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

Abstract

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.

Assessment of an Isolated Offshore Power Grid Based on the Power Hub Concept for Pre-Salt Oil and Gas Production

“…These areas are located 200 km from the coast in water depths that can reach 2,000 m. As an alternative to reduce the GHG emissions from the offshore O&G ultra-deep waters activities, a power hub with local power generation can be employed. This concept was initially proposed [8] and further optimized for the Brazilian pre-salt basin case [9]. It consists of an additional offshore platform exclusively for power generation, without any productive processes on board.…”

“…Concerning the possible adoption of the power hub, researchers have focused their attention to the exergy analysis [3] and emission studies [12]; optimization of the power generating module [9], [13]; its integration with CCS [11] and its economical evaluation [12], [14]. However, in the literature, there are only a few and not very up-to-date papers that investigate the electrical system stability of modern and isolated offshore power grids.…”

Offshore Utility Systems for FPSOs: A Techno-Environomic Assessment Considering the Uncertainty About the Natural Gas Price

“…In order to tackle these problems, different alternatives have been proposed, ranging from the electrification from shore (Myklebust et al, 2017) to the conception of a power hub composed of more efficient combined cycles (Vidoza et al, 2019). Some studies proposed a power hub without carbon capture aiming to centralize the electricity generation for a number of FPSOs (Vidoza et al, 2018).…”

“…In order to tackle these problems, different alternatives have been proposed, ranging from the electrification from shore (Myklebust et al, 2017) to the conception of a power hub composed of more efficient combined cycles (Vidoza et al, 2019). Some studies proposed a power hub without carbon capture aiming to centralize the electricity generation for a number of FPSOs (Vidoza et al, 2018). As a result, relatively high power generation efficiencies (53%) and an appreciable reduction of CO 2 emissions (19%) are achieved for a scheme that implements two levels of steam pressure, three gas turbines and only one heat recovery steam generator (HRSG).…”

Compact Steam Bottoming Cycles: Minimum Weight Design Optimization and Transient Response of Once-Through Steam Generators

“…Nord and Boland evaluated the design of combined cycles for off-shore oil and gas installations, concluding that the efficiency could be increased by 10-13% and significant CO 2 emissions can be reduced (20-25%), but the main disadvantage is the heavy designs, which result in 60-70% weight to power ratio increase in comparison with simple cycle power plants (Nord and Olav, 2013). Vidoza et al (2019) proposed a floating off-shore platform for lower fuel consumption and CO 2 emissions, in a configuration with several gas turbines in parallel connected each to a heat recovery steam generator (HRSG) and feeding a common steam bottoming cycle. Other nonconventional working fluids have been evaluated for bottoming cycles, namely air bottoming cycles (Pierobon and Haglind, 2014), CO 2 cycles (Walnum et al, 2013;Zhang et al, 2018), and organic Rankine cycles (Tchanche et al, 2011;Pierobon et al, 2013;Lecompte et al, 2015;Nami et al, 2018).…”