Optimizing the power hub of offshore multi-platform for oil and gas production

Offshore oil and natural gas production is an energy-intensive activity and is responsible for the emission of significant amounts of carbon dioxide into the atmosphere. The main emitting source is the simple-cycle gas turbines (SCGT) of the utility system which supplies heat and power to the production platforms. Severe vessel area and weight constraints are often cited as the main reason why production platforms are unable to allocate high-efficiency combined-cycle gas turbines (CCGT) common in land-based power plants. Published work suggests that in production development projects of giant offshore oil fields, the thermodynamic efficiency of the utility system may be increased significantly, without prejudice to project economic viability, through an additional vessel dedicated to generating power in CCGT. The best results are obtained when the power demand is split between the power hub and local gas turbines which are used in cogeneration mode to additionally produce heat for separation purposes. Therefore, this work proposes a methodology for optimizing the power block of the power hub. The first step is the selection of combined cycle configurations from the commercially available aero-derivative gas turbines. At sequence, evolutionary algorithms are used in the multi-objective optimization (MOO) of the steam bottoming cycle, whose objective is to obtain the configurations that produce the best results in terms of atmospheric CO2 emissions, occupied area, and capital cost. A method is then proposed to select the best solution from the non-dominated solutions that compose the Pareto front, taking into account the constraints imposed by the vessel of the central power plant and the objectives to be optimized. The power hub solution presented average exergy efficiency 8.2p.p. above the conventional, thus reducing the fuel gas consumption by 1.74 million ton and consequently avoiding the emission of 4.75 million ton of CO2. Finally, in the context of growing environmental concern and taxation of CO2 emissions, this work contributes to highlighting the advantages of the central power plant in future maritime production development projects in large oil and gas fields.