Low-emission Gas-to-Wire with thermodynamic efficiency: Monetization of carbon dioxide rich natural gas from offshore fields

Natural gas is important during fossil-to-renewable energy transition and its production in remote offshore oil-&-gas fields – even at high %CO2 – is increasing. The prime Research-Question addressed here is: Given the existence of expressive CO2-rich NG reserves at remotely located offshore oil-&-gas field at deep-waters, are there recognizable differences on technical, economic, thermodynamic and sustainability grounds between Offshore Gas-to-Wire-CCS (on floating rig) or onshore (with pipeline tiebacks to field)? Post-combustion capture is assumed in both solutions generating enhanced oil recovery revenues from CO2 utilization. Gas-turbines firing CO2-rich gas with low air-excess provides economic leverage in terms of greater power generation and carbon capture benefits since air-compression power and flue-gas flowrate are reduced lowering post-combustion capture costs. Offshore and Onshore Gas-to-Wire-CCS were evaluated to evince the best global solution: subsea electricity transmission for offshore generation versus subsea gas/CO2 pipelines for onshore generation. Both have positive net values after 11 years of payback-time, in which the Offshore Gas-to-Wire-CCS was deemed as more sustainable. Thermodynamic analysis unveils 35.5% and 36.2% thermodynamic efficiencies of Offshore and Onshore Gas-to-Wire-CCS indicating thermodynamic superiority of the latter. Lost-work results identified the greatest equivalent-power destruction sinks as the gas-combined-cycle (85%) and post-combustion capture (10%). Offshore Gas-to-Wire-CCS is better at medium-capacity around 600 MW and medium-terms, but Onshore Gas-to-Wire-CCS is unbeatable at high-capacity and long-terms since onshore investment is cheaper, more durable, much less footprint-dependent, and much inferior per MWh.