the transition from fossil fuels to renewable energy generation. Stripping the CO₂ from the natural gas and disposing it into depleted reservoirs will be essential to reduce harmful emissions during the transition. Many depleted offshore natural gas fields are planned for CCS. They will require a submarine pipeline that transports CO₂ from an onshore processing facility to the field.

CO₂ has been transported via onshore pipelines for several decades, however there is less global experience in the design, construction, and operation of submarine CO₂ pipelines. In many cases the CO₂ needs to be transported in dense phase for efficiency. The complex properties of dense phase CO₂, combined with the technical and operational challenges of a carbon steel pipeline in a wet environment, create an engineering challenge that has only recently been uncovered. A potential attractive option is to repurpose existing hydrocarbon pipelines to transport dense phase CO₂. This has significant benefits. There is no need to perform seabed route surveys, purchase linepipe materials, and construct a new pipeline. However, repurposing existing pipelines for dense phase CO₂ transport is not always a feasible or safe option.

This paper utilizes the foundations outlined within the DNV industry standards to propose a high-level screening methodology that aims to quickly understand if existing hydrocarbon pipelines have the potential to be re-qualified for dense phase CO₂ transport. Two case studies are presented to illustrate how this methodology can be applied, with different outcomes.