Near-Net-Zero Offshore Gas-to-Wire for CO2-Rich Natural Gas: Lost Power and Marginal Abatement Cost Analyses

Natural gas combined cycles with carbon capture and utilization represent reliable alternatives for decarbonized power generation with approximately net-zero emissions. This is valid even for offshore gas and oil rigs situated at remote deepwater locations where high-depth gas pipelines are costly. For such rigs, gas-to-shore is unfeasible and is often replaced by gas-to-wire analogues, wherein gas energy is exported to shore as electricity through high-voltage direct-current subsea cables. This study investigates the thermodynamic and marginal abatement cost (MAC) performances of decarbonized-gas-to-wire offshore plants firing CO2-rich natural gas, whose decarbonization was accomplished through post-combustion aqueous-monoethanolamine absorption. Thermodynamic analysis evaluated maximum work, equivalent work, lost work, and thermodynamic efficiency, with consistency guaranteed through two independent lost work calculations with only 1.14% discrepancy. The decarbonized-gas-to-wire achieved 37.7% thermodynamic efficiency with 543.4 MW lost work, while the carbon-emitting counterpart attained 53.5% efficiency and 433 MW lost work, wherein capture penalties respond for the former performance losses. The power generation and aqueous-monoethanolamine subsystems of decarbonized gas-to-wire were the major lost work sinks attaining, respectively, 72.5% and 14.4% of total lost work, being the units with greater potential for better thermodynamic performance through technology upgrading. Meanwhile, MAC analysis unveils that the decarbonized gas-to-wire environmental–economic performance can be dramatically improved through carbon utilization for enhanced oil recovery, even outperforming the carbon-emitting counterpart.