Postcombustion CO2 Capture in Offshore FPSO Systems: Lifetime Simulation and Assessment of Perspectives and Challenges

Abstract

The present study evaluated the technical impact of incorporating an amine-based postcombustion CO2 capture unit (CCS) into FPSO (floating production, storage, and offloading) units throughout their entire operational lifetime, considering different processing capacities (100 and 250 kbpd of liquids), different gas-oil ratios (150 and 300 Sm3/Sm3), and different reservoir fluid CO2 contents (3 and 60%, molar basis). A total of 192 process simulations were performed, including simple cycle (SC), simple cycle with CCS (SC + CCS), and combined cycle with CCS (CC + CCS) configurations. The results demonstrated challenges associated with CCS unit underutilization: an average underutilization of 27% was observed, exceeding 60% during the final years of operation in all of the simulated cases. Zero underutilization was achieved in all cases only when the nominal CCS capacity was defined as 30% of the maximum exhaust gas flow rate produced in each case. For cases in which the CCS unit was designed with a full-flue-gas capture ambition for the FPSO, i.e., capable of processing up to 100% of the maximum exhaust gas flow rate generated in each case, the required CCS capacities reached up to 12.5 and 22 MMSm3/day in the SC + CCS configuration for fluids containing 3 and 60% CO2, respectively, and up to 12.1 and 18.2 MMSm3/day in the CC + CCS configuration. Replacing the SC configuration with the CC configuration in the presence of CCS resulted in reductions in cumulative emissions (over the entire operational lifetime) of up to 8.2 and 96 kt for the cases with 3 and 60% CO2, respectively. Considering the limitations associated with heat recovery availability (without the inclusion of an additional furnace) for the implementation of CCS and/or combined-cycle systems, it was observed that for the field containing 60% CO2, cumulative CO2 recovery over the installation lifetime ranged from 79 to 90% under the full-flue-gas capture design scenario. Integration of an auxiliary furnace provided limited benefits for the SC + CCS configuration. For the field containing 3% CO2, the cumulative CO2 recovery ranged from 38 to 80% across the simulated cases.