Innovation in Offshore Separation Process

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Courtesy of Sulzer

CLOV is a deep-sea oil production project offshore Angola. Sulzer helped to lower the cost of the floating production, storage, and offloading (FPSO) ship. There, Sulzer’s patented distributor technology and state-of-the-art pumps are brought to life by Total’s innovative wash tank process. This combination achieves significant cost savings on the FPSO design.

With a processing capacity of 160 000 barrels per day of oil and 230 million cubic feet per day of natural gas, CLOV is one of the largest FPSOs in the world. The CLOV FPSO, operated by Total, is 305 meters long and 61 meters wide.

Innovative oil-cleaning process

Thanks to Sulzer’s high-performance separation technology, the oil-cleaning process achieves commercial oil specifications with processing tanks integrated into the hull of the FPSO vessel. Water and salt are removed from the oil in the wash and desalting tanks. For this cleaning process, Sulzer designed specific, innovative static mixers and inlet distributors. 

Design studies performed by Sulzer for CLOV

Sulzer performed a design study for a preliminary sizing of the mixer and inlet distributor. Two key design aspects helped to meet the target performance of the wash tank process: 

  • The static mixers, which provide optimum mixing of the oil / water phases.
  • The inlet distributors, which optimize the use of the separation section in the hull and improve the water-in-oil content at the tank outlet.

A computational fluid dynamics study (CFD) was performed to understand the influence of FPSO motion on the tank and separation process. The results of this CFD analysis helped to finalize the design of the static mixers and inlet distributors. The internal elements that Sulzer designed create optimally sized droplets of oil. Thus, better separation is achieved even under motion conditions. The technology lessens the required topsides equipment, which leads to significant weight reduction and makes it ideal for an FPSO installation, where it benefits from the large hull size.

Sulzer was able to draw from its extensive experience for this FPSO application, including: 

  • Pilot plant tests, under both static and motion conditions, dating back to the 1980s.
  • Understanding instrumentation, sand handling, and mechanical arrangements for the offshore environment. 
  • Cooperating with the Technical University of Berlin to test various wash tank distributor geometries to achieve best possible water / oil separation.

The construction of the CLOV FPSO was completed in 2014, and oil production started successfully. The technology has been in operation also on Usan and Pazflor FPSOs, and it will be delivered to Moho Nord floating production unit (FPU), Martin Linge floating storage and offloading ship (FSO), and Egina FPSO; all being assets operated by Total.

Fig. 1 Liquid distributors for wash tank process.

Pumping solutions for critical services

Total selected Sulzer to provide pumps for the CLOV wash tank process. In addition Sulzer supplied all of the topsides process pumps including the water injection system. These pumps are expected to operate continuously in the topsides of the FPSO. Therefore, they are subject to the pitch and roll movements of the ship, and they have to withstand challenging operating conditions. Sulzer pumps are designed for use in harsh offshore environments and are compliant not only with the basic API (American Petroleum Institute) standards but also with more-exacting specifications of Total.

To the CLOV FPSO, Sulzer delivered two BB5 water injection pumps (8 MW variable-speed-driven, high-pressure barrel casing pumps). Sulzer also supplied all of the topsides API 610 process pumps including large BB2 pump sets that deliver deaerated seawater to the sulfate removal unit membranes to treat the seawater prior to injection. These API 610 pumps are employed for critical services ranging from dead oil circulation and delivering cooling and heating media across the entire topsides, plus process duties in the oil train to separate and treat the crude oil before its transfer to shore.

Sulzer has also delivered critical API 610 pumps, including the wash tank BB2 transfer pumps, to similar Total projects executed since CLOV, including Moho Nord FPU, Kaombo FPSO, Martin Linge platform and also Egina FPSO, currently under construction in the SHI shipyard at Goeje Island, South Korea.

Fig. 2 Sulzer BB2 pump set for the CLOV project.

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