The first subsea horizontal electrical submersible pumping booster system is scheduled for installation later this year in the Gulf of Mexico. The installation will be the first use of a horizontal ESP-based booster system in ultra deepwater.
Subsea ESP systems can operate effectively, but intervention expense is a concern offshore. As a result, Baker Hughes’ Centrilift designed an ESP subsea booster system in a horizontal configuration to reduce installation and intervention expenses.
The horizontal boosting system is a modular, self-contained ESP cartridge consisting of a horizontal, open-framed structure to contain the production tubing, two ESP systems, the electrical penetrator connections, and the fluid connections to tie into the subsea flowlines. Subsea power to the ESP system is to be wet-mated using an ROV.
The production tubing linking the two Centrilift ESP systems loops back and forth with the cartridge framework. Two ESP systems were necessary to maximize the needed pressure within the minimum length and weight footprint. The pumps are hydraulically in series, but not mechanically connected to each other. Rather than lying end to end, the ESPs are connected by hairpin turns in the production tubing. The side-by-side pump layout reduced pump cartridge length from 200 ft (61 m) to about 90 ft (27 m). Because both pumps are in a shorter frame, weight also was reduced. Centrilift used AutographPC design software to develop the pumping systems.
The ESP cartridge design makes the booster systems easier to adapt to existing subsea infrastructure and allows faster, easier, less expensive installation or replacement. The ESP booster system becomes a permanent seafloor structure and is easy to change out when necessary. Plus, all preparations to install the ESP cartridge can be made onshore, to reduce surface work vessel time.
The ESP systems include 17 stage mixed flow pumps, which can handle flow rates up to 20,000 b/d. The motor on the first ESP system in series will be monitored by a Baker Hughes Sureflo HARVEST sensor pod. The pod will gather pump data such as intake pressure, intake temperature, motor winding temperature, and vibration. The second ESP system in series will be identical to the first except for the second system will have two sensors – one at the bottom of the motor and one at the pump discharge. The bottom sensor works like the one in the first system while the second sensor will measure discharge pressure and discharge temperature. There will be two sensor data lines, one for each system.
To resist corrosion and increase reliability, special metallurgy is used throughout these systems. The variable speed drive surface control systems will be housed in air-conditioned structures on the FPSO.
The horizontal boosting systems are planned for installation in the third quarter of this year and first oil from the field is planned by year-end.
Deepwater vertical application
Baker Hughes already has installed Centrilift XP ESP systems in two vertical subsea boosting stations on the seabed at Shell’s Perdido field in the Gulf of Mexico in 8,000 ft (2,438 m) of water. The pumping systems at Perdido are designed to boost up to 125,000 b/d of fluid. Baker Hughes contracted for five enhanced run life systems, engineering design, and qualification and testing services for Perdido in 2007. The remaining three ESP systems are scheduled for installation later this year.
Horizontal electrical pump under construction.
Perdido, which began producing in March, is the world’s deepest application of a full-scale seabed separating and boosting system. The 1,600-hp ESP systems – designed to lift liquids 8,000 ft from the seafloor to the production platform – are installed in five, 350-ft (107-m) long caissons connected directly to the platform’s production risers. The caissons are located near the spar production facility. Each caisson has cylindrical-cyclonic gas separation systems to separate natural gas entrained in the fluids before the fluids enter the ESP system. The boosting systems handle production from three subsea satellite fields (Great White, Silvertip, and Tobago) tied back to the Perdido spar.
Each Perdido ESP has remote, real-time monitoring and control, and an ESP cable/control line cutting tool in the event the tubing inside a production riser must be cut and retrieved.
“Baker Hughes has made a major contribution to achieving first production at two of Shell’s top deepwater projects. Reliable ESP performance is critical to the overall success of Perdido in the Gulf of Mexico and BC-10 offshore Brazil,” says Ernst den Hartigh, vice president of technical support, Shell Deepwater. “Baker Hughes has consistently demonstrated a commitment to project success that began with a full-scale technology qualification and demonstration effort in 2006 and has continued through installation and startup. Baker Hughes’ perseverance, commitment to quality and excellence in engineering design and application were major factors in helping us achieve this success,” he notes. •
