Design and optimization of power hubs for Brazilian off-shore oil production units

A worldwide trend to reduce greenhouse gases emissions has encouraged researchers to study more efficient solutions in oil and gas Industry. Most offshore units are energized by equipment operating at low loads, increasing environmental impact. This work aims identifying optimal designs and layouts of a combined cycle floating power hub tailored for offshore oil production applications.

The Brazilian pre-salt basin which forecast high fuel gas production is taken as a case study. A model was developed, integrating the design of the gas turbine, heat recovery units, steam turbine and condenser. Genetic algorithms were applied in two optimization approaches, single-objective and multi-objective.

Three parameters were evaluated: equipment purchase cost, thermal efficiency and total weight. The results of the multi-objective optimization indicated that dual-pressure arrangements, featuring 3 gas turbines, 1 heat recovery steam generator and 1 steam cycle, could be an attractive design solution for power hubs.

This arrangement has a low cost and weight, while the thermal efficiency is maintained at a reasonably high level (around 53.2 %). Moreover, results indicated that CO2 emissions may be reduced by 18.7 % to 27.2 % at design point and 19% for the power hub lifetime, when compared with the conventional energy supply scenario.