The Mero-3 FPSO is among the largest deepwater oil production vessels, using advanced technology and engineering to boost oil recovery, cut emissions and improve efficiency in Brazil's Santos basin. Siemens Energy supplied topside modules, power generation, compression, and electrical systems, showcasing the importance of FPSOs in global energy and sustainability efforts.
N. JINDAL, V. LUGOVKIN, and G. SACHERO, Siemens Energy
FPSOs have become increasingly critical to the recovery of offshore oil and gas reservoirs and, in turn, are essential to meeting global energy demand. The operational advantages provided by FPSOs (e.g., ability to operate in a wide range of water depths, fast-track development, conversion possibilities, storage capacity, etc.) make them particularly well-suited for remote, stranded and/or deepwater reserves, where the development and installation of subsea infrastructure to transport oil and gas is not economical. Projected breakeven prices for many FPSO projects today are under $50/bbl, and few are above $70/bbl.
Despite their advantages, FPSOs present challenges in topsides design. This is especially the case for vessels operating in sour field developments or where enhanced oil recovery (EOR) techniques are utilized. On these projects, production equipment configurations can be very complex. As a result, implementing topsides packages that minimize footprint and weight while still meeting electrical and mechanical power requirements can be a challenge. The increasing focus from operators on carbon emissions and sustainability further complicates this task.
In recent years, Siemens Energy has taken strategic steps to optimize its electrical and rotating equipment solutions to meet the demands of modern FPSOs. This article highlights the company’s role in the Mero-3 field development project in the Santos basin (offshore Brazil) and discusses the unique approach that was adopted to reduce project risk and achieve maximum oil production.
MERO-3 OVERVIEW
The Mero field lies roughly 180 km off the coast of Brazil in the Libra Block of the pre-salt area of the Santos basin.
Launched in August 2020, the Mero-3 field includes 15 wells connected to the Marechal Duque de Caxias FPSO unit (operated by MISC Berhad, Fig. 1), with a production capacity of 180,000 bopd, storage capacity of 1.4 MMbbls, and total gas handling capacity of 440 MMscfd.
It is the first FPSO in the world that plans to use High-Pressure Separation (HISEP) technology, an innovative solution that separates CO2-rich gas from production streams and reinjects it back into the reservoir, thereby reducing greenhouse gas emissions. The FPSO is also equipped with Water Alternating Gas (WAG) reinjection technology, as well as stripping and reinjecting CO2 from fuel gas production, with a capacity to compress up to 48 MMscfd of CO2.
Marechal Duque de Caxias is one of the largest ultra-deepwater FPSOs in the world. The vessel is chartered to Brazil’s national oil and gas company, Petrobras, on behalf of the Libra Consortium, which developed the Mero unitized field. Mero field is operated by Petrobras (38.6%) in partnership with Shell Brasil (19.3%), TotalEnergies (19.3%), CNPC (9.65%), CNOOC (9.65%) and Pré-Sal Petróleo S.A. (PPSA) (3.5%), representing the government in the non-contracted area.1
TOPSIDES SOLUTION SCOPE
MISC Berhad contracted Siemens Energy to supply a significant portion of the topsides for the Marechal Duque de Caxias FPSO. This included complete engineering, procurement and construction (EPC) work for eight topside modules consisting of various equipment packages:
2 x power generation modules (Fig. 6): Four SGT-A35 gas turbines (Fig. 2)
1 x CO2 compression module: Two electric motor-driven CO2 compressors
2 x injection compression modules: Three injection compressors driven by SGT-A35 turbines
1 x electrical house module: MV switchgear, LV switchboards, transformers, busduct, electrical control and management system (ECMS), and auxiliary systems
1 x DATUM compressor (Fig. 3): Two electric motor-driven LP compressors
Gas treatment module: Gas processing and treatment packages for fuel gas conditioning, CO2 removal, dew point control, and tri-ethylene glycol (TEG).
POWER ISLAND
The power island for the FPSO features four SGT-A35 gas turbine generators, each producing 34 MW of power. The SGT-A35 turbine (Fig. 2) has an extensive track record in offshore oil and gas, as well as other industrial applications. More than 800 units have been installed worldwide, totaling nearly 50 million hours of service.
High power density is one of several advantages of the Module E-House. This is achieved through a unique system architecture, which incorporates a lightweight, aeroderivative-free power turbine module optimized to operate at synchronous speed to a 2-pole A/C generator. In this configuration, the free power turbine can directly drive an electrical generator at either a 60-Hz or 50-Hz frequency, eliminating the need for a step-down gearbox and resulting in substantial weight and space savings. Compared to its predecessor, the aeroderivative turbine package is 30% lighter.
In addition, the SGT-A35 turbine can be restarted at any time following a shutdown from any condition, without delay due to "hot lockout" conditions, allowing power to be restored quickly and minimizing the risk of downtime. The turbine can also reliably operate on a range of gaseous and liquid fuels. This includes lean fuels containing natural gas diluted with more than 40% CO2 and more than 50% N2. Adaptations can be made to support 100% hydrogen or methanol operation.
