Optimizing CO2 Transport and Injection for a Large-Scale CCS Demonstration Project in Korea: Flow Assurance in Repurposed Offshore Pipelines and Depleted Gas Reservoirs

Abstract This study explores the feasibility of CO2 transportation and injection for Korea's 1st large-scale carbon capture and storage (CCS) project in a depleted gas reservoir in the East Sea, South Korea. In this study, the necessity of heating CO2 at the offshore platform is examined. Operating envelope of the CO2 injector in light of near-wellbore Joule-Thompson (JT) cooling and hydrate formation is also investigated. The study informs the basis of facility design to attain the CO2 injection target. Transient thermo-hydraulic simulations using OLGA were conducted to establish the safe operating envelope and optimal injection strategy. The study considered re-using the existing flowlines, offshore platforms, and wells. Two development strategies were considered, with or without heating CO2 at the offshore platform. Two reservoir pressures were considered: early life and late life. Hydrate formation risk in flowlines, well and near-wellbore areas were assessed. This study assesses various methods to mitigate hydrate formation in CO2 injection wells within CCS projects. Each tested concept has distinct advantages and drawbacks, emphasizing the need for optimizing transport and injection systems to minimize energy consumption during steady injection. The primary discovery indicates that implementing an early injection strategy is crucial for preventing hydrate formation in CO2 injection wells. The study reveals that heating CO2 during the initial injection phase proves ineffective in averting near-wellbore hydrate formation, mainly due to substantial heat dissipation in the subsea flowline. Furthermore, even with heating, fluid temperatures near the sandface drop below freezing, creating favorable conditions for hydrate formation. This approach enhances the economic viability of CCS projects by eliminating the need for costly mitigation methods, rendering them more financially appealing. This study addresses CO2 injection challenges in highly depleted reservoirs for geologic sequestration. Our systematic approach optimizes transport and injection systems, thereby improving CCS project economics and making depleted fields more attractive for CO2 storage. Our results provide valuable insights into the feasibility of large-scale CCS in depleted oil and gas reservoirs, offering cost-effective hydrate mitigation methods, supporting viable CCS solutions, and contributing to global greenhouse gas reduction efforts.