Repurposing the Pipeline for CO2 Transportation in the Carbon Capture and Sequestration (CCS) Project

Abstract Field D has been in production for over 40 years, and its output is now decreasing to the point of nearing abandonment conditions. This makes the field an appealing candidate for CO2 sequestration, aiding in the achievement of net zero carbon emission target while generating revenue through CO2 storage services. The processing, transportation, and sequestration of CO2 should be implemented at the minimum life cycle cost to ensure that the tariff imposed on emitters is more attractive than paying carbon tax. The tariff rate can be significantly reduced by converting the existing 205km-long natural gas pipeline from Field D facility to shore as the CO2 injection pipeline for sequestration. This work highlights several key studies conducted during the feasibility stage to evaluate the viability of repurposing existing hydrocarbon pipelines for CO2 transportation. The feasibility study covered the flow assurance aspects elaborated in this paper, focusing on selecting dense or supercritical fluid versus gas-phase transport and flow assurance issues encountered in pipelines and injection wells. Effects on pipeline design and operating philosophies were also evaluated. Worst-case operating scenarios were thoroughly examined to establish the range of acceptable moisture content, impurity composition, and corrosion concerns, taking account of the use of corrosion inhibitors. A risk assessment was also conducted to identify mitigation plans, which included, among other things, material testing to be included in the action plan. Evaluating an existing pipeline for suitability to convert to CO2 transportation service is challenging due to the need to access historical operating data and mechanical integrity data. According to the pipeline fitness for service (FFS) study, the flow assurance analysis determines the optimal design and safe operating envelope for the pipeline with CO2 service. Corrosion assessment was performed in enhanced-Multicorp software using inputs from flow assurance analysis to identify potential corrosion rates (CR) for CO2 service with presence of moisture and free water in the pipeline. The study also identified suitable corrosion inhibitors with expected dosages to suppress high corrosion rates in CO2 service when free water is present. Despite the data limitations, the feasibility of conversion was successfully demonstrated. To fully mitigate the risk, material testing on the existing pipeline will need to be conducted as a further precaution. This study offers valuable insights into the challenges and methodologies for converting existing natural gas pipeline to CO2 service in the early stage of CCS development.