Repurposing Submarine Hydrocarbon Pipelines for Dense Phase CO2 Transport

Abstract 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.