Abstract
Re-qualification, conversion, and utilization of old existing pipeline to become CO2 pipeline based on DNV-RP-F104 become one of attractive opportunity to reduce overall CCUS CAPEX compared to laying a new CO2 pipeline. However, it comes with various technical challenges includes flow assurance, integrity status of the existing pipeline i.e. current condition of the pipeline, including limitation of existing pipeline material strength and corrosion due to overdue usage. Pipeline materials are expected to be able to resist rapid de-compression force thus preventing running ductile fracture (RDF) to happen. To also note that existing pipeline are generally corroded based on latest available in-line inspection outcome.
A comprehensive technical assessment followed by commercial assessment shall be performed in determining technical suitability of existing pipeline that to be converted into CO2 services. As a start, a study on pipeline fit-for-service (FFS) shall be performed to determine the remaining life of pipeline based on remaining wall thickness. A numerous iteration using Enhanced Battelle Two-Curve Method (e-BTCM) shall be performed for the entire length of pipeline which may comprised of various pipeline wall thickness and design specification. On top of that, process flow assurance simulation study shall be conducted in determining design and operating envelopes of the new CO2 flow regime for optimum and safe transportation of CO2 from gathering system to offshore injection reservoir. Additionally, corrosion assessment shall be performed to calculate the corrosion rate based on fluid composition and impurities thus predict remaining life of pipeline with CO2 services.
A study of 155km total length of existing pipeline is having some limitations for the conversion of the whole pipeline system to flow with CO2. One of the limitations is the first 10km of pipeline is not meeting RDF requirements. The attractive solution of the conversion whereby most of the pipeline length still can be used, while first 10km length will undergo pipeline rehabilitation such as pipeline clamping, pipeline sleeving or sectional replacement. It is observed that pipeline rehabilitation solutions play a major part in reducing total CAPEX for CO2 pipeline re-purpose. This paper will further define the challenges and resolution in delivering a low-cost solution for pipeline re-purpose in comparison to laying a ‘new’ pipeline.
Detailed assessment using e-BTCM in determining the required toughness of line pipe materials as well as optimum departing temperature has resulted in low-cost solution for CO2 pipeline re-purpose CCUS project.
