Energy efficiency, sustainability, and operating cost optimization of an FPSO with CCUS: An innovation in CO2 compression and injection systems

Production in FPSO (Floating Production Storage and Offloading) is challenging due to its energy demand, operating cost, and environmental impact. In particular, the composition of the reservoir fluid, which varies along with the life of a well, greatly affects the operation and production of the FPSO. Any optimization study aiming at reducing energy consumption, sustainability, and operating costs during the life span of a well should take this fluid variability into account. Additionally, a typical FPSO operating in the Brazilian deep-water oil regions requires process fluid with high CO2 content. Therefore, a new FPSO process plant configuration comprises a membrane-based CCU (Carbon Capture and Utilization) system integrated with an MEA-based CCS (Carbon Capture and Storage) system and a CO2 compression unit with fewer compressors and one injection unit is proposed. Subsequently, automated optimization procedures consisting of a hybrid algorithm (NSGA-II + AfilterSQP) are implemented to optimize the energy efficiency, sustainability, and operation costs of the FPSO under consideration. More than 25 thermodynamic and structural design variables are considered as input variables in the optimization procedures. The results presented a significant reduction of up to 10.1% (2.9 MW) in overall power consumption, mitigation of CO2 emissions of up to 47 kg/h, a decrease of up to 3.9% (2.4 million USD/year) in operating cost, and an improvement of up to 53.5% in total heating and cooling demand of the FPSO, which means a reduction of 3.8 × 109 (kJ/h). In a proposed system with one CO2 injection unit, optimization results in the mitigation of total power consumption of up to 1.4 MW, a decrease in capital cost of 10 million USD, a reduction in operating cost of 50 million USD/year, and an increase of 4.4% in CO2 removal efficiency.