A waste heat recovery unit (WHRU) is installed on the gas turbine exhaust side. It consists of four circular, vertical CiBAS WHRU models, each generating 26.34 MW thermal for hot water and other topside process modules. The units are constructed with SA 335 P11 material for enhanced durability and efficiency.
MAIN INJECTION, CO2 COMPRESSORS, AND LP COMPRESSOR TRAINS
Three additional SGT-A35 gas turbines are being used to (mechanically) drive high-pressure DATUM centrifugal injection compressors. Compression modules (Fig. 5) can accommodate multiple process stages and side streams within each casing, depending on process requirements, including intercooling. All compressor internals are arranged as a bundle (i.e., cartridge) that can be pulled horizontally out of the casing to allow easy access for inspection and maintenance. This configuration eliminates the need to remove gas piping. Optional adjustable inlet guide vanes, located in front of the first impeller, can be installed to optimize energy efficiency under part-load conditions.
The SGT-A35 models, which provide horsepower for the compressors, differ slightly from the power generation turbines in that the power turbines use a gearbox.
Siemens Energy’s scope also included two electric motor-driven CO2 compressors and two electric, motor-driven low-pressure compressors.
ELECTRICAL SYSTEMS AND ECMS
The modular E-House (Fig. 4) for the Mero-3 FPSO is a prefabricated electrical substation, fully equipped with medium-voltage switchgear, low-voltage switchboards, busduct and auxiliary equipment.
As part of the electrical scope, Siemens Energy was also responsible for the ECMS, which provides monitoring and supervision for the power generation and distribution network, including load management for the FPSO facility’s topsides and marine operations. The FPSO operator can utilize the ECMS to closely monitor power usage and generate detailed performance reports, which is crucial for tracking equipment energy consumption and optimizing operations to reduce emissions and enhance sustainability.
The capabilities provided by the ECMS are part of a broader effort to incorporate advanced process automation and enhance the overall process efficiency of the FPSO via real-time monitoring of key performance indicators.
REDUCING EXECUTION RISKS AND SIMPLIFYING INTERFACE MANAGEMENT
The topsides design of large, deepwater FPSOs that operate in fields with EOR can be highly complex. The sheer size of the rotating equipment scope (in this case, nearly half of all topside modules) often makes it impractical for a single OEM or integrator to handle the EPC for the power island and electrical auxiliaries, as well as compression trains. The single-source approach adopted on Mero-3 is unique in this regard. It afforded several benefits, including lower execution risk and simplified interface management by reducing the number of vendors involved with the project.
The modules were designed in Singapore and fabricated in China. Packaging took place at Siemens Energy’s manufacturing and service facility in Santa Barbara d’Oeste in São Paulo province. The use of the facility is crucial to the Mero-3 project, which has local content requirements for engineering, machinery and equipment, as well as construction, integration and assembly. The facility was commissioned in 2013 and has played a critical role in meeting local content mandates established by the Brazilian National Petroleum Agency on several major oil and gas development projects in South America.
The EPC scope for the topside modules was completed with no lost time incidents, clocking an impressive six million safe man-hours worked. Weight control and optimization were key priorities for the FPSO. The total weight reduction, from the original design of all eight modules, was roughly 1,000 tons.
Siemens Energy’s global network supported MISC throughout the entire project lifecycle, including construction, commissioning, sail-away, and, ultimately, FPSO operation.
CONCLUSION
Over the last 20 years, a significant portion of global offshore oil exploration, drilling and production has shifted from relatively accessible shallow waters to increasingly deep and ultra-deep waters. Considerable investment in fields offshore Brazil (and other regions) has driven demand for FPSOs, and this trend is likely to continue over the next decade.
Modern FPSO vessels have made it increasingly cost-effective for operators to exploit oil and gas resources in deeper waters and harsher environments. However, their design and development present technical challenges. Advances in the design, engineering and package integration of key rotating equipment and electrical packages, such as gas turbines and compressors, e-Houses and others, have helped the industry meet evolving requirements for electrical and mechanical power, decarbonization, safety and uptime.
First oil from Mero-3 was achieved in October 2024. Peak production was reached in May 2025. WO
REFERENCE
MISC
NAVNEET JINDAL, is head of Modules Business at Siemens Energy and a certified Project Director, based in Singapore. He has over 27 years of experience in the energy sector, specializing in integrated and decarbonized project portfolios. Mr. Jindal has a proven track record in managing large-scale EPC projects, driving innovation in renewable energy solutions, and advancing modular execution strategies.
VICTOR LUGOVKIN is a project manager with the Project Entity team for Siemens Energy, based in Singapore. With 15 years at Siemens Energy, he brings extensive experience in managing complex EPC scopes and specializes in modules for major energy projects.
GIUSEPPE SACHERO is the global head of Oil & Gas and Chemicals for Electrification, Automation, and Digitalization at Siemens Energy, based in Italy. He leads industrial solutions focused on industry decarbonization. With over two decades of experience, Mr. Sachero has held various leadership roles, driving business development, strategic planning, sales, and execution in the energy sector across global markets.