Thermo-Economic Modelling and Process Integration of CO₂-Mitigation Options on Oil and Gas Platforms

The offshore extraction of oil and gas is an energy-intensive process associated with large CO₂ and CH4 emissions to the atmosphere and chemicals to the sea. The taxation of these emissions has encouraged the development of more energy-efficient and environmental-friendly solutions, of which three are assessed in this paper. The integration of steam bottoming cycles on the gas turbines or of lowtemperature power cycles on the export gas compression can result either in an additional power output, or in a greater export of natural gas. Another possibility is to implement a CO₂-capture unit, which allows recovering CO₂ that can be used for enhanced oil recovery. In this paper, a North Sea platform is considered as case study, and the site-scale retrofit integration of these three options is analysed, considering thermodynamic, economic and environmental performance indicators. The results illustrate the benefits of valorising the waste heat recovered from the exhaust gases, as the total CO₂-emissions can be reduced by more than 15 %. Exploiting low-temperature heat seems feasible, although more challenging in retrofit situations. Integrating CO_2-capture appears promising with a CO₂-avoidance cost between 23 and 29 $/tCO₂ for the chosen economic assumptions